The Fiber Society 2012 Fall Meeting and Technical Conference

in partnership with

Polymer Fibres 2012

present

Rediscovering Fibers in the 21st Century

November 7–9, 2012

Conference Chairs

Stephen Eichhorn, University of Exeter Cheryl Gomes, QinetiQ North America, Inc. Gregory Rutledge, Massachusetts Institute of Technology

Venue

Boston Convention and Exhibition Center Boston, Massachusetts, USA

Program

Tuesday, November 6

1:00 PM–5:00 PM Governing Council Meeting, Room 160C 5:00 PM–6:00 PM Early-Bird Registration and Reception, Room 102A

Wednesday, November 7

8:00 Registration and Continental Breakfast 8:40 Welcoming Remarks and Announcements Gregory Rutledge, Stephen Eichhorn, Co-chairs Cheryl Gomes, Co-chair and President, Fiber Society

Morning Session

9:00 Keynote Speaker: Ray H. Baughman, University of Texas at Dallas, USA High-Performance, Electrolyte-Free Torsional and Tensile Carbon Nanotube Hybrid Muscles (Room 104A)

9:40 Break (Room 102A)

Room 104A Room 104C Session: Carbon Fibers and Session: Thermal and Spectroscopic Composites Properties Gregory Rutledge, Chair Janice Gerde, Chair 10:00 Use of Raman Spectroscopy to Resolve Atomic Force Microscope-Based Infrared Analysis of Structure of Graphene- Spectroscopy of Single Fibers Coated Fibers Michael Lo1, Qichi Hu1, Curtis Marcott2, Ian R. Hardin and Susan Wilson, Craig Prater1, and Kevin Kjoller1, 1Anasys University of Georgia Instruments Corp., 2Light Light Solutions 10:20 Carbon Fiber from Extracted The Response of a - Fabric to Commercial Softwood Lignin High Heat Flux D.A. Baker, D.P. Harper, and T.G. Thomas Godfrey, Margaret Auerbach, Gary Rials, University of Tennessee at Proulx, Pearl Yip, and Michael Grady, U.S. Knoxville Army Natick Soldier RDE Center 10:40 Electrospun Carbon Nanofibers from A Study and a Design Criterion for Multilayer Kraft Lignin Structure in Perspiration-Based Infrared Omid Hosseinaei and Darren Baker, Camouflage University of Tennessee at Knoxville Xia Yin1, Qun Chen2, and Ning Pan1, 1University of California at Davis, 2Tsinghua University 11:00 Mesoporous Activated Carbon Thermal Protective Performance of Protective Nanofiber Synthesis from Catalytic Clothing Upon Steam and Hot Liquid Splash Graphitization of Polyacrylonitrile/ Farzan Gholamreza, Guowen Song, and Mark Cobalt Sulfide Composite Ackerman, University of Alberta (presented Yakup Aykut1, Behnam Pourdeyhimi2, by Shiqi Liu) and Saad Khan2, 1Uludağ University, 2North Carolina State University 11:20 Electrically Conductive Fibers with Thermal and Flame Retardant Behaviors of Carbon Nanotubes: 3D Analysis of Cotton Fiber Treated with Phosphoramidate Conductive Networks by Electron Derivatives Tomography Thach-Mien Nguyen, SeChin Chang, and Wilhelm Steinmann, Johannes Brian Condon, U.S. Department of Wulfhorst, Thomas Vad, Gunnar Agriculture Seide, Thomas Gries, Markus Heidelmann, and Thomas Weirich, RWTH Aachen University 11:40 [Open] Characterization of Component Fibers in Military Using Pyrolysis-GCMS Pearl Yip, U.S. Army Natick Soldier RDE Center 12:00 Lunch On Your Own: Expo: Poster Setup (Room 102A)

Afternoon Session

1:30– Student Paper Competition Room 104A Chair: Michael Ellison 2:45 Xianwen Mao, MIT: Electrospun Carbon Nanofiber Webs with Controlled Density of States for Sensor Applications Hua Zhou, Deakin University: Durable Superhydrophobic Fabrics Prepared by Surface Coating of Nanoparticle/Elastomeric Composite Xiaodan Zhang, Georgia Tech: Flexible and Transparent Fiber-Based Ionic Diode Fabricated from Oppositely Charged Microfibrillated Cellulose

2:45 Break (Room 102A)

3:00– Keynote Speaker: Dr. Mary Boyce, Massachusetts Institute of Technology, USA 3:40 Mechanics of Nonwoven Fibrous Mats: Structure Evolution and Elastic- Deformation (Room 104A) Room 104A Room 104C Session: Clean Water/Clean Energy Session: Mechanical Properties Konstantin Kornev, Chair Stephen Eichhorn, Chair 3:50 Electrospun Nanofiber Derived TiO2 Developing an Environmentally Friendly Active Layer for -Sensitized Solar Isothermal Bath to Obtain a New Class of Cell Applications High-Performance Fibers Xueyang Liu1, Jian Fang1, Mei Gao2, H. Avci, H.J. Yoon, and R. Kotek, North and Tong Lin1, 1Deakin University, Carolina State University 2CSIRO Materials Science and Engineering 4:10 Photovoltaic Fiber Having Polymer The Mechanics and Tribology of Electrospun Anode and Inverted Layer Sequence PA 6(3)T Fiber Mats İ. Borazan1, A. Bedeloğlu2, and A. Matthew Mannarino and Gregory Rutledge, Demir1, 1İstanbul Technical MIT University, 2Dokuz Eylül University 4:30 Optimizing Fiber-Based Bioconversion On the Design Method of Lightweight Media for Ammonia/Water Bio- Construction Materials: Structural Remediation Characteristics-Tearing Strength Relationship Yong Kim and Armand Lewis, Yusuf Ulcay1,2 and Fatih Suvari1, 1Uludağ University of Massachusetts at University, 2Bursa Technical University Dartmouth 4:50 3D Woven Fabrics as Filtration Media Continuous Dynamic Analysis: Evolution of in a Membrane Bioreactor for Storage and Loss Modulus in Fibers as a Wastewater Treatment Function of Strain Fang Zhao, Bubi Jing, Hong Chen, Sandip Basu and Jennifer Hay, Agilent Fujun Xu, Lan Yao, and Yiping Qiu, Technologies Donghua University

5:20– Poster Session and Reception (Room 102A) 7:00

Thursday, November 8

8:00 Continental Breakfast (Room 102A)

Morning Session

9:00 Keynote Speaker: Dr. David Weitz, , USA Biopolymer Networks: How Fiber Structures Provide Rigidity to the Cell (Room 104A)

9:40 Break (Room 102A)

Room 104A Room 104C Session: Natural Fibers Session: Surface Properties Ian R. Hardin, Chair Michael Ellison, Chair 10:00 Soybean Biorefinery Model: Butterfly-Inspired Fiber-Based Nanofluidics Nanofibers, Nanocomposites, Green Konstantin Kornev, Clemson University Composites and More Anil Netravali, Cornell University 10:20 Self-Assembled Nanostructures from Theoretical and Experimental Investigation of Cellulose Nanocrystals Non-Rotationally Symmetrical Droplets on You-Lo Hsieh, University of Fibers California at Davis Jintu Fan1,2, Maofei Mei1, and Dahua Shou1, 1Hong Kong Polytechnic University, 2Cornell University 10:40 Orientation of Cellulose Nanofibers Optimization of Breathable Waterproof Using Magnetic Fields and Wet- Coating Conditions for Minimizing Fabric Stretching Frictional Sound of Korean Military Combat Stephen Eichhorn1, Arthur Wilkinson2, Uniform Fabrics and Tanittha Pullawan2, 1University of Kyulin Lee and Gilsoo Cho, Yonsei Exeter, 2University of Manchester University 11:00 Electrospinning Hyaluronic Acid Functional Coloration to Offer Photo- Caroline Schauer and Laura Toth, Induced Surface Functions Drexel University Gang Sun, Jingyuan Zhou, and Ning Liu, University of California at Davis

11:20 Structure and Mechanical Properties Comparison of Color Properties of CO2 of -Inspired Flow-Assembled Laser-Treated Cotton -Blended Fibers Fabric Before and After Dyeing Seunghwa Ryu1, Greta Gronau1, O.N. Hung, C.K. Chan, C.W. Kan, and Michelle Kinahan2, Sreevidhya C.W.M. Yuen, Hong Kong Polytechnic Krishnaji3,4, David Kaplan3, Joyce University Wong2, and Markus Buehler1, 1MIT, 2Boston University, 3Tufts University 11:40 Submicron Fiber Nonwovens from Development of a Novel Bicomponent Fiber- Ingeo®, a Sustainable Polymer Based PET/PE Composite with Improved Gajanan Bhat1, Kokouvi Akato1, and Interface and Mechanical Performance Robert Green2, 1University of Mehmet Dasdemir1, Benoit Maze2, Nagendra Tennessee at Knoxville, 2 Nature Anantharamaiah3, and Behnam Pourdeyhimi2, Works 1University of Gaziantep, 2North Carolina State University, 3Hollingsworth & Vose

12:00 Lunch On Your Own; Expo

Afternoon Session

1:30 Keynote Speaker: : Dr. Andy Alderson, University of Bolton, UK Auxetic Fibres: History, Applications, and Future Perspectives (Room 104A)

2:10 Break (102A)

Room 104A Room 104C Session: Biology and Health Session: Fiber Processing Caroline Schauer, Chair Rudolf Hufenus, Chair 2:30 Green Engineering of Antimicrobial SiC Fiber Made with Aqueous Binder by Nanofiber Mats Melt Spinning Jessica Schiffman, Katrina Rieger, Alex Lobovsky and Mohammad Behi, Nathan Birch, and Nathaniel Eagan, United Materials Technologies University of Massachusetts at Amherst 2:50 Antimicrobial Finishing of Polyester and High-Performance Polyimide Fibers Cotton Fabrics Prepared by Dry Spinning Technology Idris Cerkez, S.D. Worley, and R.M. Qinghua Zhang, Yuan Xu, Jie Dong, Broughton, Auburn University Chaoqing Yin, Shihua Wang, and Dajun Chen, Donghua University 3:10 The Effect of Needlepunched Nonwoven High-Throughput Needleless Fabric on Controlling Hyperhydricity of Electrospinning of Core-Sheath Fibers Scutellaria Species In Vitro Liquid Toby Freyman1, Xuri Yan1, Quynh Pham1, Culture Systems John Marini1, Robert Mulligan1, Upma M. Taşcan1, J. Adelberg2, A. Taşcan1, N. Sharma1, Michael Brenner2, and Gregory Joshee3, and A.K. Yadav3, 1Zirve Rutledge3, 1Arsenal Medical, 2Harvard University, 2Clemson University, 3Fort University, 3MIT Valley State University 3:30 Amidoximated Bacterial Cellulose as an Coaxial-Free Surface Electrospinning Effective Nanoreactor for In Situ Keith Forward1,2, Alexander Flores1, and Synthesis of ZnO Nanoparticles Gregory Rutledge1, 1MIT, 2California State Weili Hu, Shiyan Chen, Bihui Zhou, and Polytechnic University Huaping Wang, Donghua University 3:50 Textile Heart Valve Prosthesis: Early In Developing Real-Time Control for Vitro Fatigue Performances Electrospinning of Nanofibers: Evaporation Frederic Heim1, Bernard Durand1, and and Measurement Considerations for Nabil Chakfe2, 1ENSISA, 2Hôpitaux Aqueous and Non-Aqueous Solutions Universitaires de Strasbourg Michael Gevelber, Yunshen Cai, Thierry Desire, and Xuri Yan, Boston University 4:10 Investigation into New 3D Fibrous Electro-Centrifugal Nanofiber Spinning Structure for Soles Application Tao Huang, Jack Armantrout, Kevin 1 1 Mouna Messaoud , Antoine Vaesken , Allred, and Thomas Daly, DuPont Laurence Schacher1, Dominique Adolphe1, Jean-Baptiste Schaffhauser2, and Patrick Strehle2, 1ENSISA, 2N. Schlumberger 4:30 Property Evaluation of Diabetic Socks Governing Equations for the Well- Used to Prevent Diabetic Foot Enchanced Electro-Centrifuge Spinning Syndrome Process M.J. Abreu, A. Catarino, and O. Rebelo, Seyed Hosseini Ravandi, Afsaneh Valipouri, University of Minho and Admadreza Pishevar, Isfahan University of Technology 5:00– Fiber Society General Body Meeting (Open to Fiber Society Members Only) 6:00 Room 104A

6:00 Reception (Room 104B)

6:30–10:00 Banquet and Awards Ceremony Ms. Shevy Rockcastle, KVA Kennedy & Violich Architecture Going Soft: Textiles and Resilient Architecture

Friday, November 9

8:00 Continental Breakfast (Room 102A)

9:00 Keynote Speaker: Dr. John F. Rabolt, University of , USA Preparation and Characterization of Multilayer Polymer Nanofibers by Multiaxial Electrospinning (Room 104A)

9:40 Break (Room 102A)

Room 104A Room 104C Session: Nanofibers Session: Sensors and Electrical Properties Michael Jaffe, Chair Phillip Gibson, Chair 10:00 A Historical Perspective on Base Fiber Technologies for Smart Textiles Nanofibers: Can We Make It More R. Hufenus, D. Hegemann, S. Gaan, F.A. Relevant? Reifler, and L.J. Scherer, Empa H. Young Chung, Et Esus 10:20 Electrospun Nanofibers Functionalized Electrical Conductivity of Electrospun with Cyclodextrins and Their Potential Polyaniline and Polyaniline-Blend Fibers and Applications Mats Tamer Uyar, Asli Celebioglu, Fatma Yuxi Zhang and Gregory Rutledge, MIT Kayaci, Zeynep Aytac, and Yelda Ertas, Bilkent University 10:40 Spinning Functional PLA Nanofibers Mechanical and Electrical Properties of for Controlled Release, Protein 66 Nanocomposites Reinforced Capture, and Sensing with Buckminster Fullerene C60 Margaret Frey1, Dapeng Li1,2, Chunhui Reyhan Keskin2, Ikilem Gocek1, Guralp Xiang1,3, and Ebru Buyuktanir4,5, Ozkoc3, Koray Yilmaz2, and Yunus Kamac2, 1Cornell University, 2University of 1İstanbul Technical University, 2Pamukkale Massachusetts at Dartmouth, 3Iowa University, 3Kocaeli University State University, 4Kent State University, 5Stark State University 11:00 Melt Spinning PP: A Formation Model Production of Polymer Filament-Shaped Development of “Hard Plastic” Piezoelectric Sensors for E-Textiles Behavior Applications Michael Jaffe, New Jersey Institute of H. Carvalho4, R.S. Martins1, R. Gonçalves2, Technology J.G. Rocha3, J.M. Nóbrega1, S. Lanceros- Mendez2,5, 1Institute for and Composites, 2Centro/Departamento de Física, 3Dep. Industrial Electronics, 4University of Minho, 5International Iberian Nanotechnology Laboratory 11:20 Characterization of Compressive Chemical Resistance of Poly(3,4- Properties of Electrospun Mats ethylenedioxythiophene) on Textiles Looh Tchuin Choong and Gregory Christopher DeFranco, Qinguo Fan, and Jinlin Rutledge, MIT Cai, University of Massachusetts at Dartmouth 11:40 Fabrication of Composite Tunable Force Sensor Based on Flexible Polyallylamine-Nanodiamond Fibers Polymeric Optical Fibres Marjorie Kiechel, Ioannis Neitzel, Marek Krehel1,2, René Rossi1, Gian-Luca Vadym Mochalin, Yury Gogotsi, and Bona1,2, and Lukas Scherer1, 1Empa, 2 ETH Caroline Schauer, Drexel University Zurich

12:00 Close of Conference: Room 104A

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Poster Presentations

Session Chair: Stephen Michielsen

Room 102A

Zachary Dilworth 3D Volume Representation of Nanowebs

Carole Winterhalter Comparison of Evaporative Resistance of Carbon-Based Chemical Protective Undergarments

Larissa Buttaro Phase Separation to Create Hydrophilic Yet Nonwater Soluble PLA/PLA-b-PEG Fibers via Electrospinning

Meryem Pehlivaner The Effects of Solvents on the Morphology and Conductivity in PEDOT:PSS / PVA Nanofibers

Laura Toth Chitosan Fiber Scaffolds for Craniofacial Bone Tissue Engineering

Fuan He Preparation and Characterization of Organosilicate-Reinforced Electrospun Membrane

Eliza Allen Incorporation and Performance of Molecular Polyoxometalates in Cellulose Substrates

Zhang Jiang Nanoconfinement-Induced Enhancement of Thermal Energy Transport Efficiency in Electrospun Polymer Nanofibers

Yunfei Han Reactivity of Methyl Parathion Degradation with Immobilized Zinc Oxide Nanoparticles

Helder Carvalho Surface Electromyography Using Textile-Based Electrodes

Seyed Ravandi Physical Properties of PLGA Nanofiber with Potential Application Surgical Suture

Kaiyan Qiu Biodegradable Polymer Nanocomposites Using Polyvinyl Alcohol and Nanomaterials

Yunshen Cai Real-Time Control for Electrospun Nanofiber: Experimental Investigation of Electrospinning Physics

Judith Sennett Environmental Aging Study of AuTx® and ® and Fabrics

Phillip Gibson A Design Tool for Clothing Applications: Wind Resistant Fabric Layers

Hua Zhou (presented Durable Superhydrophobic Fabrics Prepared by Surface Coating of by Xue Yang) Nanoparticle/Elastomeric Polymer Composite

Xianwen Mao Electrospun Carbon Nanofiber Webs with Controlled Density of States for Sensor Applications

Xiaodan Zhang Flexible and Transparent Fiber-Based Ionic Diode Fabricated from Oppositely Charged Microfibrillated Cellulose

Laura Lange Polyacrylonitrile-Metal Organic Framework (MOF) Composite Electrospun Nanofibers Designed to Remove Chemical Warfare Agent Simulants from a Solution

Liliana Fontes Thermal and Comfort Measurements of Mattress Protectors Used for Prevention of Pressure Ulcers

Hu Zhang The Influence of Copper (II) Ions on Photostability in the Dry State

David Branscomb Open-Architecture Composite Tube: Design and Manufacture

High-Performance, Electrolyte-Free Torsional and Tensile Carbon Nanotube Hybrid Muscles

Márcio D. Lima1, Na Li1,2, Mônica Jung de Andrade1, Shaoli Fang1, Jiyoung Oh1, Geoffrey M. Spinks3, Mikhail E. Kozlov1, Carter S. Haines1, Dongseok Suh1, Javad Foroughi3, Seon Jeong Kim4, Yongsheng Chen2, Taylor Ware1, Min Kyoon Shin4, Leonardo D. Machado5, Alexandre F. Fonseca6, John D. W. Madden7, Walter E. Voit1, Douglas S. Galvão5, Ray H. Baughman1

1The Alan G. MacDiarmid NanoTech Institute, University of Texas at Dallas, Richardson, TX 75083, USA; 2Centre of Nanoscale Science and Technology, Institute of Polymer Chemistry, College of Chemistry, Nankai University, 300071, Tianjin, China; 3Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Wollongong, NSW, 2522, Australia; 4Center for Bio- Artificial Muscle and Department of Biomedical Engineering, Hanyang University, Seoul, 133-791, South Korea; 5Applied Physics Department, State University of Campinas–UNICAMP Campinas-São Paulo–Brazil, CP 6165 CEP 13081-970; 6Faculdade de Ciências, UNESP–Univ. Estadual Paulista, Bauru, SP, 17033-360, Brazil; 7Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC V6T 1Z4, Canada

[email protected]

ABSTRACT extension to microvalves, mixers, smart phone New electrolyte-free muscles that provide fast, high- lenses, positioners and even toys and intelligent force, large-stroke torsional and tensile actuation are textiles. described, which are based on guest-filled, twist- spun carbon nanotube yarns. Actuation of hybrid yarns by electrically, chemically, and photonically powered dimensional changes of yarn guest generates torsional rotation and contraction of the helical yarn host. Over a million reversible torsional and tensile actuation cycles are demonstrated, wherein a muscle spins a rotor at an average 11,500 revolutions/minute or delivers 3% tensile contraction at 1,200 cycles/minute. This rotation rate is 20 times higher than previously demonstrated for an artificial muscle and the 27.9 kW/kg power density during muscle contraction is 85 times higher than for natural skeletal muscle. Applying well-separated 25 ms pulses yielded 0.104 kJ/kg of mechanical energy during contraction at an average power output of 4.2 kW/kg (four times the power-to-weight ratio of common internal combustion engines). Demonstrations include torsional motors, contractile muscles, and sensors that capture the energy of the sensing process to mechanically actuate. Improved control and large rotational actuation, along with long cycle life and tensile contractions up to 9%, suggest the use of these yarn actuators in medical devices, robots, and shutters, for which shape memory alloys are currently employed, as well as

Auxetic Fibres: History, Applications, and Future Perspectives

Andy Alderson Institute for Materials Research and Innovation, University of Bolton, Deane Road, Bolton BL3 5AB, UK [email protected]

STATEMENT OF PURPOSE/OBJECTIVE thought to arise due to relative motion of segments In this paper, the auxetic effect will be introduced, within a granular microstructure. the range of auxetic materials will be briefly reviewed, and applications based on the unusual On the other hand, the auxetic effect arises at the auxetic property itself, or extreme values of other macro-level in a two-constituent yarn [3]. Upon properties achievable via the auxetic effect, will be stretching of the bifilament yarn, an initially straight, highlighted. The paper will then focus specifically on thick, low stiffness core yarn adopts a helical fibres that have been developed displaying the conformation due to straightening of a thinner, high auxetic effect. This will include their fabrication and stiffness wrap yarn initially wound helically around characterization, mechanisms for auxetic fibre the core. Conventional yarn constituents and existing response, and their applications. Finally, wrapping technology are employed. considerations relating to future development of auxetic fibres will be discussed. AUXETIC FIBRE APPLICATIONS Applications identified for auxetic fibres include: INTRODUCTION  Biomedical sutures and ligaments An auxetic material under tension in one direction  Sensors (mechanical, optical…) becomes thicker in one or more perpendicular  Pull-out resistant fibres in composites directions (Figure 1). This corresponds to a negative  Carbon fibre reinforced composite value of Poisson’s ratio. components having reduced thermal distortion and microcracking

Auxetic fibres have also been incorporated into textile fabrics, giving futher applications such as  Bandages and garments displaying controlled release of active ingredients (e.g. drug and odours)  Blast protection curtains  Wear resitance fabrics

Figure 1: Auxetic material in relaxed and stretched FUTURE PERSPECTIVES states. The development of future fibres having improved or optimized properties, such as reduced diameter, Auxetic materials exist in a variety of classes (metals, increased stiffness, high temperature response and polymers, composites and ceramics), spanning the homogeneity, may be achieved by incorporating nanoscale to the macroscale, on both natural and alternative polymers/materials into the existing man-made forms [1]. They are attracting interest due processing routes. Ultimately, however, it will be to their unusual mechanical response, and also necessary to develop fibres where the auxetic because other material properties can attain extreme property arises due to molecularly-engineered (high or low) values by virtue of possessing the nanostructures. Strategies for achieving this have auxetic effect. Examples include enhanced been based on scaling down structures known to lead indentation resistance, fracture toughness, and to the auxetic property at the macroscale and vibration damping. microscale (e.g. honeycombs and nodule-fibril networks) to the nanoscale (e.g. molecular AUXETIC FIBRES honeycombs and liquid crystalline polymers, There are two main types of auxetic fibres that have respectively) [4,5]. Alternatively, the study of auxetic been produced to date. In one, an intrinsically auxetic behaviour in naturally-occurring nanostructures, such monofilament can be produced using conventional as inorganic auxetic single-crytal silica (- melt spinning of thermoplastic polymer powder at an cristobalite) [6] and organic auxetic crystalline extrusion temperature close to the polymer melt onset cellulose (I and II forms) [7,8], will provide clues as temperature [2]. In this case the auxetic effect is to the structures and mechanisms to be developed in [4] Evans, K.E., Nkansah, M., Hutchison, I.J. new synthetic strategies. and Rogers, S.C. Nature, 1991, 353, 124. [5] He, C., Liu, P. and Griffin. A.C. KEYWORDS Macromolecules, 1998, 31, 3145-3147. Auxetic, negative Poisson’s ratio, monofilament, [6] Yeganeh-Haeri, Y., Weidner, D.J. and wrapped yarn, fabrics. Parise J.B. Science, 1992, 257, 650-652. [7] Peura, M.; Grotkopp, I.; Lemke, H.; REFERENCES Vikkula, A.; Laine, J.; Müller, M.; and Serimaa, R. [1] Evans KE. and Alderson A. Adv. Mater. Biomacromolecules, 2006, 7, 1521-1528 2000, 12(9), 617-624. [8] Nakamura, K.; Wada, M.; Kuga, S. and [2] Alderson, K.L., Alderson, A., Smart, G., Okano, T. Journal of Polymer Science Part B: Simkins, V.R. and Davies, P.J.: , Rubbers and Polymer Physics, 2004, Vol.42, No.7, 1206-1211. Composites, 2002, 31(8), 344-349. [3] Miller W., Hook P.B., Smith C.W., Wang X., Evans K.E. Comp Sci Tech 2009, 69, 651–655.

Preparation and Characterization of Multilayer Polymer Nanofibers by Multiaxial Electrospinning

Wenwen Liu, D. Bruce Chase, John F. Rabolt Department of Materials Science and Engineering, , Newark, Delaware, 19716 [email protected]

ABSTRACT results are shown in the photographs depicted in A biodegradable, multi-layer nanofiber has Fig. 3. In Fig. 3 (upper) is shown a coaxial 1 been successfully developed by using a self- electrospun PMMA/silicone oil sample that has designed and fabricated triaxial electrospinning been soaked in n-hexane to remove the silicone setup with gelatin as the sheath and core layers, oil. The results clearly show a 5µ diameter and poly (ε-caprolactone) (PCL) as the middle hollow fiber with a 1µ outer sheath. When a layer. The triaxial structure was investigated by third component (PAN) is introduced using the confocal fluorescence microscopy (CFM), FT- triaxial electrospinning setup shown in Fig. 2 IR spectroscopy and focused ion beam field and the silicone oil is removed, a larger emission scanning electron microscopy (FIB- diameter (6.0-6.5µ) fiber is observed with a FESEM). The ability to fabricate the multi- smaller diameter (1.5µ) inner fiber, presumably layered nanofibers efficiently with different (but unverified) composed of PAN (Fig. 3 biodegradable polymers will enable this triaxal lower). electrospinning technique to have wider applications in biomaterials and tissue engineering constructs.

INTRODUCTION Our research in multiaxial electrospinning was motivated by the fact that in coaxial electrospinning of miscible (or moderately miscible) polymer solutions, mixing can occur at the syringe tip producing a compound fiber as opposed to a stratified layer core/shell fiber. The introduction2 of an interfacial liquid can be used to keep the two miscible (or moderately miscible) layers from mixing. In addition when polymers are combined with inorganic precursors, many new applications of Figure 1. Schematic of a coaxial syringe that we have used to produce silicone oil/PMMA core/shell multifunctional nanofibers including sound fibers shown in Fig. 3 (upper). adsorption, targeted drug delivery and solar energy applications can be envisioned. Shown in Fig. 1 is a schematic of the coaxial electrospinning device we have used to produce hollow-core fibers as a way to perfect a strategy for developing our triaxial electrospinning system. Although it follows a common design, it has the flexibility to add a third component by the insertion of another polymer syringe (Fig. 2 ). Preliminary FE-SEM

Figure 2. Actual triaxial syringe that we have used to produce PMMA/silicone oil/PAN fibers shown in Fig. 3 (lower). The fibers were soaked in n-hexane to remove silicone oil from intermediate layer leaving the PMMA sheath and the PAN core.

Figure 3. FE-SEM photographs of PMMA/silicone oil coaxial spun fiber (top) and triaxial electrospun PMMA/silicone oil/PAN fiber (bottom). In both cases the silicone oil was removed post spinning.

Based on these preliminary experiments we have continued to electrospin coaxial and triaxial fibers and the results will be discussed in detail for gelatin/PCL/gelatin triaxial electrospun polymer nanofibers1.

REFERENCES 1. Liu, W.; Chase, B.; Rabolt, J. F., ACS Macro Letters (submitted) 2. Kurban, Z.; Lovell, A.; Bennington, S. M.; Jenkins, D. W. K.; Ryan, K. R.; Jones, M. O.; Skipper, N. T.; David, W. I. F., Journal of Physical Chemistry C 2010, 114 (49), 21201- 21213.

Carbon Fibers and Composites

Use of Raman Spectroscopy to Resolve Analysis of Structure of Graphene-Coated Fibers Ian R. Hardin and Susan Wilson University of Georgia, Athens, Georgia [email protected]

INTRODUCTION. Graphene is a one method similar to that described by Cui et al [7] atom-thick material made up of sp2-bonded to coat cotton fibers with carbon nanotubes. The carbon atoms. It is effectively one layer of the isolated dispersions of exfoliated graphene structure of graphite. Its unique properties sheets were first examined. They were pipetted include high onto a mica sheet and dried. These sheets were electrical and then imaged with atomic force microscopy thermal (AFM) The fluorescence spectrum of the

conductivity, the graphite dispersion in Py-SO3 was monitored quantum Hall using a fluorescence spectrophotometry. The effect, massless morphology, microstructures and EDX analysis transportation of the graphene-coated pyrolytic carbon were Figure 1: Graphite characterized using scanning electron micro properties, and strong mechanical properties -scopy. Electrochemical charge/discharge [1-5]. Cotton fabric was treated with performance of the graphene-coated pyrolytic graphene/pyrene-derivative suspensions and carbon was evaluated using button coin cells annealed at 700 degrees in a furnace under argon assembled in a high purity argon filled glove box. flow. Although initial results showing high Charge (lithium insertion) and discharge (lithium capacitance properties indicated creation of a extraction) were conducted. Raman spectroscopy graphene film on the surface of the fibers, other was used to monitor D,G and G’ shift bands for results seemed to contradict this. Raman creation of graphene on the surfaces, and to spectroscopy is used to determine the presence measure numbers of layers created.Elemental of graphene and the number of layers created analysis by EDAX was used to monitor progress under varying treatments. in annealing.

APPROACH. A graphene suspension was RESULTS. Atomic force microscopy (AFM) synthesized from natural graphite flakes by a showed that the size of the graphene patches method similar to that described by He et al[6]. were in the micrometer range. Variation in the The exfoliation process was monitored by thicknesses were analyzed and attributed to the monitoring the fluorescence ultraviolet-visible possible inhomogeneous coverage of Py-SO3 absorption spectrum at the beginning and end of molecules on the graphene surface. SEM images the exfoliation period. The obtained grey of the graphene-coated pyrolytic carbon after suspension was used directly to prepare a annealing showed how the graphene sheets grew graphene coated textile by annealing. up on the fibers with the fibers keeping the original morphological structure. This indicates Graphene-coated pyrolytic carbon. Graphene that pyrene molecules are successful in sheets were produced on cotton fabric by using a “glueing” the graphene sheets to form a

membrane on the surface of the fibers during increased capacity and cycle life, and to improve annealing. EDAX data indicated that almost 100 the formation and performance of the percent of the elements are on the surface of the graphene-coated pyrolytic carbon. observed fibers are carbon, which means that the oxygen containing groups in the graphene sheet REFERENCES and the Py-SO3 have almost completely 1. K.S. Novoselov, A.K. Geim, S.V. Morozov, disappeared. This further demonstrates that the D. Jiang, Y. Zhang, S.V. Dubonos, I.V. graphene sheets are formed the fusion of Grigorieva, and A.A. Firsov. Science, 2004, graphene sheets and Py-SO3 on the fiber 306. surfaces. 2. Y. B. Zhang, Y. W. Tan, H. L. Stormer and P. Kim, Nature, 2005, 438, 201. CAPACITANCE MEASUREMENTS. 3. K. S. Novoselov, Nature, 2005, 438, 197. Galvanostatic charge-discharge experiments 4. Y. Hernandez and V. Nicolosi, Nature were carried out at a current density of 50 mA Nanotech., 2008, 3, 563. g-1 within a voltage window of 0.01–2.8 V. 5. S.S Li, K.H Tu, C.C. Lin, C.W. Chen and These showed that graphene-coated pyrolytic M. Chhowalla. ACS Nano, 2010 4 ,3169, carbon probably has larger lithium storage 6. M. Zhang, R. Parajuli, W. Cheung, R. capacities than graphene paper anodes normally Brukh, H. X. He, Small, 2010, 6, 1100. used in lithium batteries. For the graphene 7. H.l. Wang, L.F. Cui, Y. Yang, H. S. coated pyrolytic carbon anodes, about 50 percent Casalongue, J.T. Robinson, Y. Liang, Y. of capacity loss was observed in the first cycle, Cui, and H.J. Dai. J. Am. Chem. Soc., 2010, We believe that the high electro-chemical 132, 13978. performance of the graphene-coated pyrolytic carbon is due to the porous graphene sheets and the high surface area of pyrolytic carbon. The annealing process dramatically reduced gaps between individual graphene sheets and also improved the electrical contacts between graphene sheets around the fibers. At the same time, the porous structure of graphene allows the lithium ion to penetrate into pyrolytic carbon. Figure 2: EDAX after annealing

CONCLUSION. Graphene-coated pyrolytic 250 ) carbon materials were created by fusing -1 200

graphene sheet by annealing onto cotton fibers, mAh g

( thus creating graphene-coated cotton, or 150 graphene/cotton composites.The graphene 100 -coated pyrolytic carbon materials and their 50 excellent electrical properties suggest many Discharge capacity 0 potential applications, especially as anodes in 0 1020304050 lithium batteries. This work is continuing. The Cycle number potentially low-cost method could have much Figure 3: Cycle performance broader applications. Further study is ongoing to determine the exact mechanism for this

Carbon Fiber from Extracted Commercial Softwood Lignin

D. A. Baker, D. P. Harper, and T. G. Rials Center for Renewable Carbon, The University of Tennessee, Knoxville, TN 37996-4570 [email protected]

INTRODUCTION manufacture, two extraction methods were used; the The manufacture of carbon fiber from lignin has first to evaluate the effect of a series of solvents been the subject of much recent study. Generally, the (lignins AP to AR) and the second to simplify the lignin preparations used were impure and either had sequential solvent extraction method (lignins BP to low glass transition temperatures or high BR) for comparison (Figure 1). polydispersity that likely contribute to low carbon fiber mechanical properties (0.2 to 0.6GPa strength) and long manufacturing times (1 day to 3 weeks)1,2. To manufacture a carbon fiber from lignin, the lignin first requires melt spinning to produce fiber. The fiber is then oxidatively thermostabilized to render it infusible so that carbonization can proceed. The integrity of the fiber during oxidative Figure 1: Extraction series for SWL stabilization depends on its ability to crosslink, so that the glass transition (Tg) of the material is The first series of lignin samples were recovered maintained above the processing temperature, as follows. SWL was purified (AP) and then ultimately rendering it infusible. Lignin, which is sequentially solvent extracted at room temperature, naturally partially oxidized, demands critical control by the action of four differing solvents. AP was first of the melt-spinning step and has to be prepared to extracted with Solvent 1 until minimal further lignin have a low enough melt flow temperature (Tmf ) for it could be removed. The extract was evaporated to to be melt spun without polymerizing during give A1 and the residual solid recovered. This solid extrusion, and a high enough Tg for stabilization to was extracted with Solvent 2 and the extract proceed at an acceptable rate. Thus a narrow thermal evaporated to give A2, the residual solid was used in window of opportunity exists for efficiently the next extraction and so on until A1-A4 were manufacturing carbon fiber from lignin. Should these recovered and some residual lignin (AR) remained. obstacles be overcome without much additional cost The second series of lignin samples (BP, B3, B4 to the lignin precursor, it offers several advantages: it and BR were recovered in a similar manner but only is relatively inexpensive, renewable, and it can be used Solvent 3 & Solvent 4 in the extractions. potentially be oxidatively thermostabilized at much Lignin samples (SWL, AP & A1-A4; BP, B3 & higher rates than either polyacrylonitrile or B4) were examined for their elemental composition mesophase pitch. This allows for substantial cost (CHNS), ash contents, carbohydrate contents, reduction in carbon fiber manufacture. infrared spectra, syringyl/guaiacyl lignin monomer The best lignin-based carbon fibers produced contents, Tg properties, melt flow (Tmf), basic carbon have strengths of 185KSI (1.28 GPa)3 and are yield and oxidative thermostabilization properties. projected to cost much less than other known To determine which lignins would be selected methods of carbon fiber production. Efforts to further for larger scale manufacture (~2Kg) and pilot scale increase strength have been historically restricted by melt spinning, an assessment of some of the lignin the unavailability of suitable lignins. Therefore the preparations melt spinning capabilities were objective of this work was to first purify and then performed using a Haake bench-top twin screw manipulate the molecular weights of several extruder. In some cases, this determination was made commercial lignins to give precursors that are most by drawing fiber directly from molten lignin. suitable for carbon fiber production.

RESULTS AND DISCUSSION EXPERIMENTAL Several lignin samples were obtained using the To investigate the possibility of using solvent purification and sequential solvent extraction fractionation to provide pure softwood kraft lignins methods. In each case, the SWL purification yields (derived from SWL; Indulin AT, MeadWestvaco) of were 91.2% and 90.4%, respectively, for AP & BP. It suitable glass transition (Tg) for carbon fiber was found that while SWL contained 2.73% ash and

some carbohydrate impurities, the purified lignins 0.1°C/min and samples A4 & B4 could be stabilized both contained 0.78% ash and no carbohydrates. The under all test conditions. These data were in solvent extracted lignins (A1 to A4, B3 & B4) also agreement with the measured Tg’s for the samples. contained no carbohydrates and had even lower ash contents varying from 0.39 to 0.70%. The residual Table 2: TGA observations for each lignin. (s, insoluble lignins (AR & BR), comprising around stabilized; sf, slight fusion; f, fused; m, melted). 12% of the lignin (relative to AP or BP), contained much ash suggesting that whatever ash remained in Oxidative thermostabilization rate (°C/min) 0.1 0.2 0.5 1 2 5 10 20 the purified lignins was effectively concentrated in Lignin the residue due to solvent extraction. Thermal ramp time (min) The first two solvent extractions in sequence A 1500 750 300 150 75 30 15 7.5 gave yields of less than 1% and therefore were not AP ~ sssf f f m ~ used in extraction series B, as it was determined that A1 m m ~ ~ ~ ~ ~ ~ the small amount of these lignins (A1 & A2) that A2 f m ~ ~ ~ ~ ~ ~ would be present in extracts B3 and B4 would not be A3 sf m ~ ~ ~ ~ ~ ~ detrimental to lignin properties and would simplify A4 ssssssss scale-up. The yields of A3, A4, B3 and B4 were BP ~ sssf f f m ~ 58.1%, 27.3%, 53.3% and 34.7% respectively. B3 sf m ~ ~ ~ ~ ~ ~ Differential scanning calorimetry and Fisher- B4 ssssssssf

Johns measurements (Table 1) showed that each further extraction gave an increased Tg lignin and that Simple fiber formation experiments suggested potentially all of them, with the exception of the that samples A1-A4, B3 and B4 could potentially be parent lignin (SWL) and the purified lignins (AP and melt spun on suitable pitch fiber spinning equipment.

BP) could possibly be melt spun and converted to carbon fiber. (These exceptions are due to the CONCLUSIONS AND FUTURE WORK presence of infusible materials and/or contaminants A sequential solvent extraction process has been which would cause problems with melt spinning and developed that produces lignin fractions with subsequent flaws in the carbon fibers). predictable, and desirable, thermal characteristics. In summary, these data have shown that the most Table 1: Tg and melt data for lignins (* denotes an promising candidates for carbon fiber production incomplete melt). were A3, A4, B3 and B4 so that while they can be melt spun, oxidative thermostabilization will proceed Lignin Tg (°C) Tmf (°C) Flow (°C) at an acceptable rate. However, A3 and A4 were SWL 152 184* 199 similar to B3 and B4, respectfully, and therefore AP 156 189* 196 several lignin samples have been prepared on the A1 66 73 80 2Kg scale to mimic B3 and B4. In addition to this a A2 113 128 142 third series was also obtained (i.e. CP, C4 & CR) A3 131 153 164 whereby only Solvent 4 was used to extract CP so A4 200 226 240 that a lignin with intermediate Tg was obtained. BP 156 197* 210 Furthermore, similar experiments have been B3 129 151 164 performed using other parent lignins such as a hardwood kraft lignin (HWL, PC1369, Mead B4 193 227 242 Westvaco) and an organosolv lignin (OSL, Alcell, Lignol Innovations) where it was found that Solvents Thermogravimetric analysis was used to 1 and 2 give rise to moderate yields of lignins. simulate oxidative thermostabilization and carbonization. 10 mg of each lignin, excepting SWL, were aerobically treated to 250°C at a rate of 0.1, 0.2, REFERENCES 0.5, 1.0, 2.0, 5.0, 10 or 20°C/min and held [1] Kadla JF et al. (2002); “Lignin-based carbon isothermally for 30 minutes to potentially cause fibers for composite fiber applications.” Carbon 40 stabilization. Each was then carbonized by heating to (15):2913-2920. 950°C at a rate of 10°C/min under an inert [2] Baker,D.A. et al. (2012); “On the characterization atmosphere. The condition of the sample was and spinning of an organic purified lignin towards the recorded after each test. It was found (Table 2) that manufacture of low-cost carbon fiber.”, J. Appl. the purified lignins, AP & BP, could be thermally Polym. Sci., 124, 227-234. stabilized at rates lower than 1.0°C/min, A1 & A2 [3] Baker, D.A. et al.; “The rapid manufacture of could not be stabilized under any of the tests, A3 and high-strength lignin-based carbon fibers.” ACS B3 could possibly be stabilized at rates lower than National Meeting, Anaheim, CA, March 27-31, 2011.

Electrospun Carbon Nanofibers from Kraft Lignin

Omid Hosseinaei and Darren A. Baker Center for Renewable Carbon, University of Tennessee, 2506 Jacob Dr., Knoxville, TN, USA [email protected]; [email protected]

INTRODUCTION mixture of two solvents optimized for lignin dissolution Study of the conversion of biomass into fuels, chemicals and evaporation during fiber formation. The lignin and other value-added materials is increasing rapidly for solution was placed in a 5 mL plastic syringe mounted on the replacement of petroleum-based products towards cost a syringe pump, and a potential difference was applied to reduction and global sustainability. Among biomass it via a needle mounted on the syringe. A rotating polymers, lignin is the second most abundant behind grounded cylinder (diameter, 3”; width, 4”) was used as cellulose and is about 16-35% dry mass of biomass. The collector. Parameters such as polymer concentration, flow paper industry is currently the main producer of lignin as rate, electrical field strength and distance between tip and a by-product of pulping processes. Different pulping collector were optimized for this particular lignin. processes are used for producing pulp with differing Oxidative thermostabilization of the spun fiber mats, properties, of which the kraft process is dominant. The to render the lignin infusible, were performed by heating lignin by-product is used mainly as an energy source and the sample to 250°C under air flow (0.07 m3/min) at a rate has therefore been assigned a low value. Low-cost carbon of 0.1 to 20°C/min using a forced air programmable fibers are one of the potential value-added materials convection furnace. Each oxidatively thermostabilized which can be manufactured using lignin (Uraki et al. fiber mat was then carbonized in a tube by heating to 1995; Kadla et al. 2002; Baker et al. 2012). Impurities, 950°C at a rate of 10°C/min under inert conditions. low molecular weight and glass transition temperatures The yields of thermostabilization and carbonization are factors which negatively affect carbon fiber steps were calculated. Morphology of the fiber mats were production from lignin, which need to be addressed studied by scanning electron microscopy (SEM), while before commercialization is possible. chemical and thermal properties of lignin fibers and However, aside from carbon fiber, much recent work thermostabilized fibers were examined by infrared has been performed in the manufacture of carbon spectroscopy and thermogravimetric analysis (TGA). nanofiber mats via electrospinning. Electrospun carbon nanofibers have potential applications in areas such as RESULTS AND DISCUSSION filtration, energy storage and nanocomposites (Huang et The purified/extracted lignin, SWKL-E, had a lower al. 2003), and this is due to their high surface-to-volume ash content (0.58%) and higher glass transition (185.3°C; ratio and strength. Commercialization can be achieved Figure 1) compared to original lignin (2.73% & 147.5°C, provided the carbon nanofibers can be manufactured respectively) and was prepared with an overall yield of quickly and efficiently. However, previous studies on the 39.7% from SWKL; 22.9% of SWKL was removed manufacture of lignin based carbon nanofibers (Ruis- during purification, 30.6% was recovered as lower Rosas et al. 2010) have required treatment times of molecular weight lignins and 6.8% was found to be between three days and two weeks weeks for conversion infusible/insoluble. Py-GCMS showed that all of the nanofibers into carbon. carbohydrates had been removed while EA revealed that Therefore the objective of this work was to purify free sulfur contaminants had also been removed. and extract a commercial lignin product so that subsequent products manufactured from it are converted into carbon fiber quickly. We therefore used electrospinning to manufacture and characterize uniform mats of electrospun lignin nanofiber that were rapidly converted to carbon nanofiber.

MATERIALS AND METHODS A commercial softwood kraft lignin (SWKL; Indulin AT) was used to obtain a refined lignin product. SWKL was first purified to remove most impurities (carbohydrates, rosins and most ash) and sequentially solvent extracted to remove lower molecular weight components and therefore refine molecular weight distribution. The T of the lignins g produced were measured by differential scanning Figure 1. DSC curves of SWKL and SWKL-E. calorimetry (DSC; PE Pyris Diamond). CHNS contents Electrospun mats were successfully prepared from and carbohydrate impurities were monitored by elemental several lignins including SWKL-E and the best, i.e. those analysis (EA) and pyrolysis/gas chromatography/mass without flaws and with good spinnability, were selected spectrometry (Py-GC/MS), respectively. for oxidative thermostabilization and subsequent Electrospinning solutions were prepared by conversion into carbon nanofibers. dissolving the most promising lignin (SWKL-E) in a Oxidative thermostabilization is an important step in The carbon nanofibers were uniform without beads carbon fiber manufacture which prevents fusion during and without surface defects (Figure 4 a, b and c). The carbonization. Stabilization increased the thermal stability distribution of fiber diameter showed the majority of of the electrospun lignin fibers (Figure 2). The main fibers to have a diameter between 300-500 nm (Figure 4 effects of oxidative stabilization were a decrease in d). The average diameters of the fibers were 343±128 nm. intensity of bands relating to C−H stretching (Figure 3; -1 2950 and 2870 cm ) and an increase in intensity of bands (a) (b) related to carbonyl groups (1730 cm-1). This is caused by crosslinking and condensation reactions which convert the lignin to a thermoset polymer with removal of any Tg and increased thermal stability (Braun et al. 2005; Brodin et al. 2012). A lignin weight loss was also observed (24.5% & 20.8%, using rates of 0.1°C/min and 20°C/min respectively) due to these condensation and dehydration reactions during the treatment (Uraki et al. 1995). (c) (d)

Stabilized Figure 4. SEM images of electrospun carbon nanofibers (a,b and c) and frequency of fiber diameters (d). Green

CONCLUSIONS

Uniform mats of lignin-based carbon nanofiber have been

manufactured from a purified commercial SWKL by

electrospinning. Removal of contaminants and

manipulation of the lignin T allowed the conversion of Figure 2. TGA curves of green and stabilized nanofibers. g lignin-based nanofibers into oxidatively thermostabilized nanofibers and then into carbon nanofibers much more quickly (1 hour; 20°C/min to 250°C oxidative

2870 thermostabilization) than has been previously reported (3- 3400 2950 1730 14 days; 0.01 to 0.05°C/min to 250° oxidative Stabilized thermostabilization). No fusion of the fibers was observed.

REFERENCES Baker DA, Gallego NC, Baker FS (2012) On the characterization Green and spinning of an organic-purified lignin toward the manufacture of low-cost carbon fiber. Journal of Applied Polymer Science 124 (1):227-234. Braun JL, Holtman KM, Kadla JF (2005) Lignin-based carbon fibers: Oxidative thermostabilization of kraft lignin. Carbon 43 (2):385-394. Brodin I, Ernstsson M, Gellerstedt G, Sjöholm E (2012) Oxidative Figure 3. FTIR-ATR spectra of electrospun nanofibers. stabilisation of kraft lignin for carbon fibre production. Holzforschung 66 (2):141-273. The carbonization yields of the stabilized nanofibers Huang Z-M, Zhang YZ, Kotaki M, Ramakrishna S (2003) A review oxidatively stabilized at 0.1°C/min and 20°C/min to on polymer nanofibers by electrospinning and their applications in nanocomposites. Composites Science and Technology 63 250°C was 38.9% and 40.2%, respectively, and was lower (15):2223-2253. than expected. Carbonization of the sample treated at Kadla JF, Kubo S, Venditti RA, Gilbert RD, Compere AL, Griffith 0.1°C/min in a TGA gave a higher yield of 46%, and this W (2002) Lignin-based carbon fibers for composite fiber is attributed to the higher volume of the tube furnace applications. Carbon 40 (15):2913-2920. compared to the TGA furnace, which increases the Ruiz-Rosas R, Bedia J, Lallave M. et al. (2010) The production of presence of impurities in the nitrogen gas and strips submicron diameter carbon fibers by the electrospinning of lignin. Carbon 48: 696-705. carbon from the sample at elevated temperatures. This Uraki Y, Kubo S, Nigo N, Sano Y, Sasaya T (1995) Prepration of indicated that a sacrificial carbon should be added to the carbon-fiber from organosolv lignin obtained by aqueous tube furnace during further studies on small samples. active-acid pulping. Holzforschung 49 (4):343-350.

Mesoporous Activated Carbon Nanofiber Synthesis from Catalytic Graphitization of Polyacrylonitrile/Cobalt Sulfide Composite

Yakup Aykut1, Behnam Pourdeyhimi2, Saad A. Khan3 1Department of Textile Engineering, Uludağ University, Bursa, Turkey, 16059 2Fiber and Polymer Science, North Carolina State University, Raleigh, NC, USA, 27695-8301 3Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA, 27695-7905 [email protected]

INTRODUCTION RESULTS AND DICUSSION Nanotechnological developments in the past decades have Morphological evaluations of the NFs were performed helped to improve device performances by either with scanning (SEM) and transmission electron enhancing material properties or developing new microscopes (TEM), and are shown in Figures 1 and 2. As processing techniques. Synthesis of carbon based seen from the Figure 1, as-spun PAN (Fig. 1a), and pure materials on the nanoscale can increase device carbon NFs (Fig. 1b) are uniform and no porosities are performance by several orders of magnitudes. Further, seen but mesoporous structures are observed on the producing them with porous structures in the nanoscale carbon nanofibers that are produced from H2S threaded can further enhance the final device performance because PAN/CoCl2 composite. This is as a result of the activation the significant increase in total specific surface area. of carbon nanofibers and the migration of cobaltous phase Carbon nanotubes (CNTs) have been produced via in the fibers during the heat treatment processes. different techniques and used in electron emitting devices Mesoporous structure are obtained because the particles as in scanning electron microscopy (SEM), field effect move and exit from the fibers (Fig. 1c). The motion of emitters (FEEs), and field emitted displays (FEDs) cobalt particles in carbon nanofibers can be explained by because of their high electron emission properties [1]. the phase behavior of cobalt and carbon at high Electrospinning is a novel processing technique to temperatures [3]. produce 1D carbon nanofibrous system [2]. In the process, a proper stock solution is initially electrospun, then stabilized in air and finally carbonized in an inert atmosphere. In this study, we prepared mesoporous electrospun carbon nanofibers via this approach. Nanofibers were evaluated using SEM, TEM, XPS and Raman spectra.

MATERIALS AND METHODS A proportionate amount of polyacrilonitrile (PAN) and cobaltous chloride salt precursors (wt. % of CoCl respect 2 Figure 1. SEM images of electrospun a) as-spun PAN, b) to PAN in the solution) were dissolved in just carbon nanofibers, and c) carbonized NFs of H S dimethylformamide (DMF). 1ml liter of the stock solution 2 threaded PAN/CoCl composite. was loaded into a plastic syringe fitted with a stainless 2 steel needle and inserted in a syringe pump with To further understand the phenomenon, TEM controlled flow rate mechanism. The metal needle was observations of the fibers were carried out and connected to a high voltage source, and a grounded demonstrated in Figure 2. As-spun PAN NFs are almost collector was placed in front of the needle at a specificed translucent (Fig.2a) and CoCl nanoparticles are evident distance. Because an electric field is created between the 2 in PAN/CoCl NFs corresponding to the dark regions in metal needle and the grounded collector the polymer 2 Fig. 2b. Fuzzy surface represent the formation of cobalt solution is directly ejected toward the collector and the jet sulfide after soaking as-spun PAN/CoCl NFs in H S. is elongated and collected in the form of nanofibrous mat. 2 2 During the stabilization and carbonization process, the As-spun NFs were soaked in H S and held for 1 hour. NF 2 cobaltous phases migrate in the NFs and leave the fibers samples were rinsed with deionized water several times leaving mesoporous structures behind them (Figs. 1c and and then dried in vacuum hood. Mesoposous CNFs were 2d). obtained after stabilizing (in air at 280oC for 1 hr), and then carbonizing (in nitrogen atmosphere at 800oC for 2 hrs) the dried NFs.

1571 cm−1 (G-band) are detected [4]. These peaks are assigned to disordered carbons in graphene layers and ordered graphite phases. The intensity ratios R=(ID/IG) of these peaks thus indicate the nature of the structural order of the graphitic phase in the CNFs. The decrease of this ratio for mesoporous CNFs indicates that more ordered graphitic structures are obtained in the NFs.

800 (a) CNFs 700 (b) Mesoporous CNFs

600 a 500

400

Relative Intensity Intensity Relative 300

200 b 100 1000 1200 1400 1600 1800 Figure 2. TEM images of a) PAN, b)PAN/CoCl , c)H S 2 2 Raman Shift /cm-1 threaded of b, and d) carbonized of c nanofibers. Figure 4. Raman spectra of a) CNFs and b)mesoporous CNFS.

CONCLUSION Mesoporous activated mesoporous carbon nanofibers C 1s were synthesized after H2S and heat treated electrospun PAN/CoCl2 composite NFs. All nanofibers were

N 1s characterized with SEM, TEM, XPS and Raman spectroscopy. The results reveal that mesoporous CNFs were successfully produced, and the Raman spectra

O 1s indicate that mesoporous CNFs are activated and have CPS (a.u.) more graphically ordered structures. Co 2p

Co LMM O KLL N KLL ACKNOWLEDGMENT This work was supported by the Nonwoven Cooperative S 2s S 2p Co 3p Co 3s Research Center, NCSU, US and the Ministry of National Education, Republic of Turkey. 0 200 400 600 800 1000 1200

Binding Energy (eV) REFERENCES Figure 3. XPS of polyacrylonitrile/cobalt sulfide [1]. J.M. Bonard, J.P. Salvetat, T. Stockli, et al., Appl. composite nanofibers. Phys. Lett., 1998, 73, 918-920. [2]. F. Ko, Y. Gogotsi, A. Ali, et al., Adv. Mater., 2003, 15, 1161-1165. The dried H2S treated PAN/CoCl2 NFs were analyzed with XPS to examine the elemental composition of the [3]. J. Li, X. Yi, H. Ye, Carbon, 2010, 48, 4574-4577 NFs (Figure 3). All peaks representative of the formation [4]. Y. Aykut, ACS Appl. Mater. Interfaces, 2012, 4, 3405-3415. of cobalt sulfide are observed on the fibers after H2S treatment.

In order to determine the graphitic structures of the carbonized NFs, Raman spectra of the NFs were conducted and shown in Figure 4. As seen from the spectra, two distinct peaks at ca. 1329 cm−1 (D-band) and

Electrically Conductive Fibers with Carbon Nanotubes: 3D Analysis of Conductive Networks by Electron Tomography

Wilhelm Steinmann1, Johannes Wulfhorst1, Thomas Vad1, Gunnar Seide1, Thomas Gries1, Markus Heidelmann2, Thomas Weirich2 1Institut für Texiltechnik (ITA) der RWTH Aachen University 2Gemeinschaftslabor für Elektronenmikroskopie (GFE), RWTH Aachen University [email protected]

INTRODUCTION resulting in a melt draw ratio MDR between 1.0 and 25. For the production of electrically conductive fibres, The maximum MDR depends on the CNT concentration several approaches exist. One of them is to use polymer and reaches values of 25 (0 w% CNT), 15 (3.5 w% CNT), nanocomposites. Nanoparticles like carbon nanotubes 7 (6 w % CNT) and 6 (10 w% CNT). (CNT) have a good performance in electrical and thermal conductivity as well as mechanical properties [1]. Several Draw winding authors have proved the enhancement of the electrical Fibers are drawn in solid state on a fiber spin line from conductivity of insulating polymers with the help of DSM XPlore, Geleen, Netherlands, where the fibers are carbon nanotubes. The electrical conductivity can be drawn between two godets. Between the godets, a heated described by percolation models and mainly depends on chamber oven is placed with a temperature of 120 °C. the amount of particles as well as the particle geometry Draw ratio DR is varied between 1.1 and 4.1. [2]. For carbon nanotubes with high aspect ratios, low amounts are sufficient for achieving electrical Characterization conductivity. Electrically conductive fibers based on Electrical conductivity of the samples (extruded strings nanocomposites have so far been only realized in slowly and fibers) is measured by an LCR meter as a function of spun monofilaments [3,4]. Another possibility in the AC frequency. The values indicated in the diagrams coating of insulating materials with an intrinsically represent the DC conductivity which is measured at the conducting polymer (ICP) like PEDOT:PSS [5]. Today, lowest frequency (12 Hz). mostly silver coated polyamide fibres are used for textile For analyzing the nanostructure, electron tomography is applications. All of these approaches provide no electrical used. Fiber and granule samples are cut into thin slices of insulation, making impossible their use in moist 100 nm with an ultramicrotome from Zeiss AG, Jena, environments. Furthermore, the electrical conductivity of Germany. In the electron microscope, the sample is tilted the coated fibres is reduced by washing them. The and bright field images are recorded at different tilting washability is no problem for nanocomposite fibres, since angles, allowing a 3D reconstruction of CNT in the the particles are incorporated in the fibre volume. polymer. The experimental setup is shown in figure 1.

EXPERIMENTAL Compounding Multiwalled carbon nanotubes (CNT NC7000) from Nanocyl s.a., Sembreville, Belgium, are compounded into four different polymers, which are polypropylene (PP), low density (LDPE), polyamide 6 (PA6) and ethylene vinylacetate (EVA) using a KETSE 2040 twin screw compounder from Brabender GmbH, Duisburg, Germany. CNT concentration is controlled by two dosage systems, whereas mass throughput is controlled by the screw rotation speed and set up 1 kg/h. Concentration of CNT is varied between 1 % and 20 %. After compounding, the material cut into granules. Figure 1: Experimental setup for electron tomography Melt Spinning Melt spinning is carried out on a microcompounder from RESULTS AND DISCUSSION DSM XPlore, Geleen, Netherlands with an attached Percolation threshold winding unit from the same company. The machine is With the help of extruded strings, percolation threshold is used in batch mode and the material is mixed for 5 determined from the specific resistivity. It is the point in minutes. For the spinning process, a die diameter of 0.5 the diagram (see figure 2), where resistivity drastically mm is used and mass throughput is controlled by the decreases. screw rotation speed, which is varied between 5 and 20 rpm. Winding speed is varied between 20 and 200 m/min, Influence of process parameters during spinning S 1,00E+05 LDPE ρ In the melt spinning process, specific resistivity increases 1,00E+04 PP as a function of melt draw ratio MDR. The relative 1,00E+03 PA6 increase of resistivity is higher for low CNT EVA ·cm] 1,00E+02 concentrations (see figure 4). During spinning, CNT Ω

[ networks are deformed to longer fibrils and for lower 1,00E+01 concentration, conductive fibrils partially don’t touch 1,00E+00 each other when drawn too much.

Specific resistivity resistivity Specific 1,00E-01 25 0 2,5 5 7,5 10 12,5 15 17,5 20 10 w% CNT 20 CNT concentration xc [w%] [-] 6 w% CNT

δ Figure 2: Specific resistivity as a function of CNT 15 concentration for four different polymers 10 The results for the different polymers are summarized in

resistivity 5 table 1. It is obvious, that PP has the lowest percolation threshold and is therefore used for further spinning trials. increase Relative of 0

Table I: Values for percolation threshold (PT) and 1,0 2,0 3,0 4,0 5,0 6,0 7,0 Melt draw ratio MDR [-] maximum conductivity (MC) with a loading of Figure 4: Relative increase of specific resistivity as a 20 w% for the different polymers Polymer PP LDPE PA6 EVA function of melt draw ratio for different CNT PT [w%] 3 6 5 7 concentrations in polypropylene

MC [S/cm] 3.78 1.45 1.67 0.95 CONCLUSION

The study reveals that compounding, melt spinning and The reason for differences in the percolation threshold can solid state drawing all have an important influence on the be found in the nanostructure. In PP, CNT are connected production of electrically conductive polymeric fibers. to networks, whereas in the other polymers CNT are Polypropylene is the most suitable matrix material for separated and higher amounts of nanoparticles are needed these fibers, since conductive networks are formed. to let them touch each other. The differences are During spinning and drawing, conductivity decreases displayed in figure 3 for PP and PA6. since conductive networks are oriented or CNT are pulled out of the networks. Furthermore, electron tomography is a good method for detecting the changes at the nanoscale.

OUTLOOK TO FUTURE WORK For the application of electrically conductive polymeric fibers in smart textiles, conductivity is still low. Figure 3: Transmission electron microscopy image of Therefore, it is necessary to increases these values, CNT distribution in polypropylene (left) and whereas heatsetting of the fibers is a possibility for polyamide 6 (right) restoring the electrical properties after compounding.

Influence of solid state drawing Furthermore, conductive plasticizers may be added to the During solid state drawing, electrical conductivity material to increase spinability and also conductivity. decreases with increasing draw ratio (see figure 5). REFERENCES 40 [1] Thostenson E.T. et al., “Elastic properties of carbon nanotube-based composites: modeling and characterization”, J Phys D 36, 2003, pp. 573. 30 [2] Logakis E. et al. “Low electrical percolation threshold in

·cm] 20 poly(ethylene terephthalate)/multi-walled carbon nanotube

Ω nanocomposites”, Eur Polym J 46, 2010, pp.928. 10

S [ [3] Deng, H. et al. “Preparation of High-Performance Conductive ρ 0 Polymer Fibers through Morphological Control of Networks Formed byNanofillers“, Advanced Functional Materials 20, 2010, pp. 1424. Specific resistivity Specific 11,522,533,544,5 [4] Steinmann W, Walter S, Seide G, Gries T (2011) Melt spinning of Draw ratio DR [-] electrically conductive bicomponent fibers. In: Adolphe D, Schacher L, editors: 11th World Textile Conference AUTEX 2011, 8-10 June 2011, Figure 5: Specific resistivity as a function of solid state Mulhouse, France. Book of Proceedings, Volume 2. Mulhouse : Ecole draw ratio for polypropylene Nationale Supérieure d'Ingenieurs Sud-Alsace. pp. 716-721. [5] Skrifvars, M., Bashir, T., Persson, N.K., „Preparation of Conductive The reason for the increase in specific resistivity is a Viscose Fibres by Vapour Deposition Polymerisation of Polythiophene“, partial destroying of the CNT networks. Single CNT are 49th Dornbirn Man-Made Fibers Congress, Austria, 2010. pulled out of the conductive networks with increasing draw ratio and don’t contribute to conductivity anaymore.

Clean Water / Clean Energy

Electrospun Nanofiber Derived TiO2 Active Layer for Dye-Sensitized Solar Cell Applications

Xueyang Liu1, Jian Fang1, Mei Gao2, Tong Lin1 1Institute for Frontier Materials, Deakin University, Geelong, VIC 3216, Australia, 2CSIRO Materials Science and Engineering, Clayton, VIC 3169, Australia [email protected]; [email protected]

INTRODUCTION RESULTS AND DISCUSSION Dye-sensitized solar cells (DSSCs) have attracted enormous interest in both academic and industrial areas because of the low cost, easy fabrication, versatile structure and reasonable conversion efficiency. The active TiO2 layer in DSSC has been reported to play a key role in determining solar cell performances. Among all TiO2 electrode materials, nanofibrous TiO2 is expected to have excellent photovoltaic performance because of the one- dimensional feature can optimize the transport of 1 photoelectrons . However, DSSCs made of TiO2 nanofiber working electrodes showed even lower cell efficiency compared to that from conventional TiO2 nanoparticles 2,3. This was attributed to the reduced specific surface area and low charge transport efficiency.

In our recent study, we found that when short TiO2 nanorods (NRs) were grown on TiO2 nanofibers (NFs), the hierarchical NRs-on-a-NF TiO2 showed improved solar cell performance when they were used as working electrode. In this paper, we report on the preparation of FIGURE 1. SEM images of (a) as-electrospun TiO2/PVP nanofibers, (b) the TiO2 nanofibrous structure and its photovoltaic TiO2 nanofibers, (c) hydrothermally-formed nanorods on nanofibers (d) properties. XRD patterns. (e) SEM image of the nanorods grinded from hierarchical TiO2. (f) TEM image of a single nanorod and selected area electron EXPERIMENT diffraction pattern (SAED) (insert)

TiO nanofibers were prepared by electrospinning 2 Figure 1a~c show the scanning electron microscope titanium butoxide (TNB)/polyvinylpyrrolidone (PVP) (SEM) images of different nanofibers. The as-electrospun solution in a mixed solvent of ethanol/acetic acid (v/v, TiO /PVP nanofibers have a uniform fibrous structure 8/2) followed by a calcination treatment at 500 °C to 2 with a smooth surface (Figure 1a). After calcination, the remove all the organic components. nanofibers looked rougher (Figure 1b). The calcination

led to shrinking of the fibers, from 125 nm to 83 nm in TiO nanorods were grown on the TiO nanofibers using a 2 2 diameter. When the TiO nanofibers were subjected to a hydrothermal method. 0.05g TiO nanofibers were added 2 2 hydrothermal treatment, lots of needle like crystal was to an aqueous TNB solution containing 1:1 hydrochloride grown on the TiO nanofiber surface (Figure 1c). The X- acid (35%) and water. The hydrothermal reaction was 2 ray diffraction (XRD) measurement indicated that the carried out in a sealed Teflon vessel at 150 °C for 4 hours. calcinated nanofibers were almost in a pure rutile state

(Figure 1d). These tiny nanorods looked uniform (Figure To prepare the DSSC devices, a slurry paste containing 1e). Further XRD test confirmed that the nanorods 0.5g TiO nanofibers or nanorods, 0.1 ml acetic acid, 3 ml 2 contained both anatase and rutile crystal phases. The ethanol, 1.5g terpionel and 0.25g ethyl cellulose was transmission electron microscopy (TEM) image and the coated onto a FTO glass by the doctor-blade technique. SAED pattern in Figure 1f confirmed that the TiO The coated FTO was then dried and heated at 500°C for 2 nanorods were all single crystals. 30 min. After immersing in a 0.3 mM N719 dye solution, the TiO2/FTO electrode was used to make DSSC devices. TABLE Ӏ. Physical properties of TiO2 nanorods or nanofibers I ¯/I3¯ in 3-methoxyproprionitrile was used as the A.V.G Grain size Rutile Surface area TiO electrolyte. 2 (nm) phase (%) (m²/g) NR 1 (0.85% TNB) W-19.2, L-217.4 29.8 29.84 ± 0.64 NR 2 (1.7% TNB) W-36.5, L-282.2 56.0 37.63 ± 0.33 NR 3 (3.4% TNB) W-54.6, L-317.6 72.8 32.19 ± 0.23 NR 4 (5.1% TNB) W-86.9, L-377.7 88.0 27.14 ± 0.33 NF W-15.6, L-15.6 0 22.29 ± 0.37 (W-width, L-length) photos to current of TiO2 nanorod and nanofiber By adjusting the TNB concentration in the hydrothermal electrodes. The nanorod electrode exhibited a maximum solution, the TiO2 nanorods can be easily controlled in IPCE value of 48% at 520 nm. The IPCE value at the morphology and crystal phases. As listed in Table I, with same wavelength for the nanofiber electrode was 39% the increase in the TNB concentration, nanorods size (Figure 3a). Nanofiber electrode showed different UV- increased. When the TNB concentration was increased VIS spectra to nanorod electrode, as shown in in Figure from 0.85% to 5.1%, the width and length of the nanorods 3b. Higher absorption rate means more dye molecules can increased by 350% and 74%, respectively. Because these be absorbed on the nanorods than nanofibers. nanorods were all single crystals, so the average crystal size of the nanorods was much bigger than that of the nanocrystals in TiO2 nanofibers.

Higher concentration of TNB favored the formation of rutile crystal phase in the TiO2 nanorods. With increasing the TNB concentration, the content of the rutile crystal phase increased from only 29.8% to nearly 88%.

FIGURE 4. EIS spectra of the DSSCs. (a) Nyquist and (b) Bode phase B.E.T. technique was applied to measure the surface area. plots The surface area of the nanorods increased initially when the TNB concentration increased from 0.85% to 1.7% and Electrochemical impedance spectroscopy (EIS) spectra of then reached the maximum value, 37.63±0.33 m2/g. the DSSC devices are shown in Figure 4, which provide Further increasing the TNB concentration led to decrease the information of the electron transport properties of the of the surface area. solar cells. The Nyquist plot shows the charge transfer resistance at the TiO2/dye/electrolyte interfaces. The smaller semicircle for the DSSC made of nanorod Solar J V η sc ac cells 2 (%) electrode suggested smaller electrical resistance of (mA/cm ) (V) NR 1 7.77 720.0 3.25 nanorod electrode than nanofiber one. NR 2 9.26 700.0 4.21 NR 3 10.68 685.0 4.69 The electron lifetime of the cells can be calculated from NR 4 8.82 680.0 3.66 the Bode phase plots using the equation τ=1/2πfc, where fc NF 6.71 735.0 3.13 represents the peak frequency. The lifetime for the nanorod electrode was calculated as 52 ms, which was FIGURE 2. Photovoltaic properties of the DSSCs using different TiO2 nanorods (NR 1, NR 2, NR 3 and NR 4) and nanofibers (NF) much higher than that of the nanofiber electrode (14 ms), indicating better opportunity for the photoelectrons on Figure 2 shows the photovoltaic properties of the solar nanorod electrode to be transported before they are re- cells. As shown in the current density (J)-photovoltage combined. (V) curves, all cells were similar in the open circuit voltage, around 0.7 V, but they varied in the short circuit CONCLUSIONS current. The device made of TiO2 nanofibers had the In this study, a novel nanorod on nanofiber TiO2 was lowest short-circuit density of 6.71mA/cm2. For the prepared by a combination of electrospinning, high devices made of nanorods, they showed higher short- temperature calcination and hydrothermal treatment. circuit current density compared to the nanofiber device. Compared with the conventional TiO2 nanofibers, the 2 The highest circuit current density (10.68mA/cm ) was TiO2 nanorods have higher surface area, larger crystal size found on the device using the nanorods prepared at a TNB and better photovoltaic performance. concentration of 3.4% during the hydrothermal treatment. The highest conversion efficiency of the DSSCs was KEYWORDS 4.69%. Hierarchical nanofibers, electrospinning, hydrothermal treatment, TiO2, dye-sensitized solar cells

REFERENCES 1 Greiner, A. & Wendroff, J. H. Electrospinning: A Fascinating Method for the Preparation of Ultrathin Fibers. ChemInform 38 (2007). 2 Song, M. Y., Kim, D. K., Ihn, K. J., Jo, S. M. & Kim, D. Y. Electrospun TiO2 electrodes for dye-sensitized solar cells. FIGURE 3. (a) IPCE curves and (b) UV-VIS absorption spectra of the Nanotechnology 15, 1861-1865 (2004). DSSCs 3 Onozuka, K. et al. Electrospinning processed nanofibrous TiO2 membranes for photovoltaic applications.

The incident photo to current conversion efficiency Nanotechnology 17, 1026-1031 (2006). (IPCE) was measured to compare the ability of converting

Photovoltaic Fiber Having Polymer Anode and Inverted Layer Sequence

İ. Borazan1, A.Bedeloğlu2, A. Demir1 1Istanbul Technical University, Textile Technologies and Design Faculty, 34437, Istanbul 2Dokuz Eylül University, Textile Engineering Department, 35160, Buca, Izmir [email protected]

ABSTRACT such devices electrons, which in the conventional In this study, photovoltaic fiber was developed forward mode are transported to the reflective using organic solar cell materials and inverted layer electrode, are instead extracted to the transparent sequence. Light absorbing nano-materials were electrode. This reversal of normal behavior is deposited as photoactive layer on metal and buffer generally achieved by coating the electrodes with layer coated thin and flexible fiber. While light was an inorganic or surface-functionalized inorganic passing through a semi-transparent anode based on material and thus modifying the electrode work thin PEDOT:PSS and Au metal layers, electricity function. For the investigation of the potential was generated. Photovoltaic performance of devices benefit of buffer layers seen as separating the high were measured and evaluated. This design can be recombination regions of contacts from the light used for smart textiles after further optimization. absorbing layer, we try an analytically solvable method for the determination of "best cases," and Keywords: Inverted organic solar cell, Nano- thus show the maximum achievable beneficial materials, Photovoltaic fiber, ZnO nanoparticles effects. Buffer layers (PeO, ZnO, TiOx etc.) are empirically used to enhance VOC. Generally, textile- INTRODUCTION based materials manufactured in fiber or tape forms Recently, with the increasing world population and are colored, not completely transparent. Therefore, progress in technology, exhaustion of energy these kinds of structures take the light from their resources is a critic issue. Consequently, renewable outer surface. In this study, considering non- energy sources and their improvement are very transparent PET monofilament as the substrate of most popular topics which are studied on, recently photovoltaic fiber. Glass-based and fiber-based [1,2]. Out of renewable energy technologies, organic solar cells were characterized in the dark and photovoltaic cells have a great attraction related to under sun light (100 mW/cm2) simulated using a their admirable properties [3]. Over the last decade, solar simulator under AM 1.5 conditions. organic solar cells attracted attention due to their Photoelectrical parameters including short-circuit unique properties such as flexibility, cost- current (Isc), open-circuit voltage (Voc), fill factor and effectiveness, graded transparency, light, easy power conversion efficiency (η) of the photovoltaic processing techniques, being environmental devices were characterized. friendly, and applicability to both large and small areas. People, far from the electric grids, will be RESULTS AND DISCUSSIONS able to get electricity by photovoltaic textile Following device structures were developed in structures for small electrical devices, such as order to obtain photovoltaic fiber based device music player,mobile phone charger etc. reliminary (Figure 2). An active photovoltaic fiber using studies on developing a fibre showing photovoltaic polymer based solar cell materials and a buffer layer effect were done previously [4- 11] by different was developed successfully. Moderate efficiency groups. Conventional and inverted organic solar was obtained from preliminary studies. cell structures were shown Figure 1.

Figure 2: Inverted photovoltaic device (a) structures Figure 1: The conventional and inverted organic from up and down illumination and Photovoltaic solar cell structures fiber structure (b) using inverted layer sequence

EXPERIMENTAL There are several types of photovoltaics. In this study, inverted type of solar cells are employed. In CONCLUSIONS A photovoltaic fiber generating electricity using inverted layer sequence was developed. From these preliminary studies, moderate efficiency was obtained After further optimization, this photovoltaic structure may be a candidate for electricity generating textiles.

REFERENCES [1] I. Yüksel, Renewable Energy, 2008, 4, 802. [2] P. D. Lund, Renewable Energy, 2009, 34, 53. [3] European Photovoltaic Industry Association [EPIA], Solar Generation V-2008, 2008, Global Market Outlook for Photovoltaics Until 2012, www.epia.org. [4] A. Demir, A. Celik Bedeloglu, I. Borazan, D. Ozdemir, K. Tutuncu, Design of an Organic Photovoltaic Fiber Structure, The Fiber Society Congress, 2011, 36. [5] Bedeloglu (Celik) A, Development of Fibers with Photovoltaic Effects, PhD Thesis, Dokuz Eylül University, İzmir, 2009. [6] O’Connor, B, Pipe, KP, and Shtein, M, Fiber Based Organic Photovoltaic Devices. Appl. Phys. Lett., 2008, 92, 193306. [7] M. Shtein, and SR. Forrest, Organic Devices having a Fiber Structure. US Patent 7194173, 2007. [8] Liu, J, Namboothiry, MAG, and Carroll, DL, Fiber-based Architectures for Organic Photovoltaics. Appl. Phys. Lett., 2007, 90, 063501. [9] A. Bedeloglu, A. Demir, Y. Bozkurt, & N.S. Sariciftci, A flexible textile structure based on polymeric photovoltaics using transparent cathode. Synthetic. Metals, 2009, Vol.159, pp.2043–2047. [10] A. Bedeloglu, A. Demir, Y. Bozkurt, N.S. Sariciftci, A Photovoltaic Fibre Design for. Smart Textiles Textile Research Journal, 2010, Vol.80, No.11, pp.1065-1074. [11] A. Bedeloglu, P. Jimenez, A. Demir, Y. Bozkurt, W. K. Maser, NS. Sariciftci, NS. (2011). Photovoltaic textile structure using polyaniline/carbon nanotube composite materials. The Journal of The Textile Institute, 2011, DOI: 10.1080/00405000.2010.525816, ISSN:1754-2340 (electronic) 0040-5000 (paper). Optimizing Fiber-Based Bioconversion Media for Ammonia/Water Bio-Remediation

Yong K. Kim and Armand F. Lewis Bioengineering Department, U Mass Dartmouth, MA 02747 [email protected]

PURPOSE lab-scale (338.5 liter volume) closed-trickling biofiltration This is a study delineating the geometric and operational systems were constructed to evaluate experimental bio- parameters that control the effectiveness of fiber based media for ammonia/water remediation. Effects such as a bio-media used in bio-filtration devices for the bio- media specific surface area, flock density (number of remediation of ammonia polluted water. flock fibers /mm2), base material structure, and the recirculation flow rate through the various media INTRODUCTION materials were studied. These media configurations were In 2001, Kim and Lewis [Kim et al 2001] reported that evaluated in terms of how well they depleted the textile flocked surfaces are more effective as media for ammonium ions in the deliberately contaminated (with the bio-conversion of ammonia to nitrate ions than un- ammonium hydroxide) water in the apparatus’s holding flocked surfaces. These flocked surfaces are found to be tank. The experimental media effectiveness parameter effective bio-media materials because they have a high used throughout this UMD study has been referred to as and compact surface area. Furthermore, these flocked the Ammonium ion Depletion Rate or ADR. This ADR media materials have been found to be easily cleaned and term is has units of ppm/day (or mg/liter/day) and are re-useable [Sarda 2007]. In continuing research, represents the average daily drop in ammonia attempts have been made to optimize the bioconversion concentration of the system’s approximately 338.5 liter efficiency of these flocked bio-media materials and to ammonia-polluted-water holding tank system. learn more about their operational features and perhaps Experimentally, it was observed that the depletion of come up with an optimal flocked bio-media design. In all ammonia concentration by the microbial bioreaction these relevant studies, ammonia was selected as the model followed a straight line equation given by: + inorganic water pollutant since it is relatively easy to [NH4 ] = C + (ADR) t (3) + biodegrade into a non-toxic nitrate compound. where [NH4 ] is the ammonium ion concentration and t is In the bio-filtration of ammonia in water, nitrifying the time (days) and C is a numerical constant. From the bacteria such as nitrosomonas and nitrobacter are used to observed linear equation, the slope of the determined line oxidize ammonium ions to nitrite and then to nitrate. was recorded as the ADR for particular media “run” and These are the traditional micro-biological species used in water flow rate. This linear behavior signifies that the bio-filtration devices for closed-system aquaculture bio-conversion induced reduction in the water’s ammonia operations and domestic aquariums [Westerman, P. W. et concentration is a zeroth order bio-chemical reaction; al 1996] [Kaiser, G. E. et al 1983]. In an operating signifying that the reaction rate is independent of the aquaculture system, ammonia polluted water from an water’s ammonia concentration (2-20 ppm range in this aquaculture fish holding tank is pumped (circulated) into study). This linear behavior was unexpected since it is an ancillary bio-filtration tank where it comes in contact well established that the kinetics of ammonia depletion with a mass of porous bio-media which is in turn coated rate in water in the 4 ppm down to 0 ppm range has been with a nitrifying bacterial film. The bacteria that inhabit shown to follow first order kinetics. [Timmons, 2010]. the film oxidize the ammonium ions present in the passing water into nitrite and further to nitrate ions. The RESULTS AND DISCUSSION overall biochemical nitrification reaction is given by The detailed relationships of the water flow rate and the [Ebling et.al. 2006] [Chen et. al. 2006]: ammonium depletion rate were determined on a diverse series of bio-media materials including commercially + - NH4 + 1.83O2 + 1.98HCO3 0.021C5H7O2N available and experimentally fabricated bio-media - + 0.98NO3 + 1.041H2O + 1.88H2CO3 (2) configurations. The overall scope of these UMD experiments involved measuring the ADR values for all In this bio-reaction, the nitrifying micro-bacteria the bio-media materials at four water flow rates; 1.9, 5.7, metabolize or get energy from the ammonium ions 9.5 and 13.3 liters/minute. Comparing the ADR data for present in the polluted water. all the media shows that the Double-Side Flocked Nonwoven (DSFN) has the highest measured ADR value. APPROACH It was found to be superior to the various commercial bio- In the present UMD bio-media studies, various flocked media tested. This supports the previous observation that bioconversion media and their ‘controls’ were prepared flocked surfaces are found to provide a design advantage and tested for their effectiveness in terms of their when developing bio-media materials for bioremediation measured ammonium ion depletion rate. To do this, two applications. In addition, an important bio-media material behavior of indicting that ADR values increase as the effectiveness parameter, it is shown that the heavily bulk surface area of the bio-media material increases. flocked DSFN experimental bio-media is by far inherently more effective bio-media material for ammonia Detailed review of the water flow rate data has uncovered in water bioremediation. a potentially important new empirical bio-media material design parameter. This development can be illustrated by CONCLUSIONS examining plots of ADR vs. water flow rate data as Carrying out experiments at various recirculation water presented in Figure 1. These data clearly show a flow rates has shown that these ADR values for various ubiquitous downward trend in ADR value as the water media can be modeled as a function of water flow rate flow rate increases. In an additional step it was using a polynomial equation. Using this empirical determined that the data in Figures 1 could be fit in terms equation, the ADR data can be extrapolated to a of a simple second order polynomial model: hypothetical “zero” water recirculation rate; this extrapolated ADR value has been called the “intrinsic” 2 ADR = ADR(i) + A (Wf) + B (Wf) (4) ADR or ADR(i). It represents the hypothetical “inherent” ability of the media material to bio-react with the where A and B are numerical constants. Now, by ammonia contaminated water when polluted water in extrapolating Wf to a “hypothetical zero flow rate a new contact with the media bio-film is not flowing; meaning it empirical parameter denoting an “Intrinsic” value for the is in quiescent equilibrium with the ammonia ammonia depletion rate is obtained. This new parameter contaminated water. This new empirical parameter is has been called the “Intrinsic Ammonia Depletion Rate” being proposed as an inherent property of a bio-media for a bio-media and is designated as ADR(i) [Sun, 2012]. material. It is proposed that ADR(i) values can now be This Intrinsic Ammonia Depletion Rate parameter can be used to rate the ammonia-in-water bioremediation interpreted in terms of being the ADR value for the bio- effectiveness of various bio-media materials. It should be media when it is placed in stationary, non-moving a useful parameter in the search for an optimum bio- reservoir of ammonia contaminated water. media material.

FUTURE WORK The operational function of these flocked experimental bio-media materials should be evaluated in an actual aquaculture field application. Also a study of the effect of surface area of flocked substrate materials will be studied in order to establish a correlation between surface area and the ADR of experimental bio-media.

REFERENCES

1. Ebling, J. M., Timmons, M. B., Bisogni, J. J., “Engineering Analysis of the Stoichiometry of Photoautotrophic, Autotrophic and Hetrotrophic Control of Ammonia-Nitrogen in Aquaculture Figure 1. Polynomial Fit of Ammonium Depletion Rate Systems” , Aquaculture 257:346-358 (2006). versus Water Flow Rate Data Flocked Special Material 2. Kaiser, G.E., Wheaton, F.W., “Nitrification Filters for (SFM), Adhesive Coated Special Material (ACSM), Aquatic Culture Systems,” Journal of World Mariculture Society,14, 302-307 (1983). DSFN and Perforated DSFN (PDSFN) 3. Kim, Y. K. and A. F. Lewis, “Compact Floor-Space Saving Biofilters for Land Based Aquaculture Applications,” State of Table I. Determination of Intrinsic Ammonia Depletion Massachusetts STEP Program, Year 1 final report, August 29, Rates, ADR(i) for Various Bio-Media Materials 2001. 2 Bio- Derived Polynomial Equation R value ADR(i) 4. Sarda, P. K. “Novel Fiber Based Bioconversion/Bio-Filtration (a) Media (1) Media Materials” M. S. Thesis , UMass-Dartmouth August DSFN ADR = 5.21 + 0.0084Wf + 0.934 5.21 2 2007. 0.396(Wf) 5. Sun, Yu, “Optimizing the Bioconversion Capability of PDSFN ADR = 4.49 + 0.0051Wf + 0.835 4.49 0.033(W )2 Flocked Bio-filtration Media Materials”, M. S. Thesis in Textile f Technology, University of Massachusetts-Dartmouth, FSM ADR = 3.90 + 0.0146Wf + 0.983 3.90 2 0.393(Wf) Department of Bioengineering, August 2012. ACSM ADR = 2.41 + 0.0166Wf + 0.998 2.41 6. Timmons, M.B., J. M. Ebling, “ Recirculating Aquaculture”, 2 0.292(Wf) Cayuga Aqua Ventures, Ithaca, NY, 2010. (a) ADR(i) values are obtained by setting Wf to zero in each 7. Westerman, P.W., Losordo, T.M. and Wildhaber, M.L., equation. “Evaluation of Various Bio-filters in an Intensive Recirculating Fish Production Facility,” Transaction of the A table of the second order polynomial equations and the American Society of Agricultural Engineers, 39, 723-727 ADR values obtained from Figures 1 are tabulated in (1996). (i) Table I. From this analysis and the newly defined ADR(i) 3D Woven Fabrics as Filtration Media in a Membrane Bioreactor for Wastewater Treatment

Fang Zhao, Bubi Jing, Hong Chen, Fujun Xu, Lan Yao, Yiping Qiu College of Textiles, Donghua University, Shanghai 201620, China [email protected]

OBJECTIVE The objective of this study is to investigate the was used as Z yarns and warp yarns, and nylon air wastewater treatment effect by using 3D orthogonal textured yarns were introduced (45danie) as weft yarns. woven fabrics as filtration media in membrane bioreactors The satin weave offered the smooth surface of the fabric (MBR) technology. Compared with other four high which benefit for cake discharge and reducing membrane density filter fabrics, the application of 3D structure filter fouling. R1-R4 were all made of nylon high-density was a new approach and could facilitate better retention monofilament, parameters of which were particularly of pollutant particle. shown in Table I. The total filtration area was 0.012m2. These fabrics were used as filtration units in short-term INTRODUCTION experiments to elucidate the effect of wastewater The MBR has been proposed as an important liquid–solid treatment on MBR operation. separation technology due to its high biomass Fig. 3 showed the 3D filtration membranes used in this concentration which provides a better removal of nutrient study. Deep pore structure between warp and weft yarns and improves effluent quality significantly. Fig.1 in R5 could be seen clearly, and from the picture illustrates the membrane bioreactor sketch. In this system, apertures of R5 are much larger than those of others. module units are dipped in activated sludge aeration tank. However, control of membrane fouling and high cost of RESULTS AND DISCUSSION the membrane materials and expensive operational cost Filtration resistance analysis limit the range of application of MBR technology [1]. The flux can usually be described by using a theoretical There are considerable investigations focusing on model known as the resistance-in-series model [3] as development of low-cost filters, mainly including: non- follows: wovens, meshes and filter cloths [2]. In this study, a new p 1 p  1  type of 3D woven fabric was adopted as filter unit in an J  ( )     Rt   Rf  Rm  Rc  MBR, compared with four other high density 2D fabrics. The 3D woven fabric was made of nylon monofilament and nylon air textured yarn with 30μm average pore size. Structural morphology differences between 3D woven fabric and 2D fabrics were shown by 3D digital microscope analysis. The effectiveness of 3D fabric as solid–liquid separation media was further shown by performing flux and turbidity test on processing wastewater.

FIGURE 2. Structure diagram of 3-D woven fabric

Table I characteristics of the fabric material Parameter R1 R2 R3 R4 R5 Pore size 37 42 21 18 80

Linear density 50 20 20 20 20 (daniel) 45 FIGURE 1. The sketch of the membrane bioreactor and Warp operation 1745 1400 1850 2140 2346 count(num/10cm) Weft APPROACH 1635 1230 1820 1895 200 The structure of the 3D woven fabric (R5) is shown in Fig. count(num/10cm) 2, which is formed with satin structure and made of four- layers of nylon yarns. Nylon monofilament (50 danie)

(a) (b) (c)

(d) (e) FIGURE 4. Initial tap water flux and wastewater flux in membrane bioreactor (MBR) pilot test FIGURE 3. Images: (a)R1: 2/2twill (b)R2:3/3twill(c) R3: 3/3twill (d) R4: 4/4twill (e) R5: 3D woven where J is the permeate flux (m3/m2s), ΔP is the trans- filter pressure(Pa), μ is the viscosity of permeate (Pa.s), Rt is the total filtration resistance(1/m), Rm is the filter resistance (1/m), Rf is the fouling resistance caused by pore blocking onto the filter pore wall or surface (1/m). Rc the cake resistance (1/m), Rt is an index of the extent of fouling and the ease of filtration under specific conditions. p Rm  Js where Js is the initial tap water flux. p Rc   Rm  Rt FIGURE 5. Turbidity analysis of five fabrics JAs where Jas is the flux of activated sludge at steady state CONCLUSION [4]. Application of 3D fabric materials in MBRs demonstrated The initial tap water flux and wastewater flux in that 3D woven materials performed better than 2D fabrics membrane bioreactor pilot test is shown in Figure 4. The as solid–liquid separation media in wastewater treatment, trans-membrane pressure was maintained at 15 KPa for its lowest turbidity and much higher flux at proper throughout the initial tap flux test period. While during operating condition. An appropriate operating strategy the wastewater flux test, the trans-membrane pressure was such as devised fabric parameters is required for long- maintained at 0.08Mpa, which is a little higher than the term stable operation in the application of 3D woven 2D fabrics. (The other four are maintained at 40 KPa).It is fabrics in MBR. clearly seen that R5 fabric has the highest flux under proper operating condition. The results also demonstrated ACKNOWLEDGMENT that the pore size was proportional to flux, and the small This work was supported by the State Key Program of pore was apt to be blocked in the filtration process. National Natural Science of China (No.51035003) and the Fundamental Research Funds for the Central Universities. Efficiency of the treatment The turbidity of the filtrate is shown in Figure 5. The REFERENCES treatment efficiency and quality of the five fabrics showed [1] Tatsuki Matsuo. Advanced technical textile products, significant difference. However, the lower turbidity is Textile Progress,40:3, 123-181. obtained with the higher yarn density under the same [2] Waleed M. Zahid , Saber A. Use of cloth-media filter fabric structure such as R2 and R3. R4 can generate for membrane bioreactor treating municipal wastewater, micron sized pore for its 4/4 structure. Although the Bioresource Technology 102 (2011): 2193–2198. largest pore size of R5 was 80μm, much larger than 15μm [3] Richard Wakeman,The influence of particle properties of specimens R4, it still showed the lowest turbidity on filtration. Separation and Purification Technology 58 among these fabrics, mainly due to its depth filtration and (2007) 234–241. the perfect retention of particles of the textured yarns as [4] M.Mulder. Basic Principles of Membrane Technology, weft yarns. Kluwer Academic Publishers, Dordrecht, The Netherlands, 2000.

Thermal and Spectroscopic Properties

Atomic Force Microscope-Based Infrared Spectroscopy of Single Fibers

Michael Lo1, Qichi Hu1, Curtis Marcott2, Craig B. Prater1, Kevin Kjoller1 1Anasys Instruments Corp., Santa Barbara, CA, 2 Light Light Solutions, LLC., Athens, GA [email protected]

OBJECTIVE Using atomic force microscopy (AFM)-based nanoscale infrared (IR) spectroscopy, the chemical identities and relative IR absorption band ratios of single fibers with sub-micrometer diameters are obtained.

INTRODUCTION Traditional IR spectroscopy of bulk fibers provides an average of all absorptions in the path of radiation. Variations within a small sub-population of the sampling volume may not be detectable. Infrared microspectroscopy enables spatially resolved IR spectroscopy, but the spatial resolution is limited by diffraction. This provides significant challenges for the analysis of individual fibers with diameters smaller than the wavelength of infrared radiation. In addition to the inability to resolve sub-wavelength heterogeneity, weak sensitivity and distortions in the IR spectral bandshapes can occur. To overcome these limitations, we have applied the technique of AFM-based infrared spectroscopy (AFM-IR) to obtain infrared spectra of individual fibers with a high signal to noise ratio. This AFM-IR approach illuminates a sample with a broadly tunable IR laser and uses the tip of the AFM to detect Figure 1. A 10 μm x 6 μm AFM image (top) and AFM- the local thermal expansion of the material upon IR spectrum (bottom) of a Kevlar fiber; a one-point absorption of IR radiation pulses.1 Standard AFM tips, smoothing routine is applied to the spectrum using which have radii of tens of nanometers, are used to Anasys Instrument’s Analysis Studio version 3.5 detect the ringing motions caused by local thermal expansion of the sample underneath and are responsible CONCLUSION for achieving high spatial resolution below the Using AFM-IR spectroscopy, the chemical nature of diffraction limit (ca. 100 – 200 nm).2 The amplitude of single, isolated fibers can be readily determined despite the ringing motion is proportional to the absorptivity of the fact that the overall diameter of a fiber is the sample, and hence the resulting AFM-IR spectra are significantly smaller than the infrared wavelengths used comparable to conventional infrared spectra. By to make the measurement. Not only does this extend the varying the polarization of the incident radiation, it is spatial resolution of the infrared spectroscopy beyond also possible to study orientation of the polymer fiber the diffraction limit, but may also permit the analysis of chains. fiber mixtures at high spatial resolution.

RESULTS AND DISCUSSION KEYWORDS An AFM-IR spectrum is readily obtained from a single AFM, AFM-IR, fiber, infrared spectroscopy fiber. For instance in Figure 1, the upper image shows an AFM image of a single Kevlar fiber affixed directly ACKNOWLEDGMENT on the surface of a zinc selenide (ZnSe) prism. At the The authors would like to thank Bruce Chase for location where the AFM-IR spectrum is obtained, the supplying the sample. thickness of the fiber is about 1.3 μm. The amide-I band at 1648 cm-1 is readily detected, along with the aryl C=C REFERENCES stretches at 1512 and 1600 cm-1. This is consistent with 1. Dazzi et. al. J. Appl. Phys. 2010, 107, 124519. infrared absorption characteristics of a polyaramide 2. Marcott et. al. Appl. Spectrosc. 2011, 65, 1145. (Kevlar). Chemistries of fibers can be readily obtained using this AFM-IR technique. The Response of a Nylon-Cotton Fabric to High Heat Flux

Thomas Godfrey, Margaret Auerbach, Gary Proulx, Pearl Yip, Michael Grady US Army Natick Soldier RDE Center [email protected]

OBJECTIVE APPROACH A one dimensional numerical model for transient heat The models here treat the transient through-the-thickness conduction, incorporating material transformations conduction of heat in the fabric, where the fabric is described by chemical kinetics, is used to investigate the considered a one dimensional composite slab exposed to a response of a 230 g/m2 50/50 nylon-cotton blend fabric to radiant heat flux on its outer surface, and subject to high radiant heat fluxes in bench level thermal protection contact with another material layer on its inner surface. and flammability tests. The modeling results are The approach differs from that of other workers [3-5] in compared to experimental results obtained in the Thermal that the individual components making up the fabric slab Barrier Test Apparatus (TBTA) and cone calorimeter may undergo transformations or reactions, where reaction testing. rates are governed by chemical kinetics with appropriate exo- or endothermic contributions to the energy balance. INTRODUCTION The models are implemented in the Therma-Kin American soldiers and marines involved in the recent computational tool [1], which was originally developed to conflicts in Iraq and Afghanistan have suffered increased model bench-scale fire calorimeter tests of materials [2]. incidence of burn injury, often as a direct result of exposure to improvised explosive devices. Accordingly, Since the configuration of cone calorimeter tests does not providing dismounted soldiers with protection against involve an air gap behind the material sample, it is battlefield flame and thermal hazards has been made a difficult to include such gaps when using the Therma-Kin high priority. The standard Army Combat Uniform tool. Usually, behind fabric air gaps are included in bench (ACU) fabric is woven using blended yarns of 50% nylon level fabric thermal protection tests, and in models of staple - 50 % cotton fiber. While the fabric provides for a fabric thermal protective performance [3-5], since air gaps durable and comfortable combat uniform, when caused to of various thicknesses are present in garments worn on burn it is not self-extinguishing, and is therefore not the human form. Here the TBTA tests are done with the considered flame resistant in the conventional sense of the back surface of the fabric layer in contact with the heat term’s usage in protective clothing. Nonetheless, it is of flux sensor surface to accommodate modeling limitations. interest here to investigate its thermal performance The water cooled heat flux sensor is modeled as a slab of characteristics in order to understand conditions under copper with a convection boundary condition on its back- which it may provide sufficient protection. In addition, face. The “transmitted” heat flux is determined in the efforts are underway to develop surface treatments for the modeling results by numerical differentiation of the ACU fabric through which its flame resistance can be predicted spatial temperature distribution in the copper improved; a better fundamental understanding of the base slab. fabric performance is of value. To provide property values needed in the model, In this work, the Therma-Kin [1] computational modeling extensive use is made of Differential Scanning tool is used to develop models for the transient response Calorimetry (DSC) and an instrument providing of the ACU nylon-cotton fabric undergoing thermal simultaneous DSC and Thermo-gravimetric Analysis testing. A thermal protection test, using the TBTA, (TGA). The specific heats of nylon and cotton fibers are exposes the surface of a fabric swatch to a square wave modeled as linearly dependent on temperature based on radiant heat flux and measures the heat flux transmitted measurements made using the Modulated DSC technique. behind the fabric to a water-cooled sensor. The Simultaneous DSC-TGA is used to quantify the kinetic transmitted heat flux time history may be analyzed using parameters and enthalpies of nylon and cotton thermal a skin burn injury model to determine the likely severity decomposition. The heat of fusion of nylon fibers was of injury that would result to human skin protected by the quantified for both melting and solidification by fabric layer. A flammability test is performed using a conventional DSC. The enthalpy of moisture desorption cone calorimeter [2]; the fabric swatch is heated via a and vaporization is taken from literature values [6]. cone shaped radiant heater in the presence of an ignition source until flaming combustion of the sample occurs and The thermal conductivity of the nylon-cotton fabric is the sample burns out. Mass loss, heat release rate, time to determined over a range of temperatures from ignition, and duration of flaming combustion are measurements on pads of multiple fabric layers in a measured. Modeling results for the TBTA and cone tests Rapid-k heat flow meter apparatus using a procedure will be compared to the experimental observations. similar to that described by Lawson and Pinder [7]. The effective thermal conductivity of a fabric layer is considered to be linearly dependent on temperature. To mass flux of 5×10-4 kg/m2-s. implement thermal conductivities in the Therma-Kin modeling framework, the fiber component thermal conductivities were selected such that the nylon/cotton/air composite slab representing the fabric layer exhibits the measured effective behavior.

To properly model the interaction between the fabric layer and the radiant heat sources, effective gray body emissivities for the fabric were calculated based on measured reflectances over a range of wavelengths and Figure 2. Mass loss rate in cone calorimeter tests, 25 kW/m2 heat flux. the radiation spectra of the source. The bank of quartz Solid line – modeling results. Dotted lines – experimental replicates. lamps in the TBTA were treated as a 2300 K blackbody radiator and the cone heater was treated as a 870 K The modeling results for mass loss rate (Fig. 2) are seen blackbody radiator. to be separated into two peaks, the earlier peak consisting of cotton and the later more gradual peak consisting of RESULTS AND DISCUSSION nylon. This behavior is not seen in the experimental Experimental and modeling results for a thermal results. A partial explanation may be the oversimplified protection test are exhibited in Fig. 1. The fabric swatch is kinetics assumed in the model, where cotton is taken as exposed to a square wave heat flux pulse of nominal decomposing in a single step, whereas TGA experiments intensity 90 kW/m2 and five seconds in duration in the indicate a second slower decomposition step occurring. TBTA. The heat flux transmitted through the back face of Time to ignition is 15 s in the simulation in agreement the fabric is measured by a Gardon gauge in contact with with the experimental results. the back of the fabric sample. ACKNOWLEDGMENT – The effort and expertise of Mr. Randy Harris, WPI Fire Protection Lab, in performing the cone tests is greatly appreciated.

REFERENCES [1] Stoliarov, S. I., and Lyon, R. E., “Thermo-Kinetic Model of Burning,” Federal Aviation Administration William J. Hughes Technical Center, Atlantic City International Airport, NJ, Report No. DOT/FAA/AR- TN08/17, May 2008.

Figure 1. Thermal protection test in TBTA, 90 kW/m2 incident heat flux, [2] ASTM E 1354, “Standard Test Method for Heat and 5 s duration. Solid blue line – model, high moisture. Solid red line – Visible Smoke Release Rates for Materials and model, low moisture. Lines with symbols – experiments. Products Using an Oxygen Consumption Calorimeter,” ASTM International, West Desorption and evaporation of moisture in the fabric Conshohocken, PA, 2011. requires a significant amount of heat energy. As such, [3] Torvi, D. A., and Threlfall, T. G., “Heat Transfer moisture content has an important effect on the heat flux Model of Flame Resistant Fabrics During Cooling transmitted through the fabric back face, as exhibited in After Exposure to Fire,” Fire Technology, 42, pp. 27- the modeling results in Fig. 1. Melting of the nylon 48 (2006). component in the fabric also has a small effect which can [4] Torvi, D. A., and Dale, J. D., “Heat Transfer in Thin be seen in the drop in the transmitted flux that occurs after Fibrous Materials Under High Heat Flux,” Fire three seconds of exposure for the low moisture case. Technology, 35, pp. 210-231 (1999). Agreement with the two experimental replicates shown is [5] Song, G., Barker, R. L., Hamouda, H., Kuznetsov, A., good. Thermal decomposition of cotton and nylon does V., Chitrphiromsri, P., Grimes, R. V., “Modeling the not affect the modeling results for transmitted heat flux in Thermal Protective Performance of Heat Resistant this test under the selected conditions. Garments in Flash Fire Exposures,” Textile Research Journal, 74(12), pp. 1033-1040 (2004). Cone calorimeter tests were performed at an incident heat [6] Morton, W. E., and Hearle, J. W. S., Physical 2 flux of 25 kW/m . In the sample holder, the fabric is Properties of Textile Fibers, John Wiley & Sons, New backed by aluminum foil and supported on an insulating York, 1975. TM ceramic wool (Kaowool ) blanket. For the cone test [7] Lawson, J. R., and Pinder, T. A., “Estimates of simulation, the fabric layer was modeled as supported by Thermal Conductivity for Materials Used in Fire a 13 mm thick ceramic wool layer with an insulated back- Fighters’ Protective Clothing,” National Institute of face boundary condition. It should be noted that flaming Standards and Technology, Building and Fire combustion is modeled as an additional heat flux on the Research Laboratory, Gaithersburg, MD, Report No. 2 sample of 12 kW/m . Ignition is assumed to occur at a NISTIR 6512, May 2000. A Study and a Design Criterion for Multilayer Structure in Perspiration-Based Infrared Camouflage

Xia Yin1, Qun Chen2, Ning Pan1 1Department of Biological and Agricultural Engineering, Division of Textiles & Clothing, University of California at Davis, CA 95616, USA 2 Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China [email protected]; [email protected]

INTRODUCTION Methods Human body emits infrared rays in the mid-far infrared In order to simulate both human body heat transfer and radiation range that can be detected by infrared cameras, skin sweating, a measuring apparatus is set up in our lab as long as there is a sufficient difference between the as illustrated in Fig. 2 temperatures of the body and the surroundings. Current technologies used to accomplish the infrared camouflage all rely on external or additional resources, ignoring that our human body actually has its own heat dissipation capability sufficient for the purpose.

The human body itself has two ways to dissipate the heat generated: the sensible heat dissipation via skin surface temperature and the latent heat release through the evaporation of perspiration. When dissipation through sensible heat transfer is not sufficient to release the basal body heat, our body will spontaneously sweat to dissipate Figure 2 The schematic diagram of the measuring apparatus heat by latent heat transfer. Thus, if the sensible heat The three-layer sample is put on the hot plate and the release is effectively suppressed and the heat dissipation temperature of its bottom side of the 1st layer is from the sweat phase change (liquid to gas) is sufficiently maintained at 34oC, replicating the body skin temperature. large, the temperature difference between the clothed The water at around 34oC is added from the bottom human body and the environment will be diminished to surface of the sample by a tube connected to a syringe the degree that the body becomes infrared camouflaged. pump, simulating the sweat supply from human body. An

infrared camera, fixed directly above the three-layer Based on this new idea, a new scheme of perspiration sample, is used to record our target temperature at the based infrared camouflage and the corresponding multi- upper surface of the 3rd layer (outer surface temperature). layer cloth prototype possessing such functions of The ambient temperature is stable at around 22oC, and the restraining the sensible heat transfer while facilitating the relative humidity of the ambient is about 42%. latent heat transfer of the human body were proposed recently by the present authors. In this paper, we reported Evaporative Cooling Effect our recent work to validate both the idea and the cloth We prepared two samples of the same three-layer prototype. structure: Sample A was covered with a piece of thin

plastic film, while Sample B was not. Thus, once the EXPERIMENTS AND RESULTS water is added into the samples, evaporation can take Materials place only in Sample B. Due to the structural similarity with the prototype we

proposed, the commercial multilayer incontinence pads ) Adding

C water Sample B were used as samples to study how such actual layered o ( After 34 Before systems behave. The internal structures of the used three adding Sample A adding layers in a pad are shown in Fig.1 32 A Twet1 T 30 dry 5 oC 28 B T 26 wet2 24

The 1st layer (I) The 2nd layer (II) The 3rd layer (III) Outer surface temperature 0 500 1000 1500 2000 2500 Time (s) Figure 1 The photographs of internal morphology for the three layers used in experiments Figure 3 Comparison in outer surface temperature between Sample A and Sample B Fig.3 shown that both samples have the same dry DISCUSSION temperature (Tdry) before adding water. But after adding Theoretical predictions versus Experimental data water, Sample A stabilized at a temperature Twet1 > Tdry., A theoretical model at the steady-state based on our while Sample B decreased to a stable temperature (Twet2) experimental conditions was made. Both the theoretical o that is not only 5 C lower than that of Sample A (Twet1), and experimental values of outer surface temperature for but even lower than the dry temperature. The fact that various samples are put together and shown in Fig.6 Twet2 < Tdry demonstrated the potential and effectiveness of T / oC using evaporation for infrared camouflage. 3

Dry state Wet state without Wet state with The Thickness Effect evaporation evaporation By changing the thickness of the 3rd layer, we have three samples from Sample B to Sample D with increased total thickness. The samples were not wrapped with plastic film so evaporation was allowed during the testing. ) C

o 38 ( Sample D 36 Sample C Samples 34 Sample B Figure 6 Theoretical values versus experimental values in outer 32 surface temperature of the samples

30 B All the theoretical predictions and experimental values 28 C match each other well. Sample A in the wet state D B 26 C possessed the highest outer surface temperature, because 24 D the added water reduced the heat resistance to sensible

Outer surface temperature temperature surface Outer 0 500 1000 1500 2000 2500 heat transfer, and with no evaporation at all to cool it off. Time (s) Meanwhile, for each of the remaining samples (Samples B, C, D, or E), due to evaporation in the wet state, the Figure 4 Comparison in outer surface temperature among three outer surface temperatures (right part in Fig. 6) are lower samples with different thickness than when they were in dry state (left part in Fig. 6). With In dry state, the thicker the sample, the lower its steady- the increase of the sample thickness (from Sample B to state temperature. Once into the steady state after adding Sample E, and in both dry and wet state), the surface water, the thicker sample again maintained a lower outer temperature all decreases. To sum up, sweat evaporation surface temperature. Thus, we can lower the targeted and a greater sample thickness both reduce the outer temperature by increasing the sample thickness. When we surface temperature as predicted theoretically and increased the total thickness to 2.58cm (Sample E), the validated by experimental data in this study. outer surface temperature descended to 22.5oC at the final steady state shown in Fig.5, that is just 0.5oC higher than Heat Flux Analysis – a design criterion the ambient, reaching the goal of infrared camouflage. Heat flux calculation shows clearly the effectiveness of body heat dissipation via evaporation. By comparing the 36 Hot plate changes in the ratio of latent heat flux to the sensible heat flux (q /q ) and the outer surface temperature, it is clear ) 34 l s C Bottom surface of the sample that this ratio q /q can be used as the criterion in o l s ( 32 reflecting the performance of a cloth system for the 30 perspiration based infrared camouflage. The higher the 28 Upper surface of the sample ratio, the lower the outer surface temperature. 26 Furthermore, as this ratio dictates the heat-moisture 24 Ambient Temperature balance in a cloth system, it can be directly extended to 22 meet the comfort requirement in normal cloth design. 0 500 1000 1500 2000 2500 3000

Time (s) CONCLUSIONS Figure 5 The sample with a thickness for outer surface Both sweat evaporation and a greater sample thickness temperature equal to the ambient reduce infrared detect-ability as predicted theoretically and validated by experimental data in this study. Further, The Layer Sequence Effect the ratio ql /qs can be used as the criterion in reflecting the For a three-layer sample, we can have totally six samples performance of a cloth system for the perspiration based with different sequence combinations. We learnt that infrared camouflage. However, the multi-layer pads used layer III should be on the top, it matters less whether for testing were not optimized for our need, and the Layer I or Layer II is in contact with the skin for the system design and individual layers have to be revised for thermal behavior of the system. But for the sake of better infrared camouflage function. comfort, it is better to have the hydrophobic Layer I contacting the body skin. Thermal Protective Performance of Protective Clothing Upon Steam and Hot Liquid Splash

Farzan Gholamreza1, Guowen Song1, Mark Ackerman2 1Department of Human Ecology, University of Alberta, Edmonton, Canada 2Department of Mechanical Engineering, University of Alberta, Edmonton, Canada [email protected]; [email protected]

INTRODUCTION degree burn from iterative tests and the stored energy Heated protective clothing can deliver thermal energy to model were compared to show the validity of the model. human skin and cause skin burn injuries. After exposure, the thermal energy that is stored within the garment may By employing the aforementioned criteria to determine be discharged to human skin. Due to the complexity of the minimum exposure time, the thermal behavior of the human body movements, the stored energy within the fabric systems upon hot liquid and steam, considering garment would be transferred naturally or by compression stored energy (with and without pressure) and its of the garment against the human body before the contribution to skin burn injury, were analyzed. protective clothing system cools off. This phenomenon can cause exacerbate burns. There are some studies on the APPROACH thermal stored energy within garments exposed to radiant The fabric systems selected for this purpose represent the heat 1-4. In these studies, it is claimed that stored thermal thermal protective garments worn by firefighters and energy released from the fabric systems lowers the industrial workers (Table I). performance of the thermal protective clothing. Song et al. ascertained that the amount of stored energy obtained Table I. Structural features of the fabrics. Weave Surface during thermal exposure could be discharged during the Fabrics Fiber content cooling period through compression and causes skin burn Structure Property 60% Kevlar/ 5-6 Fabric A Plain Finished injuries. In their latter studies , they introduced a 40% PBI minimum exposure time (MET) and the stored energy Fabric B Blue FR fabric Twill Finished coefficient (SEC). These terms are introduced to address Vapro® Moisture + Poly- Plain ----- the stored thermal energy and its contribution to second- Barrier degree burn. Urethane Thermal Fleeced napped 100% Nomex® ----- Liner A both side Although a considerable amount of attention has been Thermal 100% Nomex® Quilted ----- paid to the thermal performance of fabric systems against Liner B convective and radiant exposures, few studies have been done to analyze and measure the stored energy in other The fabric systems were exposed to steam at 1500C. The thermal hazards such as steam and hot liquids. A study conditioned test samples of fabric system were placed on was performed to analyze the mechanisms of and relevant a Teflon-plated sample holder which is equipped with a factors associated with thermal protection provided by skin stimulant sensor. The generated steam was impinged clothing upon hot liquid splash and the thermal stored upon the fabric sample vertically at a pressure of 200 kPa. energy using stored energy model. However, the study The fabric systems were also exposed to hot water focused on thermal energy, which is naturally discharged horizontally at a flow rate of 1000ml/30sec to gauge the to skin upon hot liquid splash 6. effect of the thermal stored energy and fabrics system. The data acquisition system was recording the calorimeter In this study, the thermal performance of thermal output and the programmed software was employed to protective clothing upon hot liquid splash and steam were obtain the second degree burn times using Henriques’ analyzed with compression (SE_C) and without burn criteria5. In each test, 5 seconds after exposure had compression (SE_N) to evaluate the minimum protection ended, the test specimen was compressed against the data of fabric systems upon these hazards. An iterative method collection sensor at a pressure of 13.8±0.7 kPa (2.0±0.1 was employed to find the minimum exposure time psi). This load could possibly simulate individuals regular required for skin burn injury. In addition, the stored activities dealing with hot liquid splash or steam such as energy coefficient, which demonstrates the proportion of leaning, squatting or sitting (according to ASTM standard the discharged energy (cooling phase) in skin burn injury, F 2731-10). is calculated. Using the stored energy coefficient (SEC) and the second-degree burn time, the minimum exposure The following procedure is implemented for hot liquid time causing second-degree burn was calculated. The splash and steam tests (with and without compression): predicted exposure times required to generate a second- For the first test, the specimen was exposed until the second-degree burn occurred (Burn time approach). The energy is discharged when heated clothing is compressed second test was run using the second-degree burn time during the cooling phase. An analysis of the discharged determined from the first test as the exposure time. This energy to the sensors in permeable double-layer fabric was manipulated to make sure that second-degree burn system also shows thicker fabrics store more thermal and exposure end took place simultaneously to minimize energy. However, when compression is applied, more the exposure effect on the cooling period’s stored energy. energy is discharged to the sensor when the fabric system The data acquisition system continued recording the is thicker. Key factors that influence the thermal stored discharged energy in the system after exposure had ended. energy coefficient upon hot water and steam are: the Based on the discharged and the transmitted energy, the fabric’s air permeability, thickness, and surface finishing. minimum exposure time was calculated for each specimen (Cooling phase approach).The third test was run CONCLUSION with the calculated minimum exposure time to find the The focus of this study was to analyze the transmitted and predicted minimum exposure time (MET approach). discharged energy to the skin and analyze the stored energy within the garment upon steam and hot water RESULTS AND DISCUSSION splash. In a real-life scenario, firefighters and industrial The predicted second degree burn time and stored energy workers may be exposed to hot water and steam. Due to coefficient and minimum exposure time were calculated the complexity of the individuals’ movements, the with and without compression for single layer, double thermal stored energy may be discharged and may cause layer and multilayer fabric systems. Also, the minimum severe burn injuries. By employing the described criteria exposure time was calculated employing the iterative to find the minimum exposure time, dominant factors method and the stored energy model6. The values influencing the fabrics’ thermal properties upon hot liquid obtained from the calculated and predicted minimum splash and steam are introduced. The understanding of the exposure time upon hot water splash and steam give more amount of thermal transmitted and discharged energy to validity to the stored energy model. the skin obtained from this work will enable the engineering of textile materials to achieve high The data used in the analyses shown in Table II is the performance protection from these hazards. average of three tests derived from selected fabrics S-1 (Fabric A), D-1 (Fabric A+ moisture barrier) and M-1 FUTURE WORK (Fabric A + moisture barrier + thermal liner A) within In a future study, a variety of loads, under different each fabric system. compression times, would be used to simulate fire fighters and industrial workers various activities and movements. Analyses of the absorbed energy by the sensors during the cooling phase (after exposure ends) and the stored energy REFERENCES coefficient showed that stored thermal energy contributes 1. Song G, Paskaluk S, Sati R, Crown E, Dale J and significantly to the second-degree burns. The bulk hot Ackerman M. Thermal protective performance of water and steam motion through the permeable porous protective clothing used for low radiant heat protection. structure of the fabric enhances the heat transfer and Textile Res J 2010; 81(3): 311–323. decreases the thermal performance of thermal protective 2. Barker RL, Guerth C, Behnke WP and Bender M. clothing upon steam and hot liquid splash. Therefore, Measuring the thermal energy stored in firefighter resistance to mass transfer is proven to be the key factor protective clothing. In: Nelson CN and Henry NW (eds) for reducing the amount of transmitted and discharged Performance of Protective Clothing: Issues and Priorities thermal energy to the skin. Thus, air permeability is a for the 21st Century: 7th Volume ASTM STP 1386. West dominant factor in the protection performance against hot Conshohocken PA: American Society for Testing and liquid splash and steam. Materials, 2000, pp.33–44. 3. Song G, Barker RL, Hamouda H, Kuznetsov AV, Table II. Data obtained from the sensors exposed to hot Chitrphiromsri P and Grimes RV. Modeling the thermal water (Horizontal exposure). protective performance of heat resistant garment in flash nd fire exposures. Textile Res J 2004; 74(12): 1033–1040. 2 degree SEC MET SEC MET Burn SE_N (s) SE_C (s) 4. Song G, Gholamreza F and Cao W., Analyzing Fabric Time (s) (Ψ SE_N) (SD) (Ψ SE_C) (SD) Thermal Stored Energy and Effect on Protective (SD) (SD) (SD) Performance, Textile Res J 81: 120-135 (2011). 2.91 0.80 0.69 0.84 0.66 S-1 5. Gholamreza F, Song G, Ackerman M. and Paskaluk S., (0.03) (0.02) (0.05) (0.01) (0.02) 18.12 0.30 13.18 0.31 12.97 Analyzing Thermal Protective Clothing Performance D-1 (0.56) (0.03) (0.66) (0.02) (0.72) upon Hot Liquid Splash, Textile Res J (in press). 33.59 0.19 27.80 0.21 26.68 M-1 6. Gholamreza F, Song G, Ackerman M. and Paskaluk S., (0.78) (0.02) (1.41) (0.02) (0.18) Analyzing the Discharged Energy and its Contribution to Thermal Performance of Protective Clothing upon Hot The lower value of the minimum exposure time for the Liquid Splash, Fiber Society Conference, Switzerland, St. stored energy with compression in comparison with the Gallen, 2012. naturally discharged energy shows that more thermal Thermal and Flame Retardant Behaviors of Cotton Fiber Treated with Phosphoramidate Derivatives

Thach-Mien D. Nguyen, SeChin Chang, and Brian Condon Southern Regional Research Center (SRRC) U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) 1100 Robert E. Lee Blvd., New Orleans, LA 70124 [email protected]; [email protected]

INTRODUCTION Synthesis. The one-step syntheses of high yield have Phosphorus-nitrogen synergism has been recognized in been achieved in high purity, which allow both literatures.1,2 The combination is known to evolve low compounds to be used immediately as the active toxic gases or vapors as well as low evolution of smoke compounds in flame retardant testing without further during combustion and are better in the aspects of purification operations. (Scheme 1). recyclability.3 The reason for the synergistic effect is that phosphorous offers the tendency of char formation, and Scheme 1: Synthesis of EHP and MHP 4 nitrogen forms a protective char during fire. Studies on HO phosphoramidates have also focused on the effect of the O TEA, THF, H N OH O 2 O O H N P P phosphoramidate structure on the flame retardancy of o O Cl 0 C-rt,12h,95% O cellulose.5-8 This research emphasized on the structural EHP effect of two synthesized flame retardants (FRs) HO phosphoramidates, EHP Diethyl 3-hydroxypropylphos O o CCl4,THF,0C-rt O O H O N phoramidate and MHP Dimethyl 3-hydroxypropylphos PH P O H N OH,TEA O phoramidate, on the flame retardant and thermal 2 MHP 12 h, 95 % behaviors of treated cotton fiber.

KEYWORDS: Cotton fiber, Flame retardants, RESULTS AND DISCUSSION Phosphoramidate, Heat of combustion, Mode of action. Synthesis. The phosphorramidates can be easily prepared by Atherton-Todd reaction of phosphites5,9 or elimination APPROACH reaction of chloro-phosphates.10 Due to the availability of General Methods. Both reactions were carried out under the phosphorus substituents in our laboratory, we had nitrogen atmosphere. Chemicals were purchased from chosen to synthesize EHP by elimination reaction and Aldrich and used as received. THF solvent was MHP by Atherton-Todd reaction. purchased from Aldrich and dried using Solvent Purification System from Innovative Technology. NMR Verical flammability and Limiting Oxygen Index spectra were recorded on Varian 400 MHz instrument (LOI) testing. The flammability test shows the 31 using DMSO-d6 as solvent. P is given in δ relative to effectiveness of EHP and MHP as FRs on twill fabric at external 85% aqueous H3PO4. Mercerized cotton twill add-on levels of 10 to 20 wt % as no occurrence of fabric samples were treated with different aqueous afterflame or afterglow burning upon the removal of the solutions of EHP and MHP to achieve different add-ons 5, flame. All MHP samples have shorter char length as 10, 15, and 20 %. Vertical flammability test was compared to EHP samples at the equivalent add-on. From performed on strips of fabric (30 x 7.6 cm) according to Table I, it is obvious that almost all MHP samples achieve ASTM D-6413-11. LOI tests were conducted using strips higher LOI values than EHP ones though the burning time of fabric (13 x 6 cm) according to ASTM D2863-09. to 5 cm line of both types are almost the same except for Thermal gravimetric analyses were performed using a TA the 5 w %. In addition, only the 5 wt % add-on of both Instruments Q500 under nitrogen conditions. TGA-FTIR types is classified as slow burning, the rest can be experiment was followed by TGA between 100-500oC considered as self-extinguishing.11 and Bruker Tensor-27 FTIR at 4 cm−1 resolution in the 800–4000 cm−1 region. Functional groups on the control Thermal degradation. All MHP samples have higher twill and treated fabrics before thermal degradation were char residue (Table I). The two FRs themselves examined on a Bruker Platinum Alpha ATR-IR decompose differently since the decomposition of MHP spectrometer, A220/D01. 34 scans at a resolution of 4 turns it to black char and the decomposition of the EHP cm-1 were recorded for each sample between 4000-750 leaves no char behind (Fig. 1). cm-1. The control twill and all treated fabrics were subjected to the FAA Micro Cone Calorimeter (MCC) (by Fire Testing Technology Limited) and their total heat release (THR) was determined. Fig 1: Char residue images of EHP and MHP at 600oC in TGA pans (compared against the control). Table I: Total heat release (MCC), char residue at 600oC (TGA), and average LOI (%) of control twill and treated Clean pan EHP MHP fabrics.

THR Char residue Average LOI fabric (kJ/g) (%) (%) [std dev] [std dev] (at 600oC) (trials)

Control 8.5 [0.2] 14 18.4 [0.2] (4) Heat of combustion. All treated fabrics have lower THR EHP-5 4.6 [0.2] 31 25.8 [0.5] (4) as compared to the control twill, and all values of MHP EHP-11 5.3 [0.2] 31 31.5 [1.0] (4) samples are lower than those of EHP ones (Table I – 3 EHP-15 6.0 [0.2] 28 31.5 [0.8] (4) observations for each sample). EHP-20 6.3 [0.2] 29 33.4 [0.9] (5)

MHP-5 3.9 [0.5] 33 27.0 [1.5] (4) Evolved gases and functional groups by IR. TGA- MHP-10 3.7 [0.3] 35 29.5 [1.0] (4) FTIR profiles of evolved gases and ATR-IR of functional MHP-14 3.8 [0.3] 36 34.2 [1.2] (6) groups present on the treated fabrics before thermal MHP-19 3.8 [0.2] 36 37.2 [1.3] (5) decomposition reveal different decomposition mechanisms between the FRs. CONCLUSION MHP treated fabrics have lower total heat release, higher Possible mode of action of EHP and MHP. Thermal LOI values, shorter char length in flammability test, and decomposition of EHP could begin by an intra-molecule provide higher char residue as compared to EHP ones at nucleophilic attack on the phosphorus atom to form a six- all add-on levels. The difference in the thermal and flame membered ring intermediate followed by a hydrolysis retardant behaviors of the two compounds could be due to (reaction A) or could simply be a nucleophilic attack of the O-alkyl groups. The smaller size of this group in water on the phosphorus atom resulting in the cleavage of MHP helps it be able to form covalent bond with cellulose an OEt group (reaction B) (Scheme 2). By either way, an and promote the cleavage of P-N bond. The resulted acid intermediate is formed and could further be amine could further react with decomposing cellulose to decomposed or react with cellulose during the thermal form char or get volatilized to prevent more burning. decomposition process. MHP might decompose Further study on durable property using Standard thermally by a different mechanism (reaction C). The six- Laboratory Practice for Home Laundering will be carried membered phosphoramidate is attacked by OH-cellulose out and data will be presented in future paper. as the nitrogen could be protonated to make the ring susceptible to the opening and the OMe group is less ACKNOWLEDGMENT hindrance. The covalent bond is formed between MHP We thank the U.S. Department of Agriculture for and the cellulose. The resulted amine could further react financial support. The authors especially wish to express with decomposing cellulose or get volatilized to prevent their gratitude to Crista Madison for her assistance in LOI more burning. experiments.

Scheme 2: Proposed mode of action of EHP (a) and MHP REFERENCES (b). 1. Tesoro GC. Textilveredlung. 1967; 2:435. 2. Yang CQ, Qui X. Fire Mater. 2007; 31:67. H O O H O H N cyclization N N 3. Horacek, H. and Grabner, R. Polym. Degrad. Stabil. O O O P P P a) A 1996; 54: 205. O O O HO HO HO 4. Wu CS, Liu YL, Chiu YC, Chiu YS. Polymer Degrad. B hydrolysis EtOH Stab. 2002; 78: 41. O O H O N 5. Gann S, Rupper P, Salimova V, Heuberger M, Rabe S, P OH O O N P H EtOH Vogel F. Polymer Degrad. Stab. 2009; 94:1125. O O is H HO lys O H dro H H hy 6. Nguyen TM, Chang S, Condon B, Graves E, Slopek R, O H O N Yoshioka-Tarver M. Manuscript in preparation. P

HO 7. Pandya HB, Bhagwat MM. Text. Res. J. 1981; 51:5. acidic intermediate 8. Pandya HB, Bhagwat MM. J. Fire Retard. Chem. 1978; 5:86. cyclic phosphoramidate O H O H MeOH O H 9. Georgiev EM, Kaneti J, Troev K, Roundhil DM. J. Am. N N N O cyclization O P P O P Chem. Soc. 1993; 115:10964. b) O C O O HO HO H+ 10. Nguyen TM, Chang S, Condon B, Uchimiya S, Fortier

O Cell-OH O H2 C. Polym. Adv. Technol. 2012. O N P O P O NH 11. Bajaj, P. Handbook of Technical Textiles, Horrocks, Cell-O 2 O protonated phosphoramidate A.R.; Anand, S.C. Eds. Woodhead Publishing, 2000, 223.

Characterization of Component Fibers in Military Textiles Using Pyrolysis-GCMS

Pearl Yip U.S. Army Natick Soldier Research, Development, and Engineering Center, USA [email protected]

High performance fibers including nylon, chromatogram of the individual polymers para aramid (Kevlar and Twaron),meta- [3]. For example, the NYCO fabrics aramid (Nomex), as well as cotton and containing fibers with 50% Cotton and fibers are being applied in military 50% nylon 6,6 will have a pyrolysis textiles for specific applications such as chromatogram or pyrogram containing light weight, comfort, high strength, molecular fragments from both cotton and impact-, chemical-, and/or thermal- nylon 6,6 polymers. The pyrogram, of a resistance. Increased used of powerful material recorded at the same pyrolysis Improvised Explosive Devices or IEDs has temperature and GCMS parameters will become the new battlefield challenge for give the same characteristic “finger print” the soldiers in recent wars in Iraq and of peaks pertained to the material. Afghanistan. Blasts from IEDs are able to generate high heat flux and thus cause more burn injuries on the battlefield. Due to high conjugation of the aromatic chain structure back bone, and linear orientation, para-aramids fibers exhibit higher strength, thermal resistance and impact protection[1 ]. FIGURE 1. Pyrogram of a NYCO fabric which Pyrolysis provides a means to thermally containing 50-50 cotton and nylon 6,6 shows the break up the polymers into smaller, pyrolysis products of cyclopentanone and the volatile fragments in the absence of monomer unit of nylon 6,6, and the levoglucosan fragment from the cotton fiber. oxygen. Analytical pyrolysis has long been used to study polymeric materials by It was interesting to see that PY-GC-MS observing their molecular fragments can differentiate Kevlar and Nomex fibers formed during pyrolysis. A pyrolyzer by their pyrolysis products. Kevlar is the incorporated with a GC-MS allows the para aramid and Nomex is the meta volatile fragments to be separated by the aramid. One would not be able to gas chromatrography column, and differentiate the pyrolytic fragments by subsequently identified by the mass mass alone. Due to the different spectrometer[2]. Many military textiles substitution positions on the fragment yarns are consisted of intimately blended molecules having different polarity and fibers with multiple components. Because structural steric effect, this results in the thermal degradation mechanism of a slightly different retention times in the polymer is largely an intramolecular event, chromatogram for the pyrolysis fragments a pyrolysis chromatogram of a fiber from Kevlar and Nomex fibers. It is noted composed of two polymers would that diamine is a more preferable resemble the superposition of the fragment for Nomex fiber than for Kevlar Therefore one can differentiate the two type of fibers by their pyrogram patterns.

FIGURE 3. Peak intensity of a flame retardant chemical from the FR-rayon was found to increase with increasing temperature from 125 to 200°C. Subsequently, the washed and pre-washed of a FR-textile, FRACU, containing the FR-rayon were tested using the same method. It was found repeatedly that the FIGURE 2. Pyrograms of a three types of Kevlar FR textile after 5 times of laundering (129, 49, and KM2D) on top and two types of cycles showed significantly lower Nomex (N101 and N303) fibers on the bottom concentration of the FR chemical show distinguishable pyrogram patterns and slight change in retention time. compared to the pre-washed FRACU fabric.

Polymeric fibers usually include many non-polymeric components such as flame retardant additives. Thermal desorption technique at low temperature can separate organic additives from the material well before the polymeric fiber reaches pyrolytic conditions [4]. When this type of measurement was performed on a FIGURE 4. The PY-GCMS measurement at flame-retardant (FR) rayon fiber at 200°C, 200°C of fibers taken off the FRACU fabrics it was noticed that the flame retardant before and after 5 laundering cycles repeatedly chemical was the major and the only peak show a marked reduction in intensity of the flame in the pyrogram. Subsequently, the FR- retardant chemical in the fabric after laudering. rayon were measured at 125, 150, 175, and

200 °C. Increasing amount of flame REFERENCES retardant was detected with increased [1] Wilusz, E., Military Textiles, CRC temperature from 125 to 200 °C. It seems Press, 2008. that this flame retardant can be baked off [2] Moldoveanu,S.C., Analytical the rayon fiber by heat lower than 200 °C. Pyrolysis of Synthetic Organic Polymers, Elsevier Inc., 2005. [3] Wampler,T.P., Applied Pyrolysis Handbook, CRC Press, 2007. [4] Wampler, T.P., Zawodny, C.P., Jansson K.D., “Multistep Thermal Characterization of Polymer Using GC- MS,” American Laboratory, 2007.

Mechanical Properties

Developing an Environmentally Friendly Isothermal Bath to Obtain a New Class of High-Performance Fibers

H. Avci, H. J. Yoon, R. Kotek College of Textiles, Textile Engineering Chemistry and Science, North Carolina State University, Raleigh NC 27695-8301, USA [email protected]; [email protected]

OBJECTIVE 11.67±0.91 g/d with the modulus value of 152.36±19.95 Development of new families of high performance g/d. thermoplastic fibers was investigated by utilizing liquid isothermal bath. This novel melt spinning method allows SEM Analysis producing special fibers at relatively high throughputs Figures 1 demonstrates that the fibers have highly ordered from commodity polymers with the cost/performance, structure which transformed into fibrillar crystals by a environment, health, and safety benefits. little hot drawing to show high performance.

INTRODUCTION Understanding the theoretical investigations on the solid mechanism of single crystal growth, degree of orientation in amorphous regions, and precursor for crystallization that give ideas to researchers to produce fibers with a wide range of properties. High performance fibers are very important types of material that are extensively used in industry and our daily applications such as sports and specialty fabrics, cords, electronic packaging, ropes geotextiles, automotives, etc. Figure 1: SEM images of cross section of ‘A’ fibers.

The traditional melt spinning technology is widely X-Ray Analysis accepted and used by industry because of it is simplicity The significant effect of this technology on fiber and without mass transfer or adding chemical crystallinity was observed as seen in Figure 2. This is complexities. Numerous studies show that there is a quite surprising for as-spun fibers in which the fibers strong relationship between the structural development show high tenacity and modulus, and also produced at and spinning conditions during the melt spinning process. high speed spinning method. As-spun filaments do not For example, using a very high degree and rapid exhibit any distinct crystal peaks as control fibers quenching for extruding fiber and then drawing at low (untreated) have crystal peaks. rates with high draw ratios (DR), slow two-stage drawing are some important parameters to manufacture high performance fibers1.

APPROACH A key aspect of this research is the melt-spinning combined with wet spinning2-4 to obtain a highly oriented and noncrystalline precursor before drawing process with using regular MW polymers. After a very low draw ratio (< 1.5x DR) the efficient polymer chain orientation can be achieved with highly crystalline and ordered structure for fibers.

Figure 2: Equatorial X-ray diffraction profiles of ‘A’ type RESULTS AND DISCUSSION as spun fibers. Tensile properties

One of the most attractive mechanical properties of fibers DSC Analysis spun with this technology is their ultra high tenacity and After drawing process (< 1.5x DR), treated fibers showed modulus. Using a commercially well known polymer 8.9 oC higher melting temperature than untreated fibers (Polymer XP) has resulted in 5.99±0.07 g/d tenacity value for second melting peak and 6.88 % higher crystallinity as for as-spun fibers by using this novel method. After a well. Increasing peak temperature and degree of very low draw ratio (< 1.5x DR), the tenacity increased to crystallinity with increasing draw ratio indicates a higher level of molecular ordering.

In addition, the fibers birefringence has improved by ca. 65 % and 44 % for as-spun and drawn fibers when compared with control, untreated, fibers.

CONCLUSIONS This unique technology was successfully incorporated to production line to produce melt-spun high performance filaments. A highly oriented amorphous phase with a very low degree of crystallinity and smaller crystallite size were developed for as-spun fibers. As a result of a hot drawing at low draw ratios, a highly oriented crystalline phase was achieved, which yielded significantly improved fiber properties. Resulted fiber performance is much higher as compared to the maximum tenacity and modulus achieved by any of the existing melt spinning methods.

This study contributes a further understanding of structure development under simple, cost effective, ecologically friendly conditions. In addition, this system demonstrates the capability of manufacturing high performance filaments in industrial scale with smaller production area and much less capital investment than any traditional system.

REFERENCES 1. Lewin M. (2007). Handbook of Fiber Chemistry. Baco Raton, FL: CRC Press. 2007; 3rd Ed. 2. Cuculo J. A. et al. (1992). US patent: US005149480A. Melt spinning of ultra-oriented crystalline polyester filaments. 3. Cuculo J. A. et al. (1998). US patent: US005733653A. Ultra-oriented crystalline filaments and method of making same. 4. Chen, P., Afshari, M., Cuculo, J. A., & Kotek R. (2009). Direct formation and characterization of a unique precursor morphology in the melt- spinning of . Macromolecules, 42, 5437–5441.

The Mechanics and Tribology of Electrospun PA 6(3)T Fiber Mats

Matthew M. Mannarino1 and Gregory C. Rutledge2 1Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 2Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 [email protected]; [email protected]

STATEMENT OF PURPOSE voltage power supply was used to achieve an electrical The mechanical and tribological properties of electrospun potential of 22 kV at the top plate. The nozzle consisted fiber mats are of paramount importance to their utility as of a stainless steel capillary tube (1.6 mm OD, 1.0 mm components in a large number of applications. Although ID) in the center of the top plate. A digitally controlled some mechanical properties of these mats have been syringe pump was used to obtain a flow rate of 0.010 reported previously, investigation of their tribological mL/min. Heat treatment of the electrospun mats was properties is essentially nonexistent. In this work, carried out in a Thermolyne lab oven by draping EFMs electrospun nanofiber mats of poly(trimethyl over a 100 mm diameter pyrex dish and placing it in the hexamethylene terephthalamide) (PA 6(3)T) are oven for 2 hours at a specified temperature. characterized mechanically and tribologically.

INTRODUCTION Electrospinning offers a particularly simple and robust method to create polymeric nanofibers of various morphologies and sizes, inexpensively and in large quantities. In electrospinning, a viscoelastic fluid is charged so that a liquid jet is ejected from the surface of the fluid (supplied by a needle or spinneret) and accelerated by an electric field towards a grounded collector, thus creating an electrospun fiber mat (EFM). Modification of the fiber diameter, porosity, surface area and mechanical properties of the mat, by adjusting the processing conditions and solution parameters, can be used to tailor EFMs for various applications. Post-spin treatments can improve the mechanical strength and expand the utility of EFMs; however, the resistance of Figure 1. SEM Micrographs of PA 6(3)T nanofibers after electrospun mats to wear remains a significant issue. In varying degrees of heat treatment. From upper left to order to improve the robustness of EFMs, both lower right: untreated, and 2 hours thermal annealing at mechanical strengthening and tribological tailoring is 130, 150, and 170 °C. Scale bar for each image is 1 µm. required to keep the mats intact. Quantitative evaluation of the wear resistance of nanofiber mats is critical for a Mechanical Testing better understanding the underlying mechanism of wear Uniaxial tensile testing of EFMs was measured with a occurring in EFMs. This work seeks to quantify the Zwick Roell Z2.5 tensile testing machine using a 2.5 kN tribology of nanofiber mats, and to demonstrate the load cell. Rectangular specimens were cut to 100 mm  improvement of mechanical integrity and wear resistance 12.5 mm and extended at a constant crosshead speed of of EFMs by post-spinning thermal treatments [1]. 0.50 mm/s with a 50 mm gauge length.

APPROACH Tribological Testing Materials The abrasive wear resistance of the electrospun mats was Poly(trimethyl hexamethylene terephthalamide) (PA measured by subjecting the mats to a modified ASTM D- 6(3)T) was purchased from Scientific Polymer Products, 3884-09 [Standard Test Method for Abrasion Resistance Inc. It is an aromatic, amorphous polyamide with a high of Textile Fabrics (Rotary Platform, Double-Head glass transition temperature (Tg=425 K) and outstanding Method)]. Test samples were prepared by carefully mechanical properties. The solvent used, N,N-dimethyl cutting out 100 mm diameter circles from an EFM and formamide (DMF) was purchased from Sigma-Aldrich attaching them to the adhesive side of a 100 mm diameter and used as received for creating polymeric solutions. Polyken® 339 duct closure foil. For comparison, a solution cast film was made by depositing 3.0 mL of 20 Electrospinning of Nanofiber Mats wt.% PA 6(3)T in DMF on a 100 mm diameter ® Nanofiber mats were fabricated by electrospinning from sheet and allowing the solvent to evaporate overnight in a organic polymer solutions using a parallel plate geometry fume hood. H-38 Calibrade® standardized abrasion testing consisting of two aluminum plates, each 12 cm in wheels were used with an applied load of 25 or 100 g for diameter, with a tip-to-collector distance of 25 cm. A high 10, 50, 100, 250, 500, and 1000 cycles at 240 mm/s. RESULTS AND DISCUSSION stress and yield strain of the nonwoven mats; therefore, The Young’s modulus of the PA 6(3)T EFMs increased we propose a modified version of the Ratner-Lancaster significantly from 40 MPa for the untreated mat, to 82 relationship in which the yield stress, σy, and yield strain, MPa and 117 MPa after 130 °C and 150 °C heat- εy, of the mat replace the breaking stress and breaking treatment, respectively, without suffering a significant strain of the fibers. The wear rate is furthermore put on a loss of porosity; the modulus could be increased further to mass basis by the bulk density of PA 6(3)T, ρ, to get: >400 MPa after 170 °C heat-treatment, but at a substantial W~(ρµL)/(σyεy). Figure 2 compares the effective wear loss to the mat porosity (88% to 63%). The mechanism of rates of the treated nanofiber mats to the modified Ratner- wear for EFMs can be due to physicochemical Lancaster wear rate relationship and confirms that there is interactions, asperity interactions, or macroscopic a strong correlation between the wear rate and the -1 deformation. All of the electrospun mat samples used in quantity (σyεy) for both the 25 g and 100 g applied loads. this work consist of identical chemical composition, similar fibrous morphology, and comparable surface CONCLUSIONS roughness; therefore, differences in the abrasive wear for The tribological and mechanical response of thermally these EFMs is most likely due to macroscopic treated EFMs was investigated in this work. The Young’s deformation caused by exceeding the yield stress of the moduli and yield stresses of the mats were found to mats. In the abrasive wear of polymers, deformation of a improve dramatically with an increase in the temperature surface is generally a function of the indentation hardness, of heat-treatment near the glass transition, at the expense the relative motion opposed by the frictional force, and of mat porosity. The effective wear rate of nanofiber mats disruption of material at the contact points, involving an was well-described by a modified Ratner-Lancaster amount of work equal to the area under the stress-strain relationship for wear rate of polymeric materials, curve. These three processes occur sequentially; therefore, W~(ρµL)/(σyεy), suggesting that the mechanism of wear is the total wear should be proportional to a product of the primarily due to the breakage of fibers that is also hardness, the frictional force, and the work (energy) of responsible for yield in these nonwoven mats. Post-spin material removal. One of the most commonly used treatments such as thermal annealing close to the relevant relationships based on this mechanism is the Ratner- thermal transition temperature (Tg) serve to weld the Lancaster correlation [2], which predicts the wear rate as: fibers to form additional fiber junctions, significantly W=C(µL)/(Hσbεb), where C is a constant, µ is the improving the mechanical and tribological properties of coefficient of friction, L is the applied load, H is the the electrospun mats and greatly improving their utility. hardness, σb is the breaking stress, and εb is the breaking strain. This relationship includes a term for the FUTURE WORK indentation hardness; however, for most polymers the We expect to continue our investigation of the mechanical dominant parameters are σb & εb [3,4]. and tribological properties of electrospun fiber mats by evaluating the response of a semi-crystalline polymer (polyamide 6,6) EFM to abrasive wear cycling as a function of the degree of crystallinity.

KEYWORDS Electrospinning, Nanofiber, Wear.

ACKNOWLEDGMENTS Funding for this work was provided by the National Science Foundation through grant number CMMI- 0700414, the Masdar Institute, and the U.S. Army through the Institute for Soldier Nanotechnologies (ISN) under AROW911NF-07-D-0004. The authors would like to thank Prof. Stephen Burke Driscoll and the Plastics Engineering Department at the University of Massachusetts Lowell for use of their Taber abraser. The authors would also like to acknowledge the MIT Institute for Soldier Nanotechnologies for use of facilities.

Figure 2. Effective wear rate vs. (ρµL)/(σyεy) of EFMs REFERENCES subjected to varying temperatures of thermal treatment: [1] Mannarino M.M., G.C. Rutledge, Polymer 2012; (◆) 25 g applied load, ( ) 100 g applied load wear. The 53(14):3017-3025. line with slope=1 is drawn as a guide to the eye. [2] Lancaster J.K., Wear 1969;14(4):223-239. [3] Wang A. et al., Wear 1995;181:241-249. For EFMs, we suggest that the breaking stress and [4] Shipway P.H., N.K. Ngao, Wear 2003;255:742-750. breaking strain of individual fibers is reflected in the yield

On the Design Method of Lightweight Construction Materials: Structural Characteristics-Tearing Strength Relationship

Fatih Suvari1, Yusuf Ulcay1,2 1Uludag University, Faculty of Engineering and Architecture, Textile Engineering Dept., Bursa, Turkey 2Bursa Technical University, Bursa, Turkey [email protected]; [email protected]

INTRODUCTION few synthetic polymers that has found wide industrial Composite materials that consist of fabric and coating application [1]. PVC has good oil, solvent and polymer have been used for lightweight construction abrasion resistance, and unique ability to be applications. These materials can be used in long compounded with additives [1] [2]. PVC is also distances to cover places like stadiums, train stations, popular for its low cost and processability by a wide airports etc. without need of supports. Lightweight variety of techniques [1]. Acrylic treatment was made construction materials are usually subjected to to one of the samples. Acrylic is known to have good tension and tear can propagate rapidly under stress, resistance to UV light and ozone [1] [2]. All the damaging the material and leading to its failure [1]. If materials tested in this study were coated by knife there is a desire to design long life lightweight coating method. Some basic properties of selected construction structures, these materials should have materials were given in Table I. good tear strength and resistance to tear propagation. Testing Methods Structural parameters like construction of the fabric, There are a number of tear tests such as single rip, yarn fineness, yarn density (yarn per cm), coating wing tear and Elmendorf tear [2]. We used single rip polymer are important, because they determine (tongue) procedure and constant rate of extension tearing property of the material. tensile testing machine for measuring tearing properties of the materials. Specimens were tested in The aim of this work is to give relationship between accordance to ASTM D2261-11, except specimen some structural characteristics and tearing strength of dimensions. Specimens of 100 mm x 35 mm were lightweight construction materials like coated taken from materials. As a preparation for tearing textiles. We believe that, results may be useful in test, specimens were cut from X to Y (45 mm) as designing these materials with optimum tearing shown in Figure 1. strength.

EXPERIMENTAL Material Woven, knitted, or nonwoven textiles can be used as base materials for coated fabrics. In this work, commercial coated textile materials with warp knitted mesh fabric were selected for testing. Warp knitted fabrics as base materials are relatively less elastic and dimensionally more stable than their counterparts. All Figure 1: Specimen dimensions for tearing test the textile fabric/substrate used for coating is made of polyester fibers. Since polyester fiber has lower RESULTS AND DISCUSSION elongation and higher modulus relatively, it can be Choosing suitable textile substrate (base material) advantageous in terms of mechanical properties. construction parameters for coating is important, Polyvinyl chloride (PVC) was used as a coating because they offer the primary tearing properties to polymer for all coated samples. PVC is one of the the product.

Table I: Description of the coated textile materials Yarn density Basis weight Material Yarn fineness [tex] Fiber type Coating polymer [Yarn/inch] [g/m2] S1 55 x 55 9 x 9 Polyester 240 None S2 110 x 110 9 x 9 Polyester 270 None A 110 x 110 18 x 18 Polyester 680 Polyvinyl chloride (PVC) B 110 x 110 20 x 20 Polyester 620 Polyvinyl chloride (PVC) C 110 x 110 25 x 25 Polyester 1100 PVC + Acrylic D 93 x 93 20 x 20 Polyester 900 PVC + PVDF In Figure 2, tearing behaviors of two different textile Lower tearing strength results from material A and B can substrates are given. The only constructional difference be expected than material S2, since they have polymer between these two uncoated base fabrics is yarn fineness. coating. However, it is clear from Figure 3 that tearing The fabric with code S2 is constituted of thicker yarns. strengths of the material A and B are higher than the textile substrate (S2). We think polymer coatings of material A and B did not show enough resistance to possible yarn movement during tearing.

Tearing test results of material B and C, and D are given in Figure 4. Material C and D have extra acrylic and PVDF treatment, respectively. See Table I for other constructional differences.

Figure 2: Tearing behaviors of textile substrates

The maximum forces that fabrics stand without tearing for S1 and S2 are 44.2 N and 53.7 N, respectively. Moreover, the fabric with thicker yarns (S2) has higher peaks along the propagation distance (Figure 2). This indicates that S2 is more resistive to tearing. Note that basis weight increased from 240 to 270 g/m2 with using thicker yarns. Figure 4: Tearing test results of material B, C, and D Tearing behaviors of two PVC coated textile materials (A The material C showed less resistance to tearing force and B), and a textile substrate (S2) are given in Figure 3. The only constructional difference between PVC coated according to Figure 4. We think extra acrylic treatment textiles is yarn density [yarn/inch] that material has. The probably helped to block possible yarn movement of the material with code B has more yarn per inch (see Table I). base structure. The same situation may have occurred for material D, since it has an extra PVDF treatment.

CONCLUSION Textile substrate with thicker yarns showed more resistance to tearing force. However, using thicker yarns in base fabric makes final product heavier. Heavy material needs more support in lightweight construction applications. PVC coated textile materials having fewer yarns per inch showed more resistance to tearing. Therefore, designing base fabrics with fewer yarns per inch can be advantageous in terms of tearing strength. PVC coated fabric showed more resistance to tearing force. We think PVC coating can hardly hold the yarns against tearing force. Although extra acrylic and PVDF treatments add extra specialties to material, they may Figure 3 Tearing behaviors of A, B, and S2 materials affect tearing properties of the coated materials The maximum forces that materials stand without tearing negatively. for A and B are 270 N and 225 N, respectively. Note however, that the material A has only one major peak REFERENCES (Figure 3). We think this major peak is related to mobility 1. A. K. Sen, Coated Textiles Principles and of the yarns. Since the material A has fewer yarns per Applications, Technomic Publishing Co. Inc., inch, some of the yarns vertical to the tearing propagation USA, 2001, ISBN:1-58716-023-4. direction may get closer easier during tearing. These 2. W. Fung, Coated and Laminated Textiles, yarns probably showed resistance together to tearing force Woodhead Publishing Limited, England, 2002, at that major peak. It should be noted that however, the ISBN: 1 85573 576 8. material with fewer yarns per inch would be weaker in terms of tensile strength. Continuous Dynamic Analysis: Evolution of Storage and Loss Modulus in Fibers as a Function of Strain

Sandip Basu and Jennifer Hay Agilent Technologies, Chandler, AZ, USA [email protected], [email protected]

Understanding the mechanical behavior of fibers is called Continuous Dynamic Analysis (CDA), where a important for their applications in biomedical, textile and small harmonic force is superimposed on top of the quasi- composite materials technologies. This is especially true static force. The CDA enables us to measure the storage for very small-diameter fibers (nano- and micro-fibers), and loss modulus of thin fibers as a continuous function where the properties can be significantly different from of strain. The results on thin fibers of semi-crystalline their bulk counterparts. Characterization of small- polymers, such as polypropylene and polyester, exhibit a diameter fibers in tension is a challenging problem due to dramatic increase in dynamic storage modulus with strain their fine diameter and high compliance. In this work, we due to increasing alignment of the amorphous molecules used a novel dynamic tensile testing instrument (please with the crystalline regions (Fig. 2a). This, in turn, also see schematic in Fig. 1), with high force and displacement causes a significant decrease in the dynamic loss factor of resolution, to characterize tensile behavior of various the fibers (Fig. 2b). fibers with diameters of the order of a few microns. 1200 45

Engineering Stress 40 Crosshead driven at 1000 35 specified strain rate Storage Modulus

with 35 nm extension (MPa) 800 30 (GPa)

resolution 25 Stress 600 Modulus

20

400 15 Storage Engineering 10 200 Fiber Specimen 5

0 0 a 0 0.05 0.1 0.15 0.2 0.25 Engineering Strain (mm/mm) 6000 0.12

5000 Loss Modulus 0.1 Loss Factor 4000 0.08 (MPa)

Nanomechanical

3000 0.06 Factor Actuating Modulus Loss Transducer 2000 0.04 Loss

1000 0.02 Figure 1. The nanomechanical actuating transducer (NMAT) enables detection of small loads required for 0 0 deformation of small diameter individual fibers. b 0 0.05 0.1 0.15 0.2 0.25 Engineering Strain (mm/mm) When a polymer fiber is stretched axially, the molecules Figure 2. Continuous dynamic analysis of PET fiber tend to align themselves along the tensile axis, and this during tensile test. (a) Variation in engineering stress and realignment modifies the elastic properties of the fiber. storage modulus; and, (b) Variation in loss modulus and However, the evolution of these properties cannot be loss factor as a function of strain. quantified from conventional quasi-static tensile tests. In this presentation we demonstrate a novel test method,

Natural Fibers

Soybean Biorefinery Model: Nanofibers, Nanocomposites, Green Composites and More

Anil N. Netravali Cornell University [email protected]

ABSTRACT thermal properties. Together, natural plant based cellulose This paper discusses how the biorefinery model can be fibers such as sisal, ramie, kenaf, jute, flax, henequen, applied to soybean plant to fully utilize all parts of the hemp, etc. and protein and starch based resins can form plant. The protein from soybeans can be used to produce composites with moderate mechanical properties [4-6]. In resins to fabricate green composites with strengths up to reality, such composites can be engineered to have the range of advanced composites. The protein may also properties better than wood and wood products such as be used to produce nanofibers for filtration. The sugars particle board, medium density fiber boards and plywood. (carbohydrates) can be used to obtain bacterial cellulose However, recent development in spinning liquid nanofibers for a variety of applications. The oil can be crystalline (LC) cellulose fibers with significantly higher modified for epoxy or polyurethane resins. Micro- and strengths allows the possibility to create ‘Advanced green nano-fibrillated cellulose (MFC/NFC) extracted from Composites’ for structural applications [7,8]. plant stems can be used as reinforcing agent for the resins. The remaining parts of the plants can be pelletized and The purified protein can be electrospun into nanofibers burned for heat. A schematic of the soybean biorefinery for applications in air filtration. Besides being green and model is presented in Figure 1. As it can be seen from biodegradable, some of the amino acids in soy protein Fig. 1 each part of the plant can be used effectively. carry charge and attract the particles as small as 80 nm. Such filters are capable of attaining high filtration efficiency.

The defatted soy flour (SF) purification process essentially consists of removing the soluble sugars (fructose, glucose, sucrose, raffinose and stachyose) and thus increasing the protein content. The blend of sugars can be used to carry the fermentation process using Acetobacter xylinum which secrete bacterial cellulose (BC). BC has the same chemical structure as other plant- based cellulose and is produced as fibers with diameters in the range of 70–90 nm [9]. BC has been used in many applications from composites to speaker diaphragms and from blood vessels to high quality paper [10-12].

Part of the SF that cannot be used for the applications mentioned above can be used with other additives

including fibers derived from plant stems for use as Figure 1: A schematic of the soybean biorefinery model hydromulch.

INTRODUCTION PROCESSING, RESULTS, AND DISCUSSION Most polymers, fibers and composites used today are Composites derived from petroleum. Most of them are non-degradable Green composites have been made using soy protein (SP) and pollute land, water and air if discarded without proper based resins and plant fibers [4-7]. The SP resin process is care. Since fiber reinforced composites are not easy to simple and water based. The resin can be impregnated in reuse or recycle, over 90% are discarded into landfills at any form of natural fibers (fabrics, nonwovens). The the end of their life [1,2]. It is, however, possible to derive prepregs can be layered and hot pressed to obtain many fibers, and resins from sustainable, plant based composites. The composites, thus, can be engineered to sources [2,3]. At the end of their life, rather than dumping obtain desired mechanical properties. them in landfills they can be simply composted. Plants Fracture strengths of unidirectional green composites produce cellulose, proteins and starches in abundance. made using flax yarns were above 250 MPa while the While cellulose is mostly available in the fiber form and Young’s modulus was over 3.7 GPa [4]. In another set of can be used as reinforcing component, proteins and unidirectional composites made using ramie fibers, the starches that do not have linear conformation can be used fracture strength and Young’s modulus values were 270 as resins after proper modifications including crosslinking MPa and 4.9 GPa, respectively [5,6]. Such composites and nanoadditives to improve their mechanical and can be used in place of wood, medium density fiber CONCLUSIONS boards, plywood and particle boards. While only a part of the research has been shown in this paper it is clear that the biorefinery model makes it Advanced green composites have been fabricated using possible to use the plants in an efficient way. In this the LC cellulose fibers which have strengths up to 2 GPa. model each part of the plant is used and yields useful They also have much higher fracture strains (10-11%) ® products and hence can be used beneficially. At the end of compared to Kevlar fibers and hence are very tough. their life, these products can be safely discarded or Unidirectional composites made using LC cellulose fibers composted [14-16]. Significant amount of current and SP resins showed strengths of over 650 MPa for research is in this area and many products are anticipated composites that had only 44% LC cellulose fibers ® to hit the market in the near future. compared to just over 1100 MPa for Kevlar based composites [7]. However, their toughness was about 50% ACKNOWLEDGMENT higher than Kevlar® based composites. These advanced The author would like to acknowledge the financial green composites may be used for ballistic applications support from various sources including NSF, NTC, such as for armored vehicles. NYSERDA, Nissan Motor Co., Wallace Foundation, Axium Nanofibers, Hatch (USDA) and the College of Protein nanofibers Human Ecology. Purified SF with about 67% protein content have been electrospun by blending with other water soluble REFERENCES polymers such as PVA in the form of nanofibers onto 1) Stevens, E. S., Green Plastics, Princeton University suitable substrates to form nanofilters [13]. Only a small Press, Princeton, 2002. amount of nanofibers are needed to obtain the desired 2) Netravali, A. N. and Chabba, S., Materials Today, pp. pore size distribution and achieve very high filtration 22-29, April 2003. efficiency. A filter before and after the bacterial filtration 3) Netravali, A. N., Biodegradable test is shown in Figure 2. Composites, Chapter in Biodegradable and Sustainable Fibers, pp. 271-309, R. S. Blackburn, Ed., Woodhead Publishing Limited, Cambridge, UK, 2005. 4) Chabba, S. C., Matthews, G. T. and Netravali, A. N., Green Chemistry, 7, 581 (2005). 5) Nam S. and Netravali, A. N., Fibers and Polymers, 7(4), 388, (2006). 6) Lodha, P. and Netravali, A. N., Composites Science and Technology, 65(7-8), 1225 (2005). Figure 2: Nanofilter; a) before and b) after filtration test 7) Netravali, A. N., Huang, X. and Mizuta, K., From Fig. 2 it is clear that most of the bacteria are Advanced Composite Materials, 16, 282, (2007). attached to the fibers. This is perhaps because of the 8) Borstoel, H., Liquid crystalline solutions of celulose natural charge carried by some of the amino acids in SP. in phosphoric acid, PhD Thesis, Rijksuniversiteit, Groningen, The Netherlands (1998). Bacterial cellulose 9) Qiu, K. and Netravali, A. N., J Mater. Sci., 2012. The sugars obtained from the SF purification can be used DOI: 10.1007/s10853-012-6517-9. as carbon source to obtain BC. The production process 10) Iguchi, M., Yamanaka, S., Budhiono, A. J Mater Sci, using Acetobacter gives BC in the form of pellicles. The 35(2), 261, (2000). pellicles may be dried to form membranes. Such doi:10.1023/A:1004775229149. membranes have been used in many applications. 11) Baeckdahl, H., Helenius, G., Bodin, A., Nannmark, However, they can be immersed in resins to obtain resin U., Johansson, B. R., Risberg, B. and Gatenholm, P., impregnation. Since the BC production process is water Biomaterials 27(9), 2141, (2006). based, water soluble resins such as soy protein, starches, 12) Fink, H.P., Weigel, P. and Purz, H. J., Ganster J PVA, etc. work the best. Qiu and Netravali made BC- (2001) Prog Polym Sci, 26(9), 1473, (2001). PVA composites where PVA was crossliked and BC 13) Cho, D. H., Nnadi, O., Netravali, A. N. and Joo, Y. nanofibers were randomly organized as obtained [9]. The L. Macromolecular Materials & Engineering, 295 (8), Young’s modulus of these composites was as high as 2.5 763-773, (2010). GPa and fracture strength was in the range of 45 MPa. 14) Luo, S. and Netravali, A. N., Polymer Degradation These composites are fully biodegradable. and Stability, 80(1), 66 (2003). Other products 15) Lodha, P. and Netravali, A. N., Polymer Degradation The waste protein that cannot be used in applications and Stability, 87(3), 477, (2005). mentioned above may be used for hydromulches, seed 16) Cho, D. W., Netravali, A. N. and Joo, Y. L., Polymer coatings etc. The plant stems contain cellulose fibers Degradation and Stability, 2012. which can be sheared to obtain MFC/NFC that can be DOI:10.1016/j.polymdegradstab.2012.02.007 used to reinforce resins and plastics. What cannot be used may be pelletized and burned to obtain heat. Self-Assembled Nanostructures from Cellulose Nanocrystals

You-Lo Hsieh University of California, Davis, CA 95616, USA [email protected]

Cellulose is synthesized by many organisms, such Chemical reactivity of the primary (C6) and as plants, marine animals, fungi, and bacteria, etc secondary (C2, C3) hydroxyl groups in cellulose as an important structural component. As the most and the C3 and C6 hydroxyls and C2 acetal amine abundant polymer on the planet, cellulose has long groups of chitin offer opportunities for chemical been a major source of materials. Cellulose is modification to impart significant improvement in chemically unique among natural polymers in that solubility and thermal behavior, thus enhanced it has the highest uniformity and regularity, both processibility, to afford efficient electrospinning chemically and structurally, unlike other from various aqueous and organic solutions.3-7 The polysaccharides (chitin, starch, alginate, etc), chemical and structural potential of these proteins and polyphenolics, etc. Cellulose is a biopolymers has been exploited by coupling homopolymer consisting of -1,4-D(+)- chemistry and polymer physics principles in glucopyranose building blocks in long chain electrospinning to reduce fiber sizes to nanometer lengths. Its extensively inter- and intra-molecular ranges, to create novel morphology, and to alter hydrogen bonded structure further contributes to surface chemistry. Examples include hybrid and the highly rigid and crystalline characteristics. multi-component fibers of sheath-core, nano-

OH OH OH OH porous structure and multiple stimuli-responsive O O HO HO O HO OH O O hydrogel and enzyme bound fibers. HO O HO O OH OH OH n OH CNCs prepared from different biomass are ultra- The naturally crystalline structure of native high modulus and low thermal coefficient cellulose from various sources is also structurally nanomaterials that can be incorporated into unique in that the native nanocrystalline domains nanofibers to create new chemical functionality can be isolated into the so-called cellulose and nano-structured fibrous materials. Cellulose nanocrystals or cellulose nanowhiskers. nanocrystals are 10-50 nm in diameters and 200- Furthermore, cellulose nanocrystals have 400 nm in lengths have been prepared by acid extraordinary bending strength and modulus, hydrolysis and freeze-drying.8-11 These cellulose estimated to be ~10 GPa and 150 GPa1, nanocrystals have highly Iβ crystalline structure respectively, that are comparable in magnitude to with sharper (200) crystal lattice (2θ=22.6°) and (1 those of carbon nanotubes, as well as low thermal expansion coefficient of 10-7 K-1 in the axial 10) planes (2θ=14.7°) and much smaller direction2. mesopores (91.99 ± 2.57 Å) than the micropores (214.64 ± 7.23 Å) in the original cellulose. The BET surface area of these cellulose nanocrystals is Cellulose is readily available, not only from wood 2 and fiber crops, but also from by-products or 13.362 m /g, ~10 times of the original. wastes of agriculture and other processing Recent and on-going work on deriving CNC and industries. The latter makes it particular attractive 7,8 as the major renewable sources for a great variety cellulose nanofibers from various plant sources of chemical feedstock and materials, including (TEM, top next page) and their ability to self- engineered nano-materials. assemble into ultra-fine fibers (SEM, middle next page) and other porous materials (AFM, bottom This paper presents the approaches we have next page) will be presented. developed and are working on to prepare nanofibers and nanofibrous structures from The super high specific surface and hydroxyl cellulose nanocrystals. functionality can utilized to generate CNC based nanocomposites. These new nanofibrous membranes have potential applications in areas such as catalysis, super-hydrophobic surfaces, dye- sensitized solar cells, separation, super- REFERENCES hydrophobic surfaces, sensors, drug-delivery and 1. Iwamoto, S.; Kai, W. H.; Isogai, A.; Iwata, T., medical diagnosis, etc. Elastic Modulus of Single Cellulose Microfibrils from Tunicate Measured by Atomic Force Microscopy. Biomacromolecules 2009, 10, (9), 2571-2576. 2. 4. Nishino, T.; Matsuda, I.; Hirao, K., All- cellulose composite. Macromolecules 2004, 37, (20), 7683-7687. 3. Liu, H. and Y.-L. Hsieh, Ultra-fine Fibrous Cellulose membranes from electrospinning of cellulose acetate, Journal of Polymer Science, Polymer Physics, 40(18):2119-2129 (2002). 4. Zhang, L. and Y.-L. Hsieh, Cellulose Acetate Based Ultrafine Bicomponent Fibers with Nanoscale Structural Features, Journal of Nanoscience and Nanotechnology 8, 4461- 4469 (2008). 5. Du, J. and Y.-L. Hsieh, Nanofibrorus membranes from aqueous electrospinning of carboxymethyl chitosan, Nanotechnology 19, 571-579 (2008). 6. Du, J. and Y.-L. Hsieh, Cellulose-chitosan nanofibers from electrospinning of their ester derivatives, Cellulose 16(2): 247-260 (2009). 7. Ding, B., J. Du, and Y.-L. Hsieh, Layer-by- layer self-assembled polysaccharide electrolytes on cellulose nanofiber, Journal Applied Polymer Science, 121: 2526-2534 (2011). 8. Lu, P. and Y.-L. Hsieh, Preparation and properties of cellulose nanocrystals: rods, spheres, and network, Carbohydrate Polymers 82, 329–336 (2010). 9. Lu, P. and Y.-L. Hsieh, Cellulose nanocrystal filled poly(acrylic acid) nanocomposite fibrous membranes, Nanotechnology 20: 415604- 415612 (2009). 10. Lu, P. and Y.-L. Hsieh, Preparation and characterization of cellulose nanocrystals from rice straw, Carbohydrate Polymers, 87:564- 573 (2012). 11. Lu, P., Y.-L. Hsieh, Cellulose isolation and core-shell nanostructures of cellulose nanocrystals from chardonnay grape skins, Carbohydrate Polymers, 87:2546-2553 (2012).

ACKNOWLEDGMENT Funding from the California Rice Research Board, USDA NIFA and National Textile Center.

Findings from research conducted by P. Lu and F. Jiang as well as prior work by J. Du and H. Liu, B. Ding and L. Zhang. Orientation of Cellulose Nanofibers Using Magnetic Fields and Wet-Stretching

Stephen J. Eichhorn1, Arthur Wilkinson2, Tanittha Pullawan2 1College of Engineering, Maths & Physical Sciences, University of Exeter, Exeter, Devon, UK 2School of Materials, University of Manchester, Manchester, UK [email protected]

STATEMENT OF PURPOSE/OBJECTIVE microcrystalline cellulose and N,N – dimethyl acetamide The purpose of the following work is to – DMAc) and cured both in the presence and without a  Align cellulose nanofibers using magnetic fields magnetic field (1.5 T). The mechanical properties of these and wet stretching composite materials were determined using tensile  Show how this alignment of nanofibers leads to testing. Samples were also initially wetted prior to an enhancement of local stiffness in a composite deformation to see the effect of moisture on their material mechanical properties. Detailed micromechanics of the  Better understand the driving forces of materials, including molecular deformation and CNW orientation of nanofibers and how mechanical orientation, were obtained using Raman spectroscopy. properties might be best optimized. These experiments were also performed in wet and dry states. Samples were deformed in tension and the shift in INTRODUCTION bands located at 1095 cm-1 and 895 cm-1 were In recent times cellulose nanofibers and nanocomposites followed; these bands are representative of the have attracted an enormous interest, both in the academic CNWs/matrix and matrix components respectively.20 community1-4 and as potential industrially exploited technology. Given this high level of interest and potential RESULTS AND DISCUSSION for commercialization, it is important that we fully When the composites were cured in the presence of the understand possible ways in which we might process magnetic field, the CNWs were observed to align. This these materials on an industrial scale. Processing of alignment takes place perpendicular to the magnetic field, conventional short fiber composites involves pressing and due to the diamagnetic susceptibility of the CNWs being extrusion of the fibers and surrounding matrix. During greatest along their chiral axis (perpendicular to the main this processing, orientation of the fiber component occurs. axis of the CNWs). This alignment is found not to be This orientation leads to anisotropic stiffness complete, with the composite microstructure comprising enhancement of the resulting composite. oriented and randomly oriented domains of CNWs. Orientation of the CNWs, due to the presence of the Cellulose is the most utilized and readily available 5 magnetic field, leads to an enhancement of both modulus polymeric material on the planet. It is mainly found in and strength of the composites. Pronounced changes in the cell walls of plants, but can also be produced by the intensity of the band located at 1095 cm-1 indicates bacteria and certain animals (tunicates). Cellulose is that the CNWs are indeed oriented in the domains. Little typically a semicrystalline polymer, with a significant change in the intensity of the band located at 895 cm-1 amorphous fraction. Controlled acid hydrolysis of suggests that no orientation of the cellulose molecules in cellulose has shown that it is possible to extract the the matrix material occurs in the presence of the magnetic crystalline fraction to form rod-like whiskers (called field. During deformation, the position of the band located cellulose nanowhiskers – CNWs) with nanoscale -1 6,7 at 1095 cm is found to shift towards a lower dimensions. Cellulose nanfibers have been oriented 8-10 wavenumber position (see Figure 1). Greater shift rates, using magnetic fields , conventional wet spinning 11 12-14 15 with respect to strain, are found for samples that are processes , electric fields , pressing and casting , 16 deformed perpendicular to the direction of the applied coffee ring drying and by locking in a liquid crystalline 17 magnetic field, reflecting the coincidence of the nematic ordering. In the present work we report the orientation of the CNWs with the tensile direction. It is orientation of CNWs in an all-cellulose composite also shown that lowering the volume fraction of CNWs in structure, both using a low power magnetic field and wet the composites assists the orientation process in the stretching. All-cellulose composites comprise a cellulose 18 magnetic field by allowing greater “freedom” for rotation. fiber reinforcing a cellulose matrix material. During deformation of the samples in the wet state, little APPROACH orientation of the CNWs or the molecules occurs. It is CNWs were prepared by acid hydrolysis of tunicates and shown that for orientation of these components to occur, cotton using sulphuric acid. The details of this processing the samples must be dry. route can be found elsewhere.19 These CNWs were then combined with a dissolved cellulose matrix (comprising CONCLUSIONS (10) Kvien, I.; Oksman, K. Appl. Phys. A-Mater. Sci. CNWs have been shown to orient in a magnetic field Process. 2007, 87, 641. during the curing of an all-cellulose nanocomposite. (11) Iwamoto, S.; Isogai, A.; Iwata, T. Orientation of the CNWs also occurs during dry Biomacromolecules 2011, 12, 831. stretching of the same material. It is shown that the (12) Bordel, D.; Putaux, J. L.; Heux, L. Langmuir 2006, mechanical properties (strength, stiffness) increase when 22, 4899. the magnetic field is applied, and when the CNWs orient (13) Csoka, L.; Hoeger, I. C.; Peralta, P.; Peszlen, I.; during stretching. These approaches could be useful for Rojas, O. J. Journal of colloid and interface science enhancing the stiffness of cellulose fibers and films. 2011, 363, 206. (14) Gindl, W.; Emsenhuber, G.; Maier, G.; Keckes, J. Deformed parallel to magnetic field 0.0 Deformed perpendicular to magnetic field Biomacromolecules 2009, 10, 1315. Deformed - no magnetic field -1 -1 2 (15) Rusli, R.; Shanmuganathan, K.; Rowan, S. J.; -0.5 Gradient = -0.38 cm % ,R = 0.93 Weder, C.; Eichhorn, S. J. Biomacromolecules 2010, )

-1 11, 762. -1.0 (16) Uetani, K.; Yano, H. ACS Macro Letters 2012, 1, Gradient = -0.7 cm-1%-1 2 651. -1.5 ,R = 0.98 (17) Tatsumi, M.; Teramoto, Y.; Nishio, Y.

Raman shift (cm Biomacromolecules 2012. -2.0 (18) Huber, T.; Mussig, J.; Curnow, O.; Pang, S. S.;

-1 -1 2 Bickerton, S.; Staiger, M. P. Journal of Materials -2.5 Gradient = -0.83 cm % ,R = 0.98 Science 2012, 47, 1171. 012345 (19) Pullawan, T.; Wilkinson, A. N.; Eichhorn, S. J. Strain (%) Biomacromolecules 2012, 13, 2528. Figure 1 Shifts in the position of the Raman band located (20) Pullawan, T.; Wilkinson, A. N.; Eichhorn, S. J. at 1095 cm-1 as a function of tensile deformation for Compos. Sci. Technol. 2010, 70, 2325. samples both cured in, and without the presence of a magnetic field. Presented gradients are calculated from the fitted curves (3rd order polynomials) as a first derivative. ACKNOWLEDGMENT We thank the Royal Thai Government for a Ph.D. scholarship for T.P. REFERENCES (1) Eichhorn, S. J. Soft Matter 2011, 7, 303. (2) Eichhorn, S. J.; Dufresne, A.; Aranguren, M.; Marcovich, N. E.; Capadona, J. R.; Rowan, S. J.; Weder, C.; Thielemans, W.; Roman, M.; Renneckar, S.; Gindl, W.; Veigel, S.; Keckes, J.; Yano, H.; Abe, K.; Nogi, M.; Nakagaito, A. N.; Mangalam, A.; Simonsen, J.; Benight, A. S.; Bismarck, A.; Berglund, L. A.; Peijs, T. Journal of Materials Science 2010, 45, 1. (3) Klemm, D.; Kramer, F.; Moritz, S.; Lindström, T.; Ankerfors, M.; Gray, D.; Dorris, A. Angewandte Chemie International Edition 2011, 50, 5438. (4) Habibi, Y.; Lucia, L. A.; Rojas, O. J. Chemical Reviews 2010, 110, 3479. (5) Klemm, D.; Heublein, B.; Fink, H. P.; Bohn, A. Angew. Chem.-Int. Edit. 2005, 44, 3358. (6) Marchessault, R. H.; Morehead, F. F.; Walter, N. M. Nature 1959, 184, 632. (7) Revol, J. F.; Bradford, H.; Giasson, J.; Marchessault, R. H.; Gray, D. G. International Journal of Biological Macromolecules 1992, 14, 170. (8) Revol, J. F.; Godbout, L.; Dong, X. M.; Gray, D. G.; Chanzy, H.; Maret, G. Liq. Cryst. 1994, 16, 127. (9) Sugiyama, J.; Chanzy, H.; Maret, G. Macromolecules 1992, 25, 4232. Electrospinning Hyaluronic Acid Laura J. Toth and Caroline L. Schauer Drexel University [email protected]

STATEMENT OF PURPOSE/OBJECTIVE degradation of HA and may be what is taking place in the Natural polymer nanofibers are the focus of many studies highly basic NaOH-based solutions. Previous work by the due to their biocompatibility and inherent functionality. authors has eliminated this possible degradation via the However, the highly charged nature of natural use of a less basic ammonium hydroxide solution.8 Fibers polyelectrolytes such as chitosan, hyaluronic acid, pectin, were produced with an average diameter less than 100 and chondroitin sulfate make them a challenge to nm. electrospin. This paper focuses on electrospinning pure hyaluronic acid and crosslinking the resulting fibers to prevent dissolution for possible applications in tissue engineering.

INTRODUCTION Hyaluronic acid (HA) is a major glycosaminoglycan found in the extracellular matrix (ECM) of mammalian connective tissue. It is a linear natural polysaccharide composed of the repeating disaccharide β-1-4-D- glucuronic acid and β-1-3-N-acetyl-D-glucosamine. Because HA has demonstrated to be a biocompatible polymer, there has been extensive research into its potential for biomedical applications. Due to it being a primary ECM component, HA has been investigated as scaffolding material for cartilage tissue engineering in the treatment of arthritis.1-4 The anionic and hydrophilic nature of bulk HA does not favor the direct attachment of cells. Electrospinning is currently the most effective method for Fig. 1. SEM micrographs of 1.5 wt%/v HA in 1:1 H2O/DMF with 1:1 producing nanoscale nonwoven mats of natural polymeric Na2PO4:HA (top left) and a 2:1 Na2PO4 (top right); from 1:1(middle left) materials. However, there has been much difficulty in the and 4:1(middle right) HA:GP solutions; and from 1:1(left) and 4:1(right) HA:GP solutions. production of pure nanofibrous mats via electrospinning from a variety of natural polymers, including HA. HA forms a highly viscous solution at low concentrations, less than 5 w/v %, which severely hinders its electrospinnability. In addition, the anionic nature of the chains may contribute to electrostatic repulsion, preventing the chain entanglements required for successful electrospinning. As a result, there has been little published success in the production of pure HA nanofibrous mats. Um et al. has used an altered electrospinning setup, termed electroblowing, to create 5 Fig. 2. Fiber diameter distributions of HA/phosphorous salts. Glycerol such mats. Additionally, solvent systems consisting of phosphate (GP), sodium phosphate (SP) and tripolyphosphate (TPP) HA 6 dimethylformamide (DMF) and H2O as well as sodium solutions were spun from DMF:H2O. hydroxide and DMF3 have been reported in the literature. Despite many attempts, reproducing these results was APPROACH only possible using sodium hydroxide and DMF as the Our approach is to electrospin hyaluronic acid from solvent system. The fibers produced, however, had neutral solutions and investigate crosslinking pathways to average diameters well above 100 nm. Moreover, there create a more robust fiber mat for tissue engineering was a viscosity change observed within a short 30 min applications. time period after mixing of the HA in this solvent system. Materials: Cosmetic grade hyaluronic acid (HA) was obtained from Dali Chemical Company (Liuzhou, China) This severely hindered electrospinning, as the process 6 could not continue beyond this point. Maleki et al. have with a molecular weight of approximately 1.5 x 10 Da. shown HA to decrease in viscosity at the extreme ends of N,N-dimethylformamide (DMF). Glycerol phosphate the pH spectrum.7 They have attributed this change to the (GP), sodium phosphate (SP), tripolyphosphate (TPP), sodium hydroxide (NaOH), and divinyl sulfone (DVS) CONCLUSIONS were purchased from Sigma-Aldrich (St. Louis, MO) and Natural polyelectrolyte, hyaluronic acid was electrospun used as received. from neutral solutions and crosslinked using DVS to Preparation and electrospinning of HA polymer solution: create a chemically robust fiber mat. Solutions for electrospinning were prepared from HA (1.5 wt%/v) in a 1:1 DMF/dH2O solvent system. In order to FUTURE WORK crosslink the electrospun fibers, 60 wt % NaOH (0.3 Future work is to use these robust mats for tissue v%/v) as well DVS (0.3 v%/v) were added to the solvent engineering applications. system prior to electrospinning. HA solutions were loaded into a 10 mL Becton Dickinson (BD) syringe fitted with a 20 gauge needle and an 11 cm collection distance. The solution pump rate and voltage were set 0.9 mL/hr and 17 kV respectively. Fiber mats were spun for approximately five hours on a copper collecting plate coated with wax fiber for fiber morphology characterization.

Fig. 4. Immunofluorescent micrographs of HeLa cells grown on DVS- RESULTS AND DISCUSSION HA fiber mat (a). All cells display an extended morphology, indicating HA fibers were spun from neutral solutions utilizing cells were healthy. Magnified image of HeLa cells grown on HA fiber additional phosphorous salts of glycerol phosphate (GP), mat highlights F-actin (phalloidin green stain) differences among cells sodium phosphate (SP), and tripolyphosphate (TPP) (Figs. grown on HA fiber mats and glass coverslips. 1 and 2) In order to further validate crosslinked HA fibrous mats, a KEYWORDS transmission experiment utilizing a modified protocol Polyelectrolytes, hyaluronic acid, crosslinked fibrous used by our lab was employed (Fig. 3). Transmission at mats 600 nm was measured from fibrous mats exposed to acidic, neutral, and basic solutions. A transmission value ACKNOWLEDGMENT of greater than or equal to 90% indicates either (1) the The authors thank: Dr. Edward Basgall and the fibrous mat is fully crosslinked or (2) the fibrous mat is Centralized Research Facilities (CRF), College of dissolved. Engineering, Drexel University for use of FESEM and the sputter coater; Dr. Giuseppe Palmese for the use of the Fig. 3. Transmission measurements to determine if the mat dissolved ATR-FTIR; LJT acknowledges DOEd GAANN were run at different pHs. Fellowship 2012-2013 for support; The authors wish to acknowledge funding by the NSF CMMI Grant No. 0804543 and Ben Franklin Nanotechnology Institute, T Values for HA Crosslinked Mats 600nm Philadelphia, PA.

100 pH 2 REFERENCES 80 pH 7 1. Huskisson, E., Hyaluronic acid in the treatment of osteoarthritis of the pH 7 L-ala knee. In Br Soc Rheumatology: 1999; Vol. 38, pp 602-607. 60 pH 14 2. Ji, Y.; Ghosh, K.; Shu, X.; Li, B.; Sokolov, J.; Prestwich, G.; Clark,

600 nm 40 R.; Rafailovich, M., Electrospun three-dimensional hyaluronic acid T nanofibrous scaffolds. Biomaterials 2006, 27, (20), 3782-3792. 20 3. Kim, T.; Chung, H.; Park, T., Macroporous and nanofibrous hyaluronic acid/collagen hybrid scaffold fabricated by concurrent 0 electrospinning and deposition/leaching of salt particles. Acta s rs rs rs u u u Biomaterialia 2008. 5 min 5 min 5 min 15 min 1 1 1 72 hour 72 ho 72 ho 72 ho 4. Yoo, H.; Lee, E.; Yoon, J.; Park, T., Hyaluronic acid modified Fiber Mat Immersion Time biodegradable scaffolds for cartilage tissue engineering. Biomaterials 2005, 26, (14), 1925-1933. A value between 50-90% indicates partial crosslinking. 5. Um, I.; Fang, D.; Hsiao, B.; Okamoto, A.; Chu, B., Electro-Spinning As shown in Figure 2b, crosslinking HA fibrous mats and Electro-Blowing of Hyaluronic Acid. BIOMACROMOLECULES- with DVS greatly improves solubility. Crosslinked mats WASHINGTON- 2004, 5, (4), 1428-1436. 6. Li, J.; He, A.; Han, C.; Fang, D.; Hsiao, B.; Chu, B., Electrospinning exposed to a pH of both 2 and 14 resulted in greater than of Hyaluronic Acid (HA) and HA/Gelatin Blends. 90% transmittance after 15 minutes and were visible. MACROMOLECULAR RAPID COMMUNICATIONS 2006, 27, (2), 114. After 72 hours, the fibrous mat in a pH 14 solution was no 7. Maleki, A.; Kjoniksen, A.; Nystrom, B. In Effect of pH on the longer visible, and this dissolution was confirmed by the Behavior of Hyaluronic Acid in Dilute and Semidilute Aqueous Solutions, 2008; WILEY-VCH Verlag Weinheim: 2008. 90% transmittance value. 8. Brenner, E. K., Schiffman, J. D., Thompson, E. A. Toth, L. J., Schauer, C. L. Carbohydrate Polymers, 2012, 87, 926-929. “Electrospinning Hyaluronic Nanofibers from Aqueous Ammonium Solutions,” doi:10.1016/j.carbpol.2011.07.033.

Structure and Mechanical Properties of Silk-Inspired Flow-Assembled Fibers

Seunghwa Ryu1, Greta Gronau1, Michelle E. Kinahan2, Sreevidhya Tarakkad Krishnaji3,4, David L. Kaplan3, Joyce Y. Wong2, Markus J. Buehler1 1Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; USA 2Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA; 3Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA; 4Department of Chemistry, Tufts University, Medford, MA 02155, USA [email protected]; [email protected]

STATEMENT OF PURPOSE/OBJECTIVE We use a dissipative particle dynamics (DPD) model [3] We present a model for studying self-assembly of silk- to simulate hundreds of protein chains, described as a like polymers into fibers during a microfluidic spinning chain of particles with hydrophobic and hydrophilic process that mimics the spider's duct, integrating characteristics in explicit water. We coarse grain three computational and experimental work. We monitor the molecules into one DPD bead (hydrophobic or structural evolution and the associated mechanical hydrophilic) and 10 water molecules into one water bead. properties change under shear flow. While the mechanical Hydrogen bonding between hydrophobic peptides is taken strength of the fiber has been linked with the beta-sheet into account by attractive interactions, used to model the contents which provide the cross-link between peptides, strong cross-link provided by beta-sheet crystals. our study reveals that the overall connectivity of the polymer gel plays a more important role in determining We simulate the structural change of polymer solutions the resilience and strength of the fiber. Based on the during processing in the microfluidic device, as well as finding, we suggest the use of longer polypetide chains deformation during the mechanical test: (a) equilibration with multiple hydrophobic/hydrophilic blocks to in aqueous solution, (b) shear flow to model the flow synthesize robust fibers. Our study provides a strategy to condition in the microchannel, and (c) the uniaxial tensile better control mechanical properties of the synthetic loading test, as demonstrated in the Fig. 1. biomimetic fiber, as well as an insight on the natural spider silk spinning mechanism.

INTRODUCTION Spider silk fibers exhibit exceptional mechanical properties. The toughness is comparable to the Kevlar and the strength is comparable to steel yet six times light. Despite the weak and limited building blocks, spiders and silkworms produce fibers with such a remarkable combination of characteristics by engineering nanoscale morphology. To fully harness the advantage of silk fiber and control the properties, there have been extensive efforts to artificially synthesize the silk fiber with regenerative and recombinanat silk fibroins. Yet, its Figure 1. Overview of the silk spinning process reflected synthetic imitation has been hindered by the incomplete in our modeling approach. knowledge about the interplay between structure and processing. RESULTS AND DISCUSSION We first study the effect of the shear flow on the structure While we succeeded in spinning robust fibers from and strength of the fiber spun from regenerative silkworm regenerative silk in our recent microfluidic silk spinning fiber (RSF) which is modeled as multiblock copolymer, approach [1], we were not able to spin robust fibers from ABABABABAB where A and B represents hydrophobic spider silk inspired recombinant silk [2]. Even though the and hydrophilic segments of silkworm heavy chain materials made of recombinant silk have a similar level of peptide, as shown in the Fig. 2. After equilibration, an beta-sheet content with natural fiber, they are not able to isotropic polymer gel structure is formed with the cross- sustain any tensile loading. To better understand the links made of hydrophobic beads. Such polymer gel spinning process and resulting microstructure, we develop structure mimics the natural silk where the cross-links are a coarse-grained model that can span the relevant time provided by the beta-sheet crystal formed by hydrophobic and length scale of the spinning process. amino acids. Under shear flow, some portion of peptides are detached from the cross-links and extended along the APPROACH long axis of the fiber, which increases the average size of cross-links and the connectivity along the fiber axis. homogeneous distribution of cross-links, the connectivity of the material is very poor because short HAB3 peptide does not contribute to the connectivity. This provides an insight on the experiment where the fiber is very weak while the beta sheet content is comparable to natural fiber.

Figure 2. The microstructure of polymer gel from RSF solution after (a) equilibration and (b) shear flow. Hydrophobic and hydrophilic beads are represented by magenta and cyan color, respectively. For visualization purpose, water molecules are omitted in the figures. Figure 4. The microstructure of polymer gel from (a) To understand the effect of the microstructure on the HAB3/RSF blend and (b) HBA3/RSF blend. For the mechanical properties, we perform tensile loading tests recombinant HAB3/HBA3 peptides, hydrophobic and for two structures. Both elastic modulus and yield hydrophilic beads are represented by red and green color strength are increased after shear flow. The microscopic respectively. Hydrophilic beads in bridging peptides are structure change at the onset of the yield provides further selectively visualized, showing very poor connectivity of insights on the deformation mechanism, as well as the both materials. origin of strengthening due to shear flow. As visualized in Fig. 3, the tensile deformation proceeds in three steps: Based on the findings, we test the effect of peptide length extension of polymer chains, sequential unfolding of on the structure and mechanical properties of the fiber, polymer chain from the cross-links, and the escape of the using H(AB3)2, H(AB3)3, H(AB3)4 peptides, as polymer from the cross-links. More bridges between presented in the Table I. For the longer peptides with cross-links and larger cross-links size formed in shear more A-B blocks provide more bridges between the cross- flow make deformation process more difficult. Our links, enhancing both the connectivity and mechanical simulation demonstrates the importance of overall integrity of the fiber. Sequence Modulus Yield Average Number of connectivity for the resilience and strength of the fiber. Strength Bridges per Cross-Links H(AB3)2 0.1 0.05 2.1 H(AB3)3 0.25 0.2 3.9 H(AB3)4 0.6 0.5 4.7 Table I. Mechanical properties and connectivity for polymer gel structure made from three different length H(AB3)n peptides. All physical values are presented in dimensionless unit, using m=kBT=Rc=1 [3].

CONCLUSION In this work, we model the microfluidic spinning of using DPD and deformation mechanism. We find the increased connectivity during the spinning process, and identify that the importance of polymer gel connectivity in determining the resilience and strength of Figure 3. Deformation mechanism of polymer gel under the fiber. Based on the finding, we suggest the use of long tensile loading. Magnified view around the ruptured multiblock copolymer peptides to synthesize robust fiber. region. FUTURE WORK We then turn our attention to the effect of sequence by We are currently studying the length effect in microfluidic considering two spider silk-inspired peptides - HAB3 and spinning experiments. HBA3. Here, H is histidine fusion tag introduced to enable facile purification, A and B are hydrophobic and ACKNOWLEDGMENT hydrophilic segments of spider silk peptides. In We acknowledge the financial support from NIH/U01 experiments [2], we found that the HBA3 does not form EB014976 and ONR-PECASE N000141010562. fiber but globular structures due to its low solubility, whereas HAB3 does form fiber when mixed with RSF. REFERENCES However, fiber made from HAB3 blend is so weak that it [1] M. E. Kinahan et al, Biomacromolecules 12, 1504 breaks at any measurable tensile loading. We model the (2011). [2] S. Tarakkad Krishnaji et al, Advanced spinning of two blends, as shown in Fig. 4. HBA3 blend Functional Materials, in print. [3] R. D. Groot et al, form inhomogeneous clusters of hydrophobic beads with Journal of Chemical Physics 11, 4423 (1997). very few bridges. While HAB3 blend materials have

Submicron Fiber Nonwovens from Ingeo, a Sustainable Polymer

Gajanan Bhat1, Kokouvi Akato1, and Robert Green2 1The University of Tennessee, UTNRL, Knoxville, TN 37996, USA 2Nature Works LLC, Cary, NC, USA [email protected]

ABSTRACT

Ingeo is a biodegradable Polylactic Acid distance on the structure and properties of (PLA) polymer commercially produced and the nonwoven webs are being investigated. marketed by Natureworks. Polymers of this The resulting nonwoven webs are tested to class are making a significant impact in the determine fiber diameter, air permeability, plastics packaging industry by providing an porosity, filtration efficiency, and fiber alternative for producing compostable morphology. The study has shown that by materials. Filtration industry is one of the appropriately selecting the process largest growing sector that uses micron and conditions, fiber diameters of half micron or submicron fiber nonwoven webs. A melt less can be achieved, and these provide blown grade PLA was processed on a pilot exceptional performance in desired scale Melt blowing equipment at the applications. The development of structure University of Tennessee Nonwovens and properties during processing of this Research Laboratory. Effect of special die biopolymer into submicron fibers will be and processing conditions such as melt discussed. temperature, air volume and die to collector

Biology and Health

Green Engineering of Antimicrobial Nanofiber Mats

Katrina A. Rieger, Nathan P. Birch, Nathaniel Eagan, Jessica D. Schiffman Department of Chemical Engineering, University of Massachusetts Amherst [email protected]

INTRODUCTION statistically increases the antibacterial activity of the mats, Indwelling medical devices account for one-half of all up to 75 ± 7.9% for the mats containing a five volume nosocomial infections, and frequently, the device ― a percent loading of CA.11 catheter, intubation tube, implant, or shunt ― must be removed. One potential way to prevent biofilm formation CONCLUSIONS on indwelling medical devices is to coat them with The colonization of medical devices by bacterial biofilms antimicrobial compounds. However, the use of antibiotics is a problem of increasing concern. Biofilms are difficult leads to undesired consequences, including the spread of to eradicate, and the increased prevalence of antibiotic- antibiotic-resistant bacteria. For example, 60% of resistant organisms makes bacterial infection an even Staphylococcus aureus strains isolated from intensive care greater risk. Nanofiber mats that immobilize volatile units were resistant to methicillin.1 The increasing trend essential oils, offer an opportunity to supply bioactive in antibiotic resistance correlates to the increasing use of compounds at the source of the potential biofilm-related inorganic antimicrobials. Incorporating silver ions into the infection where and when they are needed the most. polymer precursor solution is the most common method of imparting biocidal properties to electrospun fiber mats. KEYWORDS This has been demonstrated using cellulose acetate, Antibacterial, Biofilm, Biopolymer, Electrospin polyacrylonitrile, poly(vinylchloride), poly(L-lactide), and poly(vinyl alcohol).2-6 Additionally, the surface of ACKNOWLEDGMENT polysulfone mats have been modified with highly active, This work was supported by the NSF Center for small diameter silver nanoparticles.7 While these Hierarchical Manufacturing at the University of nanofiber mats are effective at inactivating bacteria, the Massachusetts (NSEC, CMMI-1025020). use of silver is also problematic. Silver resistance has been observed in bacteria, notably Pseudomonas REFERENCES aeruginosa.8 Therefore, engineered materials, which can 1. Ramritu, P.; Halton, K.; Collignon, P.; Cook, D.; deliver antimicrobial compounds but not encourage the Fraenkel, D.; Battistutta, D.; Whitby, M.; Graves, N., spread of resistance genes are needed to improved the American Journal of Infection Control 2008, 36, 104-117. outcomes of patient health. 2. Park, S.-W.; Bae, H.-S.; Xing, Z.-C.; Kwon, O. H.; Huh, M.-W.; Kang, I.-K., Journal of Applied Polymer Recent work9, 10 confirms that essential oils derived from Science 2009, 112, 2320-2326. plants can serve as effective antimicrobial agents. When 3. Teo, W.-E.; Ramakrishna, S., Composites Science and incorporated into a biodegradable, poly(lactic-co-glycolic Technology 2009, 69, 1804-1817. acid) thin film coating, cinnamaldehyde (CA, from 4. Hong, K. H., Polymer Engineering & Science 2007, 47, cinnamon) was effective at preventing young biofilms by 43-49. Staphylococcus aureus and Pseudomonas aeruginosa. 5. Son, W. K.; Youk, J. H.; Lee, T. S.; Park, W. H., However, the controlled delivery of CA has not yet been Macromol. Rapid Commun. 2004, 25, 1632-1637. explored. In this work we electrospin chitosan-based 6. Lala, N. L.; Ramaseshan, R.; Bojun, L.; Sundarrajan, nanofiber mats engineered to release CA at a S.; Barhate, R. S.; Ying-jun, L.; Ramakrishna, S., physiologically relevant pH. These mats offer Biotechnology and Bioengineering 2007, 97, 1357-1365. applicability as broad-spectrum green alternative biocidal 7. Schiffman, J. D.; Wang, Y.; Giannelis, E. P.; coating. Elimelech, M., Langmuir 2011, 27, 13159-13164. 8. Silver, S.; Phung, L.; Silver, G., Journal of Industrial RESULTS AND DISCUSSION Microbiology & Biotechnology 2006, 33, 627-634. Chitosan-based nanofiber mats that immobilize CA have 9. Kavanaugh, N. L.; Ribbeck, K., Applied and been successfully electrospun. Nuclear magnetic Environmental Microbiology 2012, 78, 4057-4061. resonance (NMR) confirms the chitosan-CA reaction 10. Zodrow, K. R.; Schiffman, J. D.; Elimelech, M., responsible for immobilizing the volatile essential oil. We Langmuir 2012, Accepted, DOI: 10.1021/la303286v. have demonstrated that at physiologically relevant pHs, 11. Rieger, K. A.; Birch, N. P.; Schiffman, J. D., the reaction can be reversed and a controlled release of Functionalizing electrospun polymer nanofiber mats to CA from CA-loaded fibers is possible. After 180 min of accelerate wound healing. In Nanomedicine, Wiley: incubation the control mats, due to their chitosan content Submitted. alone, can inactivate 47 ± 4.4% Pseudomonas aeruginosa. The availability of the CA to interact with the bacteria Antimicrobial Finishing of Polyester and Cotton Fabrics

Idris Cerkez, S. D. Worley, R. M. Broughton Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 36849 [email protected]

K OBJECTIVE N O O The objective of this study is to develop stable, NH rechargeable, and effective antimicrobial coatings MeOH, AIBN CH C CH2 C 2 o for cotton, polyester, and cotton/polyester blend 60 oC, 5 h n DMF, 65 C-5h n O O O fabrics that could potentially be used in medical O O O textile industry. CH CH2 CH2 2

HO HO HO

CH CH INTRODUCTION 2 CH2 2 Cl Cl N O N-halamines are one of the most effective biocides O that inactive a broad spectrum of microorganisms NH including Gram-negative and Gram-positive bacteria, viruses, fungi. The mechanism of action Chlorination CH2 C CH2 C for the biocidal activity is believed to be direct (for n Inactivation n O O stable N-halamines) and/or indirect (for less stable O O

N-halamines) transfer of the oxidative halogen to CH2 CH2 the cell membrane of microorganisms causing HO HO oxidation of amino acids which results in cell CH2 CH2 N O N O inactivation within brief contact times [1,2]. N- O O halamine coatings on various polymers have been NH N studied extensively due to their rechargeabilities, Cl HP HP-Cl long-term stabilities, and nontoxicities [3]. However, recent studies revealed that most of these FIGURE 1: Synthesis of N-halamine homopolymer coatings undergo photolytic degradation in the presence of UVA photons. Therefore, in this study, RESULTS AND DISCUSSION a new N-halamine monomer was synthesized, Stabilities of the coatings characterized, and used to make antimicrobial The stabilities of the coatings against repeated coatings on cotton, polyester, and cotton/polyester laundering and UVA light exposure were blend surfaces in order to improve the UVA light evaluated. It was found that the coatings were stabilities of these coatings. stable up to 50 times of laundering such that only around 25 % of the coatings were washed away EXPERIMENTAL from the surfaces. Because the synthesized The N-halamine homopolymer was synthesized polymer is water insoluble, the hydrogen bonding using, 3-chloro-2-hydroxypropylmethacrylate as and the secondary ionic forces were sufficiently starting material. First, the monomer was strong to maintain the polymer anchored to the polymerized by free radical polymerization, and surfaces during washings. On the other hand no then the potassium salt of 5,5-dimethylhaydantoin significant difference was observed for the was attached to the polymer (Figure 1). The 1 13 polyester and polyester/cotton fabrics. polymer structure was characterized by H, C In general, the UVA light stabilities on both NMR, and ATR-IR spectra. surfaces were remarkably better than most of the The synthesized polymer was dissolved in coatings studied previously on cotton surfaces [4]. ethanol/water mixture at different concentration, Moreover, the coatings were more stable on and coated on the fabrics using a laboratory polyester surfaces compared to polyester/cotton. wringer. After drying at 165 °C for one hour, the This could be due to the presence of UV absorbing fabrics were rendered biocidal upon exposure to additives introduced to fibers during extrusion dilute household bleach for one hour at room which results in less damage to the coatings and/or temperature. The existence of the coatings on the higher tendency toward photodegradation of surfaces was confirmed by ATR-IR spectroscopy. cotton fabric leading to dissociation of the coating polyester/cotton surfaces against UVA light from the surfaces[5,6]. exposure were inferior to polyester fabrics. No significant difference was observed in the washing Biocidal Efficacies stabilities of the coatings on both types of surfaces. The fabrics were challenged with Staphylococcus aureus (ATCC 6538) and Escherichia coli REFERENCES O157:H7 (ATCC 43895) using a “sandwich test. [1] A.E.S.I. Ahmed, J.N. Wardell, A.E. The chlorinated fabrics exhibited superior Thumser, C.A. Avignone-Rossa, G. Cavalli, antimicrobial activity with a complete inactivation J.N. Hay, M.E. Bushell, Journal of Applied of the bacteria within 30 to 60 min of contact time Polymer Science, 119 (2011) 709-718. (Table 1). On the other hand, the unchlorinated [2] S.P. Denyer, G. Stewart, International samples provided limited reduction due mainly to Biodeterioration & Biodegradation, 41 the adhesions of the bacteria to the surface. It was (1998) 261-268. found that increasing chlorine loading reduces the [3] S.D. Worley, D.E. Williams, Critical contact time for complete inactivation. The Reviews in Environmental Science and coatings were more effective on PET/cotton Technology, 18 (1988) 133-175. surfaces than PET surfaces due to reduce [4] X. Ren, L. Kou, J. Liang, S.D. Worley, hydrophobicity resulting in better contact with Y.M. Tzou, T.S. Huang, Cellulose, 15 microorganisms. (2008) 593-598. [5] G.J.M. Fechine, M.S. Rabello, R.M. Souto- TABLE 1: Biocidal efficacies of the coatings Maior, Polymer Degradation and Stability, Contact 75 (2002) 153-159. Samples time Bacterial reduction (log) [6] K.R. Millington, L.J. Kirschenbaum, (min) Coloration Technology, 118 (2002) 6-14. E. coli S. aureus a O157:H7 b PET/Cot 60 0.11 0.07 PET 60 0.25 0.04 5 3.92 0.97 PET/Cot 10 4.62 4.31 Cl+%=0.35 30 6.45 6.44 60 6.45 6.44 5 0.79 0.13 PET 10 1.93 0.53 Cl+%=0.33 30 6.45 3.71 60 6.45 6.44 aThe inoculum concentrations were 6.45 logs bThe inoculum concentrations were 6.44 logs.

CONCLUSIONS A new N-halamine polymer was synthesized, characterized, and coated on polyester and polyester/cotton surfaces by a pad-dry procedure. The chlorinated fabrics exhibited about six logs reduction of S. aureus and E. coli O157:H7 within 30-60 min of contact time. The chlorine stabilities against UVA light exposure and repeated launderings were adequate for use in industrial applications. It was found that the coatings functioned with more rapid antimicrobial activity on polyester/cotton blend, as the cellulosic part increased the hydrophilicity of the surfaces resulting in better contact with the bacteria. On the other hand, the stabilities of the coatings on The Effect of Needlepunched Nonwoven Fabric on Controlling Hyperhydricity of Scutellaria Species In Vitro Liquid Culture Systems

M. Tascan1, J. Adelberg2, A. Tascan1, N. Joshee3, and A. K. Yadav3 1Industrial Engineering, Zirve University, Gaziantep, Turkey 2Department of Horticulture, Clemson University, Clemson, South Carolina, USA 3Agricultural Research Station, Fort Valley State University, Fort Valley, Georgia, USA [email protected]

INTRODUCTION The effect of needlepunched nonwoven fabric on controlling Scutellaria baicalensis, S. costaricana and S. lateriflora plantlets hyperhydricity of Scutellaria species (Scutellaria lateriflora, S. were provided from department of Horticulture of Fort Valley costaricana and S. baicalensis) in vitro liquid culture systems was State University (Fort Valley, GA). investigated. Plants need an interface between the liquid with nutrients (nutrients in water) and their roots. In nature, soil is the Matrix Effect Experiment interface between the water and the plant. In laboratory conditions, Plantlets were cultured on four different physical states: Agar- soil is not used as an interface because of its disadvantages. For gelled culture, liquid stationary culture (LS) and two liquid years, the jelled media surface (agar) is used as an interface in cultures with needlepunched nonwoven fabrics. Each vessel laboratories all over the world. Because of higher viscosity in agar contained six nodes placed in Magenta GA7 with 30mL of initial compared to water, roots can not take the water into plants very media for agar, LS and fiber 30, and liquid culture with polyester quickly. The viscosity of agar balances the time and the speed of fiber that has 20mL initial media volume (fiber 20), which had the nutrients taken by plant. Needlepunched nonwoven fabric was additional 5mL of media volume at week 4 and week 6. used as an interface in this research. The growth response of Treatments with fabrics that contained needlepunched nonwoven Scutellaria species between the agar, needlepunched nonwoven fabric and seed germination paper were placed into Magenta GA7 fabric and no interface (root interacts directly with liquid nutrients) boxes stacked in the order of fabric, paper and plant respectively. was examined. 1: Dead plantlets, or very swollen leaves and stems Hyperhydricity is a physiological disorder, which may occur in A B C tissue culture environment. Hyperhydricity can be a major problem for in vitro plant production. Ziv [1] showed that hyperhydricity occurs when tissue absorbs excess amount of water from the culture environment. Saher et al. [2] report that hyperhydric tissue has translucent appearance with curled, wrinkled, elongated, water-soaked, thick, brittle leaves and has 2: Very brittle or succulent, crunchy or curly leaves with very thin, or shorter internodes. For centuries, plant products have been used as swollen stem turning purple or dark green medicine and cosmetic products [3]. Scutellaria contains over 300 A B C species with many known medicinal plants. Scutellaria spp. was used in various cultures as medicinal plants [4, 5]. Scutellaria lateriflora is native to North America and has been used as anti- depressant besides its ethnic usage. Aerial and root portion is rich

with flavonoids. Scutellaria costaricana is native to Costa Rica 3: More leaves still brittle, strong stem and has been used as an ornamental plant. Scutellaria baicalensis A B C is native to China, India and Korea and has been used as anti- cancer agent beside its traditional usage. The effect of different supporting materials on %DW, multiplication ratio, and hyperhydricity, as affected by agar, liquid medium, and liquid medium with nonwoven polyester fabric was investigated in this research. All treatments had 30ml media per 4: Most leaves supple, not brittle, very healthy stem vessel and an additional treatment fiber 20 starting with 20ml A B C initial media (and two additional 5ml of media at weeks 4 and 6).

MATERIALS AND METHODS Needlepunched nonwoven fabric was produced in Material 5: Almost perfect plantlets, supple leaves or stems Science and Engineering of Clemson University. Nonwoven fabric A B C (Table I) was made from 15 denier polyester fiber with two inches in length. Premixing was achieved by the CMC Rando Cleaner. Then, fibers were fed through a chute, which feeds the fibers to the 50cm card, and the web was fed onto a 60 cm Automatex cross lapper conveyor system. Fabric was then needle punched by Automatex Needle Punching around 50st/m for handling purposes Figure 1. Subjective hyperhydricity scale for Scutellaria species with weight of 150g/m². Two layers of slightly needled fabric were needlepunched again at around 250st/m to produce Fiber 20 Nodes were placed on the seed germination paper. Harvesting was samples. Three layers of slightly needled fabric were conducted at 2nd, 4th, 6th and 8th week. The experiment was needlepunched again at around 250st/m to produce Fiber 30 conducted in a completely randomized design with four treatments samples. Fibers were cut into uniform sizes (5cmx5cm), rinsed and three replicates. Plantlets were blotted on paper toweling, and with distilled water and dried before put into the vessel. Thickness the measurements were taken as fresh weight (FW), dry weight is measured according to the ASTM D-1777-96 stardard. (DW), and hyperhydricity (by visual assessment). Plantlets were Table I. Nonwoven fabric properties used for experiments put in paper envelopes and dried at 80ºC for 48 hours. The dry Sample Name Thickness, cm Weight, g/m² weight was then measured. Hyperhydricity measured by visual Fiber 20 0.508 245 assessment with a 1-5 numerical scale that presents degree of hyperhydricity. Fiber 30 1.143 381 Multiplication ratio = (Harvested # of nodes) / (Initial # of nodes)

Percentage dry weight (%DW) = (Dry weight / Fresh Weight) X 100 Figure 4. Multiplication ratios of Scutellaria baicalensis plantlets on agar, fiber and immersed liquid after 8 weeks in vitro. The data were analyzed with SAS 9.1 (SAS Inst. Cary, NC) and mean separation was determined using Fisher’s LSD (α=0.05). RESULTS AND DISCUSSION Scutellaria species grew at different rates and had different multiplication ratio. However, plantlets of different species responded similarly for hyperhydricity and %DW. Plantlets in liquid culture for all species were hyperhydric and yielded the lowest multiplication ratio. Plantlets in fibers and agar were less hyperhydric the entire time. A subjective scale for hyperhydricity was established for Scutellaria species. Figure 1 presents plantlets that show the range of hyperhydricity responses that were scored Figure 5. Hyperhydricity of Scutellaria lateriflora plantlets on agar, fiber on a numerical scale, 1 to 5. Figure 2 is shown as an example of and immersed liquid after 8 weeks in vitro. showing the growth response of Scutellaria Baicalensis at week 8. Plantlets from agar had higher hyperhydricity, however, less %DW compared to fiber plantlets. Agar and liquid culture plantlets had absorbed more water compared to the fiber plantlets. Multiplication ratio was similar for plantlets kept in the gaseous phase, agar, fiber 20 and fiber 30, compared to plantlets immersed in the liquid. It is assumed plantlets that absorbed excess amount of water might suffer with hypoxia stress, which may cause stress metabolism and reduced growth. Media color was darkened to tan for S. costaricana plantlets immersed in the liquid. It is assumed Figure 2. Growth Response of Scutellaria Baicalensis at week 8 on Agar, that these plantlets might be produced stress related phenolic. As Liquid Culture, Fiber 20, and Fiber 30. with S. lateriflora, plantlets immersed in liquid became more Scutellaria baicalensis plantlets in agar, fiber 20 and fiber 30 had hyperhydric without any limitation to media uptake. Fiber matrix similar multiplication ratio at the end of 8 weeks (Figure 4). appears to reduce media uptake and hyperhydricity as it keeps Multiplication of liquid culture plantlets was severely reduced over plantlets in the gaseous phase. time for all Scutellaria species. Lowered multiplication ratio might be related to hyperhydricity. Plantlets in liquid culture became hyperhydric and did not multiply or grow. CONCLUSIONS Plantlets grown on fiber generally resulted in the least hyperhydricity and relatively high multiplication ratio for all species. The fiber structure may help to reduce water uptake and keep plantlets in the gaseous phase. The only difference between fiber 20 and fiber 30 was the surface area of contact between the explants and media during the first 4 weeks of culture. However, plantlets in fiber 20 often had higher % DW compared to fiber 30 plantlets. Beside the difference of contact surface, there was no difference for hyperhydricity. Keeping plantlets in the gaseous phase, using floating paper and agar, resulted in better quality plantlets (less hyperhydric) with a higher multiplication ratio compared to immersing plantlets into the liquid phase. Fiber Figure 3. Percentage dry weights of Scutellaria costaricana plantlets on creates a matrix system that reduced media uptake, prevents agar, fiber and immersed liquid after 8 weeks in vitro hyperhydricity and may help to improve biomass production. All Scutellaria (costaricana, lateriflora, and baicalensis) plantlets in fiber had significantly higher %DW for the entire 8 week compared to agar and liquid plantlets. Figure 3 shows the %DW of REFERENCES Scutellaria costaricana plantlets on agar, fiber and immersed 1. Murahsige T. and Skoog F., A revised medium for rapid growth liquid after 8 weeks as an example. and bio-assays with tobacco tissue cultures, Physiol. Plant., 15, Plantlets grown in the gaseous phase - fibers and agar - were not 473-497 (1962). hyperhydric after 8 weeks, and plant quality increased with time 2. Ziv M, Simple bioreactors for mass propagation of plants, pp compared to plantlets immersed in liquid (Figure 5). It may be 79-95), Hvoslef-Edie And Preil, Liquid Culture Systems for in noted that fiber 20 and fiber 30 plantlets had higher %DW, less vitro Plant Propagation, Springer, Netherlands (2005). hyperhydricity and relatively high multiplication ratio. 3. Franck T, Kevers C, Gaspar T, Dommes J, Deby C, Greimers R, Serteyn D and Deby-Dupont G, Hyperhydricity of Prunus avium shoots cultured on gelrite: a controlled stress response, Plant Physiology and Biochemistry, 42, 519-527 (2004). 4. Nalawade SM and Tsay H, In vitro propagation of some important Chinese medicinal plants and their sustainable usage, In vitro Cell Development Biology-Plant, 40, 143-154 (2004). 5. Joshee N, Patrick TS, Mentreddy RS and Yadav KA, Skullcap: Potential medicinal crop, herbs, Medicinals and aromatics trends in new crops and new uses, ASHS Press, Alexandria, VA, 22-30 (2002).

Amidoximated Bacterial Cellulose as an Effective Nanoreactor for In Situ Synthesis of ZnO Nanoparticles

Weili Hu, Shiyan Chen, Bihui Zhou, Huaping Wang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, 201620, P R China [email protected]; [email protected]

INTRODUCTION degradation of methyl orange (MO) solution based on the Bacterial cellulose (BC) as a novel biosynthesized cellulose has previous reported procedure15. gained more and more attention these years for the favorable properties it possesses. BC is generated as an ultrafine nanosized RESULTS AND DISCUSSION three-dimensional fibrous network comprised of the ribbon- The Am-BC membrane possesses an exquisite three dimentional shaped nanofibers with diameters of 10~100 nm1. It has high network structure which could provide a good tunnel for the purity, crystallinity, specific surface, mechanical properties and adsorption Zn2+ and lead to the homogeneous distribution of good biocompatibility2. Taking advantage of these unique Zn2+ on the nanofibers12. During the synthesis process, zinc ions characteristics, BC can be used as a “nanoreactor” to synthesize are incorporated and anchored onto the stable absorption site by nanomaterials with specific shape and size through its three the strong interactions between Zn2+ and hydroxyl and amino dimensional and porous network and certain nano-pore size groups of Am-BC. Then a sufficiently rinsing step was taken to distribution3. Some researchers have done many investigations remove unanchored Zn2+. The as-anchored Zn2+ can undergo regarding the application of BC as a nanoreactor to obtain hydrolysis and polymerization to form the ZnO nanoparticles in nanomaterials such as noble metal, CdS and CdSe nanoparicels the presence of water through a polyol meditated synthesis as and PANI nanosheath3-7. However, the properties of these shown in Fig.1. With the aid of Am-BC, the ZnO nanoparcticles obtained composites are unsatisfactory with a low yield and have the tendency to grow into relatively equiaxial particles and sparse distribution of nanoparticles due to the relatively weak to be anchored at the ex-absorpted sites, preventing the electrostatic interactions which shows the problem in anchoring nanoparticles from aggregating. plenty of metallic ions onto BC fibers8, 9. For BC to be suitable as an effective nanoreactor to control the formation of nanomaterials, the chemical functionalization must be employed to modify the BC fibers for imparting BC membranes with new functionalities and producing BC nanocomposites with tailored characteristics. Several approaches for the modification of BC substrates have been suggested during the last decades2, 8, 10, 11. Fig. 1. Schematic diagram of the formation of ZnO nanoparcticles onto nanofibers of Am-BC membrane Our group has successfully prepared amidoximated BC(Am-BC) which can greatly absorb and stably anchor plenty of metallic 12, 13 The FESEM images of the ZnO nanoparticles synthesized under ions onto nanofibers from aqueous solutions . different concentrations of zinc ions are shown in Fig.2. The Herein we reported the in situ synthesis of well-controlled ZnO result indicated that the size and distribution of the particles are nanoparticles using Am-BC hydrogels as an effective greatly affected by the concentration of zinc ions. The increasing nanoreactor. Am-BC as host matrix can stably anchor numerous concentration of zinc ions can offer greater opportunities for znic ions and then as nanoreactors to fabricate ZnO Am-BC to anchor more Zn2+, resulting in larger amount of ZnO nanoparticles by hydrolysis of zinc acetate in a polyol medium. nuclei and higher loading of ZnO particles onto Am-BC The obtained ZnO/Am-BC nanocomposites have been nanofibers. But at the same time, the unstable particles on fibers characterized by FESEM, XRD, FTIR, and TGA analysis and may have the tendency of aggregation to form irregular larger the photocatalytic properties have been also studied. particles at higher concentration of zinc ions16. Hence, when the concentration of zinc ions is 0.05wt%, the obtained ZnO EXPERIMENTS nanoparticles with a uniform distribution and an average Purified BC membrane obtained from Acetobacter xylinum diameter of 50nm are anchored discretely onto the Am-BC cultures was prepared in our laboratory. The Am-BC was nanofibers. prepared in our laboratory according to the method reported12-14. 1.8g water-wet synthesized Am-BC membranes were dipped in 0.05wt% 、 0.1wt% 、 1wt% zinc acetate aqueous solution at room temperature for 2h. After rinsed with distilled water for three times, the Am-BC membranes, 5mL zinc acetate aqueous solution, 50mL diethylene glycol were mixed in a round bottom Fig. 2. FESEM images of ZnO nanoparticles synthesized at different flask and stirred vigorously in an oil bath at 170℃ for 10 min. concentration of zinc acetate: (a) 0.05wt%, (b) 0.1wt%, (c) 0.5wt%. The final composite membranes were washed with distilled water and ethanol and freeze-dried. Fig. 3 shows the X-ray diffraction patterns of the The morphology of ZnO/Am-BC nanocomposite was nanocomposites synthesized at different Zn2+ concentration. The investigated by FESEM (S-4800 field emission scanning broad diffraction peaks at 14.60°, 16.82° and 22.78° are electron microscope). The crystallinity and the phase assigned to the Am-BC fibers3, 7. The other characteristic peaks composition of samples were characterized by XRD (D/Max- at 31.72°, 34.38°, 36.20°, 47.54° and 56.54° correspond to the 2550 PC, Rigaku, Japan). FTIR spectra were recorded on a (100), (101), (002) and (102) crystal planes of wurtzite structure Nicolet NEXUS-670. TG was carried out with a Netzsch TG ZnO (JCPDS, 36-1451), respectively. No peaks from any other 209 F1 Iris under nitrogen atmosphere with a heating rate of impurities such as Zn(OH)2 are observed which demonstrates 20°C/min. The photocatalytic properties of the ZnO/Am-BC the high purity and crystallinity of the as-obtained samples. nanocomposites films were evaluated by the photocatalytic obtained at different concentration of Zn2+ have been shown in Fig.6 through photocatalytic degradation of organic such as methyl orange. The nanocomposites synthesized at 0.05wt% Zn2+ displays a higher decolorization efficiency of 91% at 120min, followed by 0.1wt% and 1wt%. It has been demonstrated that there is no obvious difference in the composited content of ZnO nanoparticles under different concentration of Zn2+. The different photocatalytic efficiency may be attributed to the change of specific surface areas and crystallite size of ZnO nanoparticles. Lower concentration resulted in the decrease of particle size and increase in surface Fig. 3. XRD pattern of ZnO/Am-BC synthesized at different area, which can make a positive impact on the photocatalytic concentration of zinc acetate: (a) 1wt%； (b) 0.1wt%； (c) 0.05wt% properties15.

To reveal the reactive site during hydrolytic process and evaluate the interaction between ZnO nanoparticles and Am-BC matrix, the FTIR spectra of BC, Am-BC and ZnO/Am-BC nanocomposite samples were analyzed shown in Fig.4. It can be seen that after the formation of ZnO nanoparticles, the peaks at 928 cm-1 and 1657 cm-1 corresponding to the stretching vibration of C=N and N-OH bonds are weakened and move slightly downfield to lower wavenumbers of 917cm-1 and -1 1630cm , respectively. The stretching vibrations of hydroxyl groups of Am-BC at 3400 cm-1 are shifted to 3425 cm-1 in the Fig. 6. Photocatalytic properties of ZnO/Am-BC nanocomposites spectrum of the nanocomposite. This phenomenon indicated synthesized with different concentration of Zn2+. that there is a strong interaction between the hydroxyl and amino groups of Am-BC and ZnO nanoparticles4, 10, 15. CONCLUSION In conclusion, using Am-BC as a nanoreactor, we have successfully fabricated nanocrystalline ZnO particles with a specific morphology and size by a simple polyol method. The results suggest that Am-BC as an effective nanoreactor plays an important role in preventing the ZnO nanoparticles from aggregating. Under optimized conditions, well-dispersed and regular ZnO nanoparticles can be in situ assembled into Am-BC network and high photocatalytic properties can be obtained. This method could also be used as a facile and effective approach to prepare various oxide or metal nanoparticles. Fig. 4. The FTIR spectra of (a) BC, (b)Am-BC, (c) ZnO/Am-BC nanocomposite ACKNOWLEDGMENT This work was financially supported by Program of Introducing Talents The thermal properties of Am-BC and ZnO/Am-BC of Discipline to Universities (B07024), Shanghai Leading Academic nanocomposites synthesized under different concentration of Discipline Project (B603), Project of the Action on Scientists and Zn2+ are illustrated in Fig. 5. The TG curve of ZnO/Am-BC Engineers to Serve Enterprises (2009GJE20016), and the Innovation nanocomposite is almost similar to Am-BC membrane. But the Funds for Ph. D Students (Weili Hu) of Donghua University. introduction of ZnO nanoparticles undermined the thermal stability of Am-BC, which also indicated the interaction REFERENCES 1.Gelin, K.; Bodin, A.; Gatenholm, P.; Mihranyan, A.; Edwards, K.; Strømme, M. between Am-BC and ZnO nanoparticles. The residues at 700 °C Polymer 2007, 48, (26), 7623-7631. could be referred to the content of ZnO nanoparticles which are 2.Hu, W.; Chen, S.; Xu, Q.; Wang, H. Carbohyd Polym 2011, 83, (4), 1575-1581. about 20.8%, 21.6%, and 22.9% for Am-BC nanocomposites 3.Hu, W. L.; Chen, S. Y.; Li, X.; Shi, S. A. K.; Shen, W.; Zhang, X.; Wang, H. P. synthesized with the concentration of Zn2+ at 0.05wt%, 0.1wt% Mat Sci Eng C-Bio S 2009, 29, (4), 1216-1219. 4.Li, X.; Chen, S. Y.; Hu, W. L.; Shi, S. K.; Shen, W.; Zhang, X.; Wang, H. P. and 1wt%, respectively. The content of the ZnO nanoparticles is Carbohyd Polym 2009, 76, (4), 509-512. very high, which proved the Am-BC is a highly effective 5.Yang, Z. H.; Chen, S. Y.; Hu, W. L.; Yin, N.; Zhang, W.; Xiang, C.; Wang, H. P. nanoreactor for the synthesis of nanoparticles at a high yield. Carbohyd Polym 2012, 88, (1), 173-178. 6.Maneerung, T.; Tokura, S.; Rujiravanit, R. Carbohyd Polym 2008, 72, (1), 43-51. 7.Hu, W.; Chen, S.; Yang, Z.; Liu, L.; Wang, H. The Journal of Physical Chemistry B 2011, 115, (26), 8453-8457. 8.Ifuku, S.; Tsuji, M.; Morimoto, M.; Saimoto, H.; Yano, H. Biomacromolecules 2009, 10, (9), 2714-2717. 9.Chen, P.; Cho, S. Y.; Jin, H. J. Macromol Res 2010, 18, (4), 309-320. 10.Hu, W.; Liu, S.; Chen, S.; Wang, H. Cellulose 2011, 18, (3), 655-661. 11.Oshima, T.; Kondo, K.; Ohto, K.; Inoue, K.; Baba, Y. React Funct Polym 2008, 68, (1), 376-383. 12.Chen, S. Y.; Shen, W.; Yu, F.; Hu, W. L.; Wang, H. P. J Appl Polym Sci 2010, 117, (1), 8-15. 13.Chen, S. Y.; Shen, W.; Yu, F.; Wang, H. P. Polym Bull 2009, 63, (2), 283-297. 14.Saliba, R.; Gauthier, H.; Gauthier, R.; Petit-Ramel, M. Cellulose 2002, 9, (2), Fig. 5. TG curves of ZnO/Am-BC nanocomposites synthesized with the 183-191. concentration of Zn2+ at (a) 1wt%, (b) 0.1wt% and (c) 0.05wt% and (d) 15.Hu, W. L.; Chen, S. Y.; Zhou, B. H.; Wang, H. P. Mater Sci Eng B-Adv 2010, Am-BC 170, (1-3), 88-92. 16.Tzeng, S. K.; Hon, M. H.; Leu, I. C. J Cryst Growth 2009, 311, (20), 4510-4517. The photocatalytic properties of ZnO/Am-BC nanocomposites Textile Heart Valve Prosthesis: Early In Vitro Fatigue Performances

Frederic Heim1, Bernard Durand1, Nabil Chakfe2 1Laboratoire de Physique et Mécanique Textiles EAC CNRS 7189, ENSISA, 11 rue Alfred Werner, 68093, Mulhouse, France 2Service de Chirurgie Vasculaire, Hôpitaux Universitaires de Strasbourg, 67000, Strasbourg, France [email protected]

INTRODUCTION Valve testing and evaluation Transcatheter (non invasive) aortic valve implantation has 6 textile valve prototypes were tested simultaneously on a become an alternative technique to surgical valve Dynatek Dalta M6 apparatus system at a 14 Hz cycling replacement in patients with high risk for open chest frequency (Fig.2). surgery [1,2]. Today, the valves used in non invasive valve surgery are made up with biological tissue. The tissue associated with metallic stents is however fragile material and becomes degraded during the crimping process. Heim et al showed that textile polyester is less fragile material and could be an alternative solution to replace valve leaflets [3]. The authors report about the good hydrodynamic performances obtained in vitro with the textile valve. Results are in the range of what is obtained with other commercially available valves. However, no information is available yet about the long Figure 2. Valve testing term fatigue behavior of the textile material. The purpose of the present work is to give early results obtained in After 10Mio cycles the valves were at first analyzed at vitro with a textile valve solicited under 14 Hz cyclic macroscopic level to evaluate material degradations loading. associated with cycling. Second, hydrodynamic performances (regurgitation) were measured on the valve APPROACH in a pulse duplicator at 70 bpm before and after cycling in Valve manufacturing order to assess the effect of cycling on the valve The valve was obtained from a tubular textile polyester performances evolution. Moreover, DSC analyses will (PET) membrane (plain weave, 60 yarns/cm, yarn count help assessing the physical transformation undergone by 60dtex) using a specific shaping process based on air the textile polymer. suction technology. During the process, the material was heated above polyester vitreous transition temperature in RESULTS AND DISCUSSION order to fix the obtained shape. Influence of the rigidity of the ring The tests had to be stopped at 1,2 Mio cycles with the metallic ring as some heavy ruptures occurred along the Valve preparation leaflet free edge (Fig. 3). The macroscopic evaluation of The shaped textile membrane was assembled with a these ruptures underline that the textile leaflet alone is not holding ring for an adapted positioning in the fatigue able to undergo the water hammer stress induced by the testing apparatus. In order to study the effect of the high cycling frequency. The valve holding device plays holding ring rigidity, two different materials were used an important role in damping the stress and needs to be for the ring: stainless steel and polymer (acetal resin). The flexible. With the prototypes mounted on the polymer assembling was realized using a suture yarn (Ethibon 4/0) ring, this phenomenon didn’t happen even at 20 Mio following the scalloped shape and an additional one at the cycles. basis of the cusp to secure the fixation (Fig. 1).

Figure 1. Valve ring assembling Figure 3. Valve degradation (rigid ring)

Influence of the assembling process construction. Basically, the rigidity due to friction is For the valves mounted on a polymer ring, some holes lower after than before cycling as the fabric undergoes a appeared at the basis of each cups on 3 of the tested yarn rearrangement process during the cycling process. prototypes at 10Mio cycles (Fig. 4). It seems the textile The leaflet being less rigid closes more rapidly, which was detached from the plastic structure due to local reduces the regurgitation values. rupture in the fabric at suture level. Insufficient suture points is the main cause of that phenomenon. Basically, Physical transformation in the polymer the bottom of the cusp is highly solicited under cyclic After macroscopic analysis of the valve prototypes at loading, which generates strong interaction between the 10Mio cycles, these were first put back in the testing fabric and the suture yarn. However, no other degradation device for further cycling. The goal is to assess how the was observed on the leaflet surface. initial ruptures observed in the fabric evolve over time, which is a critical issue in the valve application. After further degradation, the material will then be characterized for mechanical and physical transformation (DSC). The tests are still running now and the results will be available in the coming few days.

Figure 4. Valve degradation (polymer ring) CONCLUSIONS The early fatigue results obtained in this study show that Hydrodynamic performances the fabric degradation at 10Mio cycles occurs in zones Figure 5 represents typically the dynamic regurgitation where the textile is sutured to the holding ring. Suture obtained for the valve prototype before and after cycling. fixation should be improved in future experiments. However, sign of rupture could be observed neither on the leaflet surface nor in the contact zones where the leaflets come together. The global behavior of the fabric is encouraging.

REFERENCES [1] Davidson, MJ et al. “Percutaneous therapies for valvular heart disease,” Cardiovascular pathology, 15, 2006. 123-129. [2] Cribier, A et al. “Percutaneous Transcatheter Implantation of an Aortic Valve Prosthesis for Calcific

Aortic Stenosis, First Human Case Description,” Figure 5. Dynamic regurgitation Circulation, 106, 2002. 3006-3008. [3] Heim, F, Durand, B, Chakfe, N, “Textile Heart Valve One can observe that the cycling process induces a Prosthesis: Manufacturing Process and First in Vitro decrease in the dynamic regurgitation. This is associated Performances,” Textile Res J, 78, 2008. 1124-1131. with a decrease in the bending rigidity of the fabric

Investigation into New 3D Fibrous Structure for Soles Application

Mouna Messaoud1, Antoine Vaesken1, Laurence Schacher1, Dominique C. Adolphe1, Jean-Baptiste Schaffhauser2, Patrick Strehle2 1ENSISA, Laboratoire de Physique et Mécanique Textile, Université de Haute Alsace, France 2N. Schlumberger, France [email protected]

INTRODUCTION Up Laminating -layer In soles applications (products), comfort and cushioning Thermo-adhesive Pleated 3D web behavior (resilience) are the main properties required by customers. To insure these properties, the use of an Bottom Laminating -layer adequate material is needed. In fact, during walking action cushioning (resilient) materials are generally used Figure 1. The VERTILAP® 3D nonwoven to absorb kinetic mechanical energy under compression actions at a relatively constant stress. The comfort issue is The up laminating-layer was realized by the use of fibrous based on breathability of the sole structure and on webs or textile fabrics as illustrated in table 1. The bottom comfortable contact between the sole and the feet. layer was laminated with a light fibrous web (NW1). In addition, the question of the recycling in many industries represents one of the main requests and TABLE 1. The materials used for the laminating layer challenges in order to promote ecological methods of Up‐laminating layer NW1 NW2 L H1 H2 Type Fibrous web Fibrous web woven woven woven development in regard to new consumer sensibility. polyester In this work and based on all these facts, a new 3D Composition viscose Recycled PET Hemp Hemp fibrous structures (sheets) made of recycled polyester weight (g/m2) 45 110 240 190 440 (PET) material have been developed in order to develop Thickness (mm) 0.626 0.969 0.782 0.699 1.197 new soles for shoes wearers. It is produced thanks to a new patented process called VERTILAP from the N. Physical characterization SCHLUMBERGER Company [1]. In a previous study, The raw materials and the 3D fibrous structures for soles we have shown that the 3D fibrous structures are more manufacturing have been physically characterized by their resilient and dissipate more energy than polyurethane thickness (T), their mass per unit area (M), their air foams typically used for automobile industry. permeability (AP) and their absorption capacity (A). The In order to characterize some physical and mechanical pleated structure has been characterized by the number of properties of these new 3D fibrous structures, a pleats per cm (condensation rate), a parameter we can fix methodology has been set up and new testing methods during the manufacturing process. The thickness is have been developed. The results of this study have show measured thanks to the KES-FB3 compression tester of interesting properties of the new 3D nonwoven in terms the Kawabata Evaluation System for Fabrics. The of compression behavior and comfort for soles measuring conditions were as follow: the sample is application. compressed under a load of 0.05 kPa and a speed of 12 mm/min. The absorption capacity of the laminating APPROACH component and the final product has been measured by a For soles development, a pleated 3D fibrous structures prototype machine developed in our laboratory [2]. The have been manufactured from a 110 g/m2 recycled comfort of the raw materials used for the lamination of polyester webs (NPET). The pleats have been the pleated structure was evaluated by the measurement of manufactured under the glass transition temperature of the its thermal conductivity (k) and cool/warm touch (qmax). copolyester web which is 73 °C. Those single 3D pleated The comfort of soles was evaluated thanks to a panel of structures have been laminated from both sides thanks to users. The panel has tested different soles and evaluated a flatbed laminating unit. The thermo- adhesive used is a them based on certain criteria. 25 g/m2 copolyester nonwoven web. The single 3D Mechanical characterization fibrous structure, the adhesive and the laminating layers All the compression tests have been carried out on a are assembled and heated. After heating, the materials are universal screw driven testing machine (Instron 33R4204) pressed together with pressure rollers. Then, they are fitted with 5 kN load cell at at 0.05 mm/s solicitation guided through a cooled area. This process leads to a speed. In order to characterize the mechanical properties thermal and mechanical stability of the multilayered of these new 3D fibrous structure dedicated to soles structure (Figure 1). development, the maximum load and the absorbed energy at 20% and 50% of deformation have been evaluated and compared to data in literature [3].

RESULTS AND DISCUSSION 200 The results proved that the physical properties are linked at 20% of… to the VERTILAP process parameters in terms of at 50% of… condensation rate and the mass per unit area. Regarding 150 the standard deviation, the physical and geometrical parameters of the 3D fibrous samples are reproducible. 100 Indeed, the 3D structures are manufactured from an optimized semi-industrial prototype. In this work, the soles present a mass per unit area 50 between 962 and 1242 g/m2 and a thickness between 7.29 Maximum load (KPa) mm and 7.88 mm. The high value of the mass per unit 0 area and the thickness of the laminated 3D fibrous- NW1 NW2 L H1 H2 structure can be considered as negative in terms of dimensions for soles applications. So, these parameters Figure 3: Maximum load at 20% and 50% of deformation should be improved through the manufacturing process. Regarding the laminated products, the soles laminated up CONCLUSIONS and down with NW1 have the highest air permeability In this study, new 3D fibrous structures for soles due to their light structure but, the air permeability of the development were produced with a verticalization process final product (laminated soles) is mostly influenced by the newly patented. It is important to notice that the regularity density (the number of pleats per cm) of the pleated part which is a key point is fully controlled on this semi- of the sole. The hemp fabric has the highest qmax which industrial prototype. The manufactured 3D pleated means that a cool touch is insured between the foot and structures have been laminated with different textile the up-layer of the sole product. fabrics and have been tested. This new product has been Mechanical properties tested using a new customized procedure and comparison Figure 2 is displaying the compression behavior of the 3D has been done with literature dealing with foot anatomy fibrous structure NW1, given as an example. For the and walking action modeling. This investigation study has different products, a significant difference can be demonstrated the ability of the 3D fibrous structure to be observed between the 1st and the others cycles (2nd, 3rd, 4th reorganized under compression stress. It also highlights and 5th). A permanent or delayed thickness deformation is the relationship between the compressive mechanical observed after the 1st cycle therefore this deformation behavior and the resilience properties of these new soles decreases with repeated cycling. The new soles have a materials and their physical characteristics. good resilience and they dissipate more or less energy than the foams. FUTURE WORK This parameter is related to the ability of the 3D material The durability of the soles developed based on to absorb the energy applied on it, but also its recovery VERTILAP process should be evaluated under dynamic potentiality. As previously noticed, the 1st cycle presents compression loading. To do so, tests of dynamic higher value whatever the tested product is. The figure 3 compression (cyclic testing under low and medium shows that the maximum load value at 50% of frequency) will be realized. deformation is obtained in the case of the sample H2. This value is between the pressure of the midfoot (162 kPa) REFERENCES and the metatarsal region of the foot (443kPa) [3]. [1] J-L., Dumas, J-B., Schaffhauser, N. SCHLUMBERGER company, patent N° WO2007125248 (2007). [2] MARSIQUET Cyril, Laboratoire de Physique et Mécanique Textile. Réalisation d’un dispositif de mesure d’absorption capillaire, baptisé L.A.M. V2.0. 2010, 11 p. [3] FAIVRE Arnaud. Conception et validation d’un nouvel outil NW1 150 d’analyse de la marche. Thèse en Sciences et Techniques des Activités Physiques et Sportives. Besançon : université de 100 Franche-Comté, 2003, page 35. First cycle (kPa) 50 KEYWORDS Soles, 3D fibrous structure, compression behavior,

Load 0 resilience 01234 ‐50 ACKNOWLEDGMENT Displacement (mm) This work was performed in the frame of the VERTILAP Research project supported by “Pôle Véhicule de Futur” and “Pôle Fibres” competitiveness French clusters. The authors gratefully thank the Alsace Region and OSEO for financial support. Figure 2: Load-deformation curve of the sample NW1

Property Evaluation of Diabetic Socks Used to Prevent Diabetic Foot Syndrome

M. J. Abreu1, A. Catarino1, O. Rebelo2 1Textile Engineering Department, University of Minho, Guimarães, Portugal 2Center for Textile Science and Technology, University of Minho, Guimarães, Portugal [email protected]

STATEMENT OF PURPOSE Diabetes is a chronic disease which is increasing during the past years. Studies state that in 2025 the number of patients around the world will approximately be the double. Due to the complications promoted by diabetes, the patient looses sensitivity, but at the same time injuries are more complicated to be healed. Special care must take place with diabetic feet, namely by using proper shoes and socks, in order to avoid exceeding friction, sudation, high temperature, among other relevant factors. FIGURE 1. Example for the diabetic foot syndrome[3] One of the most serious problems for diabetic patients is called diabetic foot syndrome, that when neglected, can Special care must take place with diabetic feet, by using become dramatic, because in extreme cases, amputation proper shoes and socks. The available solutions for socks of the foot may occur. In this research we studied several include new raw materials with antimicrobial activity, socks, made with new and advanced materials and regenerating activity, temperature management, among diversified knitted structures, focusing on socks other characteristics. These socks can combine different commercially available and specially designed for knitted structures, especially in the heel, toes, instep and diabetic patients, in order to understand what would be bottom of the foot, contributing for an improved comfort the most adequate combination of structure and fibres that and promoting a better heat exchange [1,2]. would give the adequate results in terms of l properties The textile sector can and should contribute to a better using different equipment and to foreseen the possibility quality of life of diabetic patients, particularly with of indicating the most appropriate material/sock for the diabetic foot syndrome, applying their knowledge in different existing diabetic foot syndromes. terms of raw materials and combination of different knitted structures. INTRODUCTION Diabetes is a problem that affects millions of people EXPERIMENTAL APPROACH worldwide. In Portugal, Diabetes affects near 10% of the Tested Material Portuguese population and about 15% more are in danger At the beginning seven different commercially available of developing this disease. Consequences of diabetes are socks for diabetic patients were studied, composed by problems associated with the feet of these patients. functional fibres with antimicrobial activity, moisture Known as diabetic foot syndrome, the typical symptoms management and increasing the wound healing process can be lack or excess of sensitivity, poor blood combined with several types of knitting structures. circulation, bad tolerance to compression and difficulty to The Table 1 shows the composition for each one of the control hemorrhagic wounds [1,2]. seven socks, the knitting structure and the mass per unit There exist two types of diabetic foot syndrome: area. neuropathic and angiopathic syndrome. The first exists It should be noted that sock #2 is considered the reference when the diabetic patient is non sensitive against high sock for this study, since health professionals usually pressure points, lesions and temperatures. In the case of recommend socks based on cotton. angiopathic foot syndrome, lack of oxygen and nutrients The objectives of this particular study were to understand to the foot tissue exist [3], which can promote fat and the effect or influence of raw material and structure in blood clots to build up in the large blood vessels, stick to properties like thickness, water vapour permeability, air vessel walls, and block the flow of blood (Figure 1). permeability, thermal resistance and thermal conductivity. Patients with diabetes mellitus and peripheral neuropathy Moreover, understand underlying relationships between are at high risk for skin breakdown and subsequent lower- these properties for this particular kind of sock. As stated extremity amputation due to unnoticed repeated trauma to before, diabetic socks should take into account that the foot’s skin surface during walk [4]. diabetic foot requires improved protection for good temperature and moisture management.

TABLE I. Fibre Composition and Basic Characteristics for the The post-hoc tests were used to quantify which were the studied Diabetic Socks. socks that could be considered as having the same value Sock Composition Knitting Mass/Area 2 on a particular property. For example, for thickness, post- Code Structure (g/m ) hoc tests showed that there are three groups that can be 1 67%PA/15%PU/19%X-STATIC® Jersey 188 considered statistically different for a significance of 0,05. 2 97%CO/3%PU Jersey 218 Under this analysis, sock #2 and #5 would have similar 3 80%CO/12%PP/6%PA/2%PU Plush 475 thickness, while sock #1 presents an average value which 4 75%CO/19%CRABYON®/4%PA/ Jersey 227 2%PU is different from the other socks. Socks #4 and #6 can also 5 82%CO/9%X-STATIC®/6%PA/ Jersey 213 be considered as presenting similar results, being also the 3%PU highest ones. Similar analysis can be performed for the 6 97%COOLMAX®/3%PU Jersey 432 remaining properties. 7 86% ACRILICS/10%PA/3%PU Plush 647 CONCLUSIONS As it can be seen in Table 1, most of the socks present a The main findings of this study was that the 100% cotton jersey structure. Only socks #3 and #7 have a plush jersey sock, referred throughout this study as the standard structure. So, it was decided to eliminate these socks in sock, didn´t performed as expected for the studied the statistical treatment. properties. This sock has the highest thermal resistance and lowest conductivity, although it´s the thinnest one. Tested Properties This discovery is rather important, because this sock is Table 2 show the applied test methods and units in the referred as the most recommended sock for a diabetic study to ascertain the properties of the knitting structures patient with diabetic foot syndrome. However, its lower used for the diabetic socks. price makes this sock a strong competitor to all the other studied socks, including the ones with advanced or high TABLE II. Studied Properties, Test Methods and Units. performance fibres. These results reinforce the idea that Property Test Method Units actually there are other alternatives in terms of new fibres Thickness Manufacturer (KES- [mm] with high performance for this type of product. FB3) Considering the same structure, a thick sock may not be a BS 7209 [g/m2/day] Water Vapour synonym of a hot sock, with high thermal resistance, as Permeability Air Permeability NP EN ISO 9273 [l/m2/s] well as a light sock might not necessary mean that is very Thermal Properties: thin or present very high air permeability, since functional Thermal Conductivity Manufacturer [W/mºK] fibres and yarn properties may influence this behaviour. Thermal Resistance (Alambeta) [m2ºK/W] Beyond the observations and conclusions obtained during this research, an interesting suggestion resulted, that is the RESULTS AND DISCUSSION need for a classification of diabetic socks in two types: An objective analysis of the five selected socks was Socks recommended for the spring-summer; and socks conducted in order to determine which materials and recommended for the autumn-winter. This kind of structures were the most important for a patient with classification should be included on the diabetic sock diabetic foot, using SPSS for data analysis and statistical labels in order to elucidate “consumers” - diabetic patients tests. and prevent improper use of these socks. The table 3 summarizes the ANOVA and post-hoc tests conducted for the properties under study. ANOVA tests KEYWORDS showed that there exists a statistically significant Diabetic foot Syndrome, Advanced Materials, Properties. difference between the socks. REFERENCES TABLE III. Similarities between socks for each property, sorted [1] Abreu, M. J. ; Catarino, A.; Rebelo, O.; Duarte, F., Comparison from lower to higher values. between Human Physiological Response of Different Diabetic Socks, 41st International Symposium on Novelties in Textiles, Sock code and group by Ljubljana, Slovenia, 2010. similarities [2] O. Rebelo, A. Catarino, M. Abreu, M. Lima, Friction and Thickness 2,5 1 4,6 - - Compression Evaluation of Socks for Diabetic Patients, 5th Water 1,2,4,5 6 - - - International Textile, Clothing & Design Conference, Dubrovnik, Vapour Croatia, 2010. Permeability [3] Sailer, D.; Schweiger, H.: Der diabetische Fuss-ein Bildatlas, Deutscher Universitätsverlag, ISBN 3824421224, January 2000. Air 6 1 2 4 5 [4] Mueller, M. et al., Use of Computed Tomography and Plantar Permeability Pressure Measurement for Management of Neuropathic Ulcers in Thermal 1,5 6 4 2 - Patients with Diabetes, Physical Therapy, Vol. 79 Nr.3, (1999) Resistance 296-307. Thermal 1,2,4 5 6 - - Conductivity

Surface Properties

Butterfly-Inspired Fiber-Based Nanofluidics

Konstantin G. Kornev Department of Material Science and Engineering, Clemson University [email protected]

STATEMENT OF OBJECTIVE be applied to the production of micro and nanofluidic This talk reviews recent results on analysis of wetting devices with tunable wettability. and transport properties of feeding devices of moths The effect of fiber shape is analyzed theoretically and experimentally. We developed a new theory of and butterflies and development of artificial capillary rise by elliptical fibers and compared this proboscises for probing and analyses of minute amount theory with experiments. of liquids. Using X-ray phase contrast imaging we were able to INTRODUCTION observe the process of fluid imbibitions into the food The feeding device of almost 160,000 species of canal of a butterfly. It was discovered that the butterflies and moths is called proboscis and it is made mechanism of fluid intake drastically differs from the of a flexible fibers. The food canal of the proboscis is conventional textbook model of a drinking straw. The wettability and fluid intake analyses reveals active formed from two semi-cylindrical halves, the maxillary utilization of nano and microscales by the moths and galeae, that are linked together at their borders by butterflies. cuticular linkage devices. The proboscis can be considered as a flexible microfluidic device with We developed a technique to fabricate artificial extraordinary ability to probe, deliver, and sense proboscises from different polymers. Nanofibers have different fluids. Butterflies and moths not only imbibe been electrospun into ordered bands and subsequently floral nectar but also feed from rotten fruits and wet twisted into yarns by a specially designed instrument[2]. The artificial proboscises can be soil. The proboscis evolution, organization and produced on demand with a broad range of functionality are poorly understood, though its design permeability, from 10-14 m2 to 10-12m2. is attractive for making artificial probes. In this talk we will discuss recent results on the proboscis wettability Depending on the application, the probe can be made and fluid intake. Using these results, we will show a hydrophobic or hydrophilic and can be further range of possible designs of nanofiber-based probes. functionalized to perform different analytical tasks. An application of the fiber based probe to the PCR assay

of mRNA corresponding to a single cell level will be

demonstrated. RESULTS AND DISCUSSION

We used the butterfly proboscis to elucidate the ACKNOWLEDGMENT structural and chemical adaptations necessary for fluid acquisition with a primarily hydrophobic natural device. This work has been supported by National Science Using a capillary-rise technique and high speed flow Foundation, Grant No. EFRI 0937985. visualization, we studied the proboscis wettability and mechanisms of fluid uptake. We experimentally REFERENCES discovered and theoretically explained the essential [1] D. Monaenkova, et al., “Butterfly proboscis: role of morphological structure in partitioning of combining a drinking straw with a nanosponse feeding devices into wetting/nonwetting regions. It facilitate diversificationof feeding habits,” Journal of appears that the complex hierarchical morphology of the Royal Society Interface, vol. 9, pp.720-726, Apr the proboscis can be put within a physical theory of the 2012. wetting of rough surfaces. This classification allows one to explain the fluid partitioning on liquid bridges in [2] C. C. Tsai, et al., “Nanoporous artificial proboscis the food canal observed with X-Ray phase contrast for probingminute amount of liquids,” Nanoscale, vol. imaging [1]. The principles of compartmentalized 3, pp. 4685-4695, 2011. wettability of the butterfly proboscis has a far-reaching impact on the evolution of insect mouthparts and can Theoretical and Experimental Investigation of Non-Rotationally

Symmetrical Droplets on Fibers

Maofei Mei1, Jintu Fan1,2, Dahua Shou1 1Institute of Textiles and Clothing, The Hong Kong Polytechnic University 2Department of Fiber Science and Apparel Design, Cornell University [email protected]

ABSTRACT

Understanding the geometrical changes of principles governing the shape changes droplets on fibers during condensation or analyzed theoretically. Empirical evaporation is fundamental to many expressions were obtained to predict the applications of fibrous materials including geometry and mass of non-rotationally fiber filters, water harvesting, and functional symmetrical droplets on fibers of different clothing. However, the effect of gravity on radius. This study explains why condensed the geometry of droplets is still an unsolved water droplets on a fine fiber (like spider problem. In this work, the shape change of silk) maintains a seemingly beautiful droplets hanging from a horizontally rotationally symmetrical shape even though cylindrical fiber was investigated the size of the water droplet is far larger than experimentally and the underlining the radius of the fiber.

Optimization of Breathable Waterproof Coating Conditions for Minimizing Fabric Frictional Sound of Korean Military Combat Uniform Fabrics

Kyulin Lee and Gilsoo Cho Department of Clothing and Textiles, College of Human Ecology, Yonsei University [email protected]; [email protected]

INTRODUCTION #4 1 75 1 150 The breathable waterproof fabrics have two functions #5 -2 60 0 145 #6 2 80 0 145 which are permeability of vapor and repellency of water. #7 0 70 -2 135 However, it has been found that finished (coated or #8 0 70 2 155 laminated) fabrics for these functions generate the #9 0 70 0 145 frictional noise over 70dB [1]. When the breathable waterproof coating is applied to Specimens and treatment combat uniform fabrics, it could be a much more serious Ten pieces of combat uniform fabrics (uncoated) with problem. Because the combat uniform’s loud fabric digital patterns were prepared. Nine of the fabrics were frictional sound could expose the wearer to the enemy coated with mixture of polyurethane based agent and poly when soldiers perform their military duties. Many urethane adhesive using dry coating method according to previous studies [2, 3] have been carried out to reduce the Table 1. One of specimens remained uncoated for frictional noise of coated fabrics and figured out tensile comparing to the treated specimens. Basic characteristics properties are one of important factors to control the of specimens are shown in Table Ⅱ. frictional noise. However, those studies considered only basic properties and mechanical properties (KES-FB) but have not considered coating conditions of the fabrics. Table Ⅱ. Basic characteristics of specimen Fiber Fabric Density The objectives of this study are to suggest the optimum Yarn T W Specimen Comp- constr- (w x coating conditions using the breathable waterproof type (mm) (g/m²) osition uction f/inch) fabrics coated in lab-scale, and to analyze the relationship uncoated 0.34 224.6 between frictional sounds and tensile properties of the #1 0.34 238.2 fabrics for minimizing fabric frictional sound of Korean #2 0.30 253.5 military combat uniform fabrics. #3 64/36 0.29 238.5 #4 Polyeste 0.32 257.4 Staple Plain 65 × 60 APPROACH #5 r 0.32 239.8 Experimental design #6 /Rayon 0.34 284.4 The first approach is to investigate the optimum #7 0.31 246.4 breathable water proof coating conditions for minimizing #8 0.32 251.2 fabric frictional sound using Response surface #9 0.34 250.5 methodology (RSM). Concentration of polyurethane based agent (X1: 60, 65, 70, 75, 80%) and curing Recording fabric frictional sound temperature (X2: 135, 140, 145, 150, 155°C) were chosen Fabric sounds were generated on a Simulator for as the independent variables of the central composite Frictional Sound of Fabrics (Patent, No. 10-015524) with design (CCD) (Table Ι) and the dependent variable were the speed of 0.6m/s in a soundproof room. The generated Sound Pressure Level (Y1), Water resistance (Y2), Water sounds of fabrics were recorded by using a microphone vapor transmission (Y3), Tensile stress at break (Y4), (Type 4190, B&K), and analyzed by a Pulse system Tensile strain at break (Y5). To optimize the dependent (Type 7700, B&K). variable, desirability function was defined as SPL (Y) = minimum. Breathable waterproof performance tests The second approach focuses on the relation between SPL To evaluate the breathable waterproof performance of the and tensile properties of fabrics using Pearson’s specimens, water resistance and water vapor transmission correlation. All data were analyzed using the SAS 9.1. tests were conducted by KS K ISO 881(Hydrostatic pressure test) and KS K 0594(Potassium acetated method). Table Ι. The central composite for optimization of coating conditions for minimizing fabric frictional sound Tensile property measurements Experiment Tensile properties were measured using INSTRON (CRE Concentration (X1) Temperature (X2) (specimen) type) under the standard condition (temperature 20°C; Code % Code °C NO. humidity 65%). All the reported results were the average #1 -1 65 -1 140 #2 1 75 -1 140 of five measurements. #3 -1 65 1 150 RESULTS AND DISCUSSION #3 74.48 31.24 SPL and breathable waterproof performances #4 74.50 31.33 #5 71.03 31.58 Table Ⅲ shows the SPL and breathable waterproof #6 69.57 29.85 #7 71.72 32.02 performances of specimens. All coated fabrics had a #8 75.12 32.10 higher SPL value than uncoated fabric. It demonstrates #9 74.40 32.11 that waterproof coating causes fabric frictional sound to be louder. The results of water breathable waterproof Relations between SPL and tensile properties performance tests indicated that coated fabrics used in this The relations between SPL and tensile properties are study have breathable waterproof function. reported in Table Ⅵ. It can be obtained that only tensile

stress at break was highly related to SPL (r=0.780). Table Ⅲ. SPL and breathable waterproof performances Therefore, controlling specimens’ tensile stress at break is Breathable waterproof performance a key point for minimizing fabric frictional sound. SPL Water vapor Specimen Water resistance (dB) transmission (mmH O) 2 (g/m2·24h) TableⅥ. Correlation coefficients of SPL and tensile uncoated 70.5 0 213302 #1 83.7 3030 6458 properties #2 72.5 4765 4507 SPL #3 78.5 2970 4943 Tensile stress at break .780* #4 80.5 2090 4756 Tensile strain at break -.232 #5 73.8 3480 5827 * : <.05 #6 73.6 9500 5471 #7 76.0 5920 7328 CONCLUSION #8 87.5 3330 5860 In this study, the optimum breathable waterproof coating #9 77.0 5930 9907 conditions of combat uniform were suggested. Minimum Prediction of optimum coating conditions and SPL was 66.69dB at concentration of 78.26% and predicted values 139.38°C of curing temperature. However, the predicted The optimum coating conditions for minimizing fabric breathable waterproof performance in the condition was frictional sound and predicted values of response relatively low compared to experimental results. Also, from the relationship between SPL and tensile variables are shown in Table Ⅳ. Minimum SPL (Y1) was properties, the sounds of the breathable waterproof fabrics 66.69dB at 78.26% in concentration of polyurethane can be minimized by controlling the fabrics’ tensile agent (X1) and 139.38°C in curing temperature (X2). property such as tensile stress at break. In this coating condition, however, predicted breathable The results of this study could be used as the preliminary waterproof performance (Y2, Y3) and tensile performance data for manufacturing breathable waterproof military (Y4, Y5) were relatively low. combat uniform fabrics which make minimum fabric frictional sound. Table Ⅳ. The optimum coating conditions for minimizing The predicted optimum coating condition was slightly out of the center of region of interest. In the future study, fabric frictional sound and predicted values of response therefore, new treatment condition ranges of central variables Independent composite design matrix are required for the reliability. Response variables2) variables1) X1 X2 Y1 Y2 Y3 Y4 Y5 ACKNOWLEDGMENT 78.26 139.38 66.69 4724.36 5809.72 67.36 30.67 This work was supported by the National Research 1) X1: Concentration (%); X2: Temperature (°C) Foundation of Korea (NRF) grant funded by the Korea 2) Y1:SPL (dB); Y2: Water resistance (mmH2O); Y3: Water vapor 2 2 government (MEST) (NO.2012-0005501). transmission (g/m ·24h); Y4: Tensile stress at break (N/mm ); Y5: Tensile strain at break (%) REFERENCES Tensile properties [1] D. P. Bishop, 1996, Fabrics: Sensory and Mechanical Properties, Textile Progress, Manchester. Table indicates the tensile stress and strain at break. The Ⅴ [2] C. Kim, Y. Yang, and G. Cho, “characteristics of coated fabrics resulted in a significant increase in stress sounds of generated from vapor permeable water repellent and strain at break. In case of specimen #8, the stress at Fabrics by Low-speed Friction”, Fibers and Polymers, break was increased by more than 25% and the strain at 2008, 9(5) p.639-645. break was increased by more than 27%. [3] Y. yang, M. Park, G. Cho, “Relationship between frictional sounds and Mechanical Properties of Vapor TableⅤ. Tensile strength and strain at break of specimen Permeable Water Repellent Fabrics for Active Wear”, Tensile stress at break Tensile strain at break Journal of Korea society for clothing industry, 2008, 10(4) Specimen (N/mm2) (%) p. 556-571. untreated 59.95 25.10 #1 74.64 29.95 #2 65.63 30.16 Textile Functional Coloration to Offer Photo-Induced Surface Functions

Jingyuan Zhuo, Ning Liu, and Gang Sun Fiber and Polymer Sciences, University of California-Davis, USA [email protected]

INTRODUCTION Similar to titanium dioxide (TiO2) nanoparticles, several anthraquinone compounds could provide photo-induced reactive functions under UVA or white light irradiation exposure [1-5]. These functions of the compounds attribute to photo- activation of anthraquinone rings to excited states and productions of radicals after hydrogen abstraction from media (Schemes 1 and 2). These radicals can initiate radical graft polymerization if they are formed on polymer chains, and formation of excited reactive oxygen species including singlet oxygen, superoxide radicals, and hydroxyl radicals (ROS) in the system. The ROS could also form hydrogen Scheme 2. Continuation of the mechanism [2] peroxide in water, a known disinfectant widely employed in inactivating pathogenic microorganisms Photo-active functions of anthraquinone and degrading other chemicals [5]. compounds In order to demonstrate the photo-active Scheme 1 shows the photo-chemical reaction functions of anthraquinone compounds incorporated mechanism of anthraquinone compounds. Under light on textiles fibers, radical graft modification of fiber irradiation, AQS can be excited to singlet status and surfaces, photo-polishing of wool scales, then the singlet goes through intersystem crossing to decolorization of other colorants, and self- its triplet status due to close energy level of two decontamination functions, induced by the statuses of anthraquinone structures (Equation 1). anthraquinone derivatives will be reviewed in this The triplet AQS can collide with triplet oxygen in air presentation. Several anthraquinone compounds, to produce singlet oxygen and ground state AQS including sodium 2-anthraquinone sulfonate (2-AQS), (Equation 2), and also can behave like a bi-radical on disodium 2,6-dianthraquinone sulfonate (2,6-AQS), the carbonyl group. The oxygen radical will abstract and 2-anthraquinone carboxylic acid (2-AQC), were a hydrogen atom from a donor. The hydrogen donor incorporated onto fibers and textiles. Structures of could be a weak C-H or N-H bond from polymer or a the modified fabrics were confirmed by Fourier solvent. Thus, AQS radical and a polymer or solvent Transform Infrared (FTIR) spectra data and radical (R•) will be resulted (Equation 3). antimicrobial functions against both gram negative and gram positive bacteria are presented as well. The AQS radical (on carbon atom, see Scheme 2 dye radical) could react with triplet oxygen (O2) to produce peroxide structure, which could lead to formation of many reactive oxygen species such as hydroxyl radicals and superoxide, as well as hydrogen peroxide with existence of water (Scheme 2).

Applications: Radical graft polymerization on AQS dyed fabrics According to the mechanism of photo-induced reactions on anthraquinone structures, one of the reaction paths (Equation 3) can lead to generation of polymer radicals (R•), which can initiate radical graft polymerizations on the polymer if a vinyl monomer Scheme 1. Proposed photo-reaction mechanism[2] exists in the system. As an example, 2-AQS dyed nylon fabrics were utilized in a photo-induced radical graft polymerization of acrylic acid onto the fabrics. Applications: Removal of scales on AQS dyed The nylon fabrics dyed with 1.5% 2-AQS (owf) were wool fibers dipped into monomer solutions with acrylic acid Anthraquinone dyed wool fabrics could produce concentration varied from 2% to 30 %. The fabrics ROS such as hydrogen peroxide under light exposure. were padded and then exposure to UVA (365 nm) The ROS could have some destructive effects on light for 2 hours. The treated fabrics were thoroughly surfaces of the wool fibers. Figure 2 shows SEM washed and measured, Figure 1 shows the degree of images of the AQS dyed wool fibers after exposing to grafting on the fabrics versus the concentration of the UVA for extended time. As light exposure time monomer in the finishing baths. First, the grafting increased the scales of the wool fibers were gradually reaction was successful with the dye as photo- removed. initiator on dyed nylon fibers. The grafting yields increased with the increase of monomer A B concentrations in the finishing baths, suggesting possible formation of longer side chains with high concentration of monomers in finishing baths.

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6

5

4 Degree of Grafting (%) Grafting of Degree 3 Figure 2. SEM images of dyed wool fiber. (A) The 2 5 1015202530 one before UV irradiation. (B) Wool fiber after 6 hr Monomer Concentration (% (w/v)) UV exposure. (C) Wool fiber after 8 hr UV exposure. (D) Wool fiber after 36 hr UV exposure. Figure 1. Degree of grafting versus acrylic acid concentration (2%, 4%, 6%, 8, 16%, 30% w/v), UVA exposure time 2hrs, 2-AQS concentration 1.5 wt%. [2] CONCLUSIONS Anthraquinone compounds could be excited by Applications: Antimicrobial functions of AQS UVA and white light to produce reactive oxygen finished fabrics species on surfaces of textile fibers. The Since anthraquinone compounds could produce anthraquinone treated fabrics exhibited photo- hydroxyl radicals, singlet hydrogen, and even induced radical graft polymerization, bactericidal hydrogen peroxide so-called reactive oxygen species activities against both S. aureas and E. coli, and (ROS) on the surfaces of the dyed fabrics. ROS can surface polishing functions under UVA irradiation. kill bacteria easily. As an example of demonstrating such antibacterial functions, 2-anthraquinone REFERENCES carboxylic acid (2-AQC) treated cotton fabrics could 1. Liu, Ning and Gang Sun, ACS Applied Materials provide 99.99% reduction rate against E. coli & Interfaces, 3 (4), 2011, pp 1221–1227. bacterium even for the cotton treated with the lowest 2. Liu, Ning and Gang Sun, Industrial and 2-AQC concentration. The reduction of S. aureus was Engineering Chemistry Research, 50 (9), 2011, about 99-99.9% depending on the concentration of pp 5326–5333. the compound in the finishing baths. Overall, the test 3. Liu, Ning and Gang Sun, Dyes and Pigments. 91. results indicated that the 2-AQC treated cotton 2011, 215-224. possessed excellent photo-induced biocidal functions. 4. Liu, Ning and Gang Sun, AATCC Review. 2011, Vol. 11. No. 5. 2011, Sept/Oct. p 56-61. Liu, Ning, Gang Sun, and Jing Zhu, Journal of Materials Chemistry, 21, 2011, 15383–15390.

Comparison of Color Properties of CO2 Laser-Treated Cotton Polyester-Blended Fabric Before and After Dyeing

O.N. Hung, C.K. Chan C.W. Kan, and C.W.M. Yuen Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China [email protected]

Keywords: Color, CO2 laser, Cotton, Polyester peak at wavelength of 450-490nm which indicated that laser treatment has no influence on chromaticity change ABSTRACT of the samples. Cotton polyester blended fabrics were treated by CO2 laser before and after dyeing with reactive dye under When reflectance curves of samples treated with two different laser parameters. Color properties included approaches were compared, curves of fabrics treated with reflectance, K/S sum and CIEL*a*b* of treated fabrics laser then dyed (L/D) were at higher positions than the were evaluated through spectrophotometer. other one (D/L). This indicated that samples treated with L/D approach had lighter surface appearances than D/L INTRODUCTION approach. CO2 laser being as a dry treatment with advantages such as short treatment time and high precision [1] have drawn Color yield which is indicated by K/S sum value of the attention of many researchers. Due to the small samples also revealed similar results as the reflectance amount of study considering the influence of laser on value with D/L approach shower a higher K/S sum value dyeing properties of blended fabrics, in this study, and thus, better color yield than the L/D approach. different combinations of laser parameters were applied on cotton polyester blended twill fabric using two CIEL*a*b* measurement approaches, before and after dyeing with reactive dye in When comparing L* values of two samples, the result blue 1% concentration. Color properties which include revealed that laser treated then dyed samples (L/D) had reflectance, color yield (in terms of K/S value) and CIE higher L* values than dyed then laser treated samples L*, a* and b* values of samples treated with different (D/L) which is equivalent to the result of reflectance approaches are compared and evaluated. values and K/S sum values.

EXPERIMENTAL From the results of CIE a* and b* values, when Materials comparing two samples, samples dyed then laser treated 60% cotton blended with 40% polyester twill fabrics were (D/L) were found to be greener and less bluish than laser used. treated then dyed samples (L/D).

Laser treatment CONCLUSION The laser treatment was conducted by a CO2 source laser In this paper, color properties of cotton polyester engraving machine. blended samples treated with different laser and dyeing approaches were studied. In comparison of these two Dyeing samples, dyed then laser treated (D/L) samples had darker Remazol Brilliant Blue R reactive dye was used in the color, more greenish and less bluish than laser treated dyeing process. than dyed samples (L/D).

Approaches ACKNOWLEDGMENT Laser treated then Dyed (L/D) The authors would like to thank for the financial support Dyed then laser treated (D/L) from the department of Institute of Textiles and Clothing in the Hong Kong Polytechnic University. Evaluation The color measurement of the fabric samples were REFERENCE evaluated using a spectrophotometer under light source of F. Ferrero and F. Testore, Autex Res. J., 2(3), 109 (2002). illuminant D65 and with a 10o observer.

RESULTS AND DISCUSSION Color measurement According to the result of reflectance value, fabrics treated with two approaches revealed similar reflectance curves. The reflectance curves of both samples had the Development of a Novel Bicomponent Fiber-Based PET/PE Composite with Improved Interface and Mechanical Performance

Mehmet Dasdemir1, Benoit Maze2, Nagendra Anantharamaiah3, and Behnam Pourdeyhimi2 1Textile Engineering Department, University of Gaziantep, Gaziantep, 27310 Turkey 2The Nonwovens Institute, North Carolina State University, Raleigh, NC, 27695 USA 3Hollingsworth & Vose Company, Floyd, VA, 24091 USA [email protected]

STATEMENT OF PURPOSE The schematic representation of possible in-situ reactive The purpose of this study is to develop a novel compatibilization in bicomponent fiber structure is shown bicomponent fiber based Poly(ethylene terephthalate) in Figure 1. In this approach, the functional group of the (PET)/polyethylene (PE) composite with improved compatibilizer reacts with the terminal groups of the core mechanical performance by enhancing the adhesion at the polymer (PET) and form block copolymer at the interface. interface of PET and PE. At the same time, ethylene blocks of the compatibilizer interact or even entangle with the sheath polymer (PE) INTRODUCTION and anchor this phase. PET and PE are the most commonly used polymers and are exploited in many applications such as fibers, films, After Reactive and textiles. One of the other important application areas Compatibilization for these polymers is bicomponent fibers and nonwovens in which PET/PE polymer configuration provides PE economical advantage and combines important Compatibilizer characteristics of each polymer. Similarly, thermoplastic composites made from these materials can utilize from these advantages and can be a good and inexpensive HO –PET–COOH alternative for conventional thermoplastic composites [1]. Hydroxyl Carboxyl In such composite, PET fiber offers good mechanical properties, while PE matrix provides excellent impact PET-g-Compatibilizer Bicomponent Fiber properties and resistance to chemicals and environmental (Core/Sheath) conditions. However these two polymers are Cross-section thermodynamically immiscible, so the composite material Figure 1: Schematic representation of the possible in-situ consisting of these two polymers is expected to have high reactive compatibilization between terminal group of PET interfacial tension and weak adhesion. This problem also and functional group of compatibilizer in bicomponent arises for PET/PE bicomponent fiber structures [2] and fiber. nonwoven based thermoplastic composites made from these materials [1] and usually leads to phase separation PET/PE bicomponent fibers and nonwovens were at the interface. Therefore, the tensile properties of these produced with the addition of different amount of materials can exhibit poor performance as a result of the compatibilizers (into the sheath component) in fiber inefficient load transfer between two components. spinning stage. Compatibilization was performed during composite fabrication stage using different processing APPROACH temperatures. Tensile properties of the compatibilized Our main objective in this study is to enhance the composites and morphological analysis of the fractured adhesion at the interface of PET/PE in order to improve surfaces were recorded and compared with control the mechanical performance of bicomponent fiber based nonwoven composites. thermoplastic composites. For this purpose, commercially available Ethylene-ethylene acrylate-glycidyl RESULTS AND DISCUSSION methacrylate with 5 wt% (E-EA-GMA5) and 9 wt% (E- The tensile responses of PET/PE composites were EA-GMA9) GMA contents and a maleic anhydride significantly improved with the addition of functionalized (2 wt%) triblock copolymer of styrene and compatibilizers. The best overall tensile properties were ethylene/butylene (SEBS-g-MA2) were chosen as obtained for the composites including 2 wt% of SEBS-g- compatibilizers to promote adhesion between PET and MA2 (see Figure 2). PE.

60 Control

40

Control Stress (MPa) 20 2 wt% 5 wt% 10 wt%

0 0481216 Strain (%) 20 µm (a) Figure 2: Stress-strain graphs of PET/PE (control) and PET/PE+SEBS-g-MA2 nonwoven composites with varying compatibilizer content [3] E-EA-GMA5

The effect of compatibilization on the fracture behavior of composites was shown in Figure 3. It is clearly seen that the surfaces of PET (reinforcement) fibers are mostly free of matrix in control sample. This indicates that the fracture occurred in the form of fiber pull-out. Such kind of failure is typically observed for weak interfaces. On the other hand, when the fractured surfaces of other composites including E-EA-GMA5 as a compatibilizer were investigated, we observed that matrix polymer adhered to PET better and therefore the fracture mode shifted to cohesive failure. The characterization of the fracture surfaces allowed us to provide the evidence of 20 µm enhanced adhesion between matrix polymer and (b) reinforcement fiber for the composites including compatibilizers. Therefore, we can conclude that the Figure 3: SEM micrographs of the fractured surface of reactive compatibilization was achieved during composite tensile test samples: (a) Control and (b) E-EA-GMA5 fabrication stage and improved the adhesion in PET/PE resulting in a better load transfer and enhanced REFERENCES mechanical properties. [1] Dasdemir M, Maze B, Anantharamaiah N, Pourdeyhimi B. “Formation of novel thermoplastic CONCLUSIONS composites using bicomponent nonwovens as a This study shows that mechanical performance of novel precursor.” J Mater Sci 2011;46(10):3269-3281. PET/PE composites can be improved with the [2] Dasdemir M, Maze B, Anantharamaiah N, incorporation of SEBS-g-MA and E-EA-GMA into the Pourdeyhimi B. Influence of Polymer Type, Composition sheath component of fiber and careful selection of and Interface on the Structural and Mechanical Properties compatibilizer content and compatibilization temperature. of Core/Sheath Type Bicomponent Nonwoven Fibers”, J Mater Sci 2012;47(16):5955-5969. ACKNOWLEDGEMENT [3] Dasdemir M, Maze B, Anantharamaiah N, The Nonwovens Institute is gratefully acknowledged for Pourdeyhimi B. “Reactive Compatibilization of providing financial support for this work. Poly(ethylene Terepthalate)/ Polyethylene Nonwoven Based Thermoplastic Composites”, Comp Sci Tech 2012, Under Review.

Fiber Processing

SiC Fiber Made with Aqueous Binder by Melt Spinning (United Materials Technologies Process)

Alex Lobovsky and Mohammad Behi United Materials Technologies, LLC 211 Warren St, Newark, NJ 07103 [email protected]

Presently commercially available SiC fiber costs The fiber could be spin with various cross-sectional upward of $1000 /kg and is produced abroad. The shapes. The feedstock material is 100% re-useable high cost of fiber prevents its use in products. This and environmentally friendly. is especially true for military applications, which in addition to low cost, require domestically produced fiber. UMT developed aqueous SiC feedstock material for economical fiber melt spinning process. The feedstock utilizes our proprietary water based binder technology. First SiC powder is mixed with UMT binder, creating feedstock with the right mix of visco-elastic properties. Using conventional polymer fiber spinning equipment SiC fiber is melt spun at low - 80C - temperature. Just like a melt spinnable polymer fiber, it can be stretched, coated and wound on bobbins. The final step is sintering of the fiber. The binder system could be adopted for wide range of ceramics, metals and composite materials. Melt spun alumina, zirconia, strontium titanate, tungsten/20 copper and stainless steel fibers were demonstrated.

Examples of some of the spun fiber x-sections

UMT melt spun, sintered SiC Fiber, density=3

High-Performance Polyimide Fibers Prepared by Dry Spinning Technology

Qinghua Zhang, Yuan Xu, Jie Dong, Chaoqing Yin, Shihua Wang, Dajun Chen State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, People’s Republic of China [email protected]

ABSTRACT Spinning solution Polyimide fibers exhibit many valuable properties such as Pump outstanding thermal stability, chemical resistance, and Spinneret good resistance to irradiation. Here, we report one of method to produce polyimide fibers in large scale. The Hot air precursor fibers were prepared via dry-spinning process from poly(amic acid) solution, and then the polyimide fibers were produced by cyclization reaction and drawing Precursor fibers process. The fibers exhibit good mechanical properties and excellent thermal stability. The structure homogeneity Hot air of the fiber was significantly improved by heat-drawn stage. FTIR, TGA, DMA, SEM and WAXD were used to characterize the structures and properties of the fiber. Hot air

Keywords: polyimide fiber, dry-spinning Take up roll

INTRODUCTION Figure 1. Schematic presentation of dry-spinning process As one type of high performance fibers, polyimide fibers possesses great application prospect in spaceflight field, APPROACH defense construction, high speed transportation vehicles, Poly(amic acid) solution was synthesized by dissolving ocean exploitation, and environment protection due to its ODA in dimethylacetamide (DMAc) followed by the outstanding thermal and radiation stability, and excellent addition of equimolar amount of PMDA gradually. The mechanical properties. [1-3] precursor solution was pushed into a heating column with flow air hot, and immediate vaporization of DMAc Polyimide fibers can be prepared by one-step or two-step resulted in the formation of as-spun PAA fibers. Then, processing methods. [4-7] In one-step method, the polyimide fiber was obtained by heating the as-spun polyimide solution in m-cresol or p-chlorophenol is used fibers under a drawing ratio of 2.0 through a heating tube to prepare the fibers via wet-spinning or dry-jet-wet at 350 oC and subsequently through another tube at 400 spinning. In two-step process, the precursor, poly(amic oC. The structures and properties were measured. acid) (PAA) solution in DMF or DMAC, is used to prepare PAA fibers, and then the precursor fibers are in RESULTS AND DISCUSSION situ transformed to the corresponding polyimide fibers by Mechanical properties chemical or thermal cyclization reaction. The mechanical properties of heat-drawn polyimide fibers are listed in Table 1. Stretch has an influence on the Dry-spinning technology of polyimide fibers is a two-step mechanical properties. Tensile and modulus range from process, as shown in Figure 1, in which the precursor 2.7 cN/dtex to 7.1 cN/dtex and 248 cN/dtex to 493 fibers are produced via spinning the PAA solution into a cN/dtex, respectively. heating column and followed solvent vaporization. The precursor fibers are transformed into polyimide fibers by Table 1. Mechanical properties of the PI fiber heat treatment. [8.9] Strength Elongation Modulus Drawn ratio (cN/dtex) (%) (cN/dtex) The aim of our work is to prepare a high performance λ=1.6 2.7 22.7 248 polyimide fiber dry-spinning process, using relatively λ=2.2 6.1 18.4 394 cheap monomers such as 1,2,4,5-benzenetetracaboxylic anhydride (PMDA) and 4, 4’-diamnodiphenyl ether λ=2.8 7.1 11.2 493 (ODA). Compared to wet-spinning or dry-jet wet- spinning, dry-spinning process is a high efficient method By varying thermal treatment temperature, we can obtain and the solvent is easily recovered, even though machine the various fibers with different mechanical properties. and technology of the method is complex. Generally, high thermal treatment temperature along with high drawn ratio leads to a significant improvement in the shows clear diffraction arcs (pattern c), indicating that the mechanical properties. crystallization occurs in the fibers, along with the orientation of the crystals. Thermal stability The TGA curves of the fibers display excellent thermal stability, as shown in Figure 2. The 5% weight loss temperatures of the PI fibers under air and nitrogen are up to 593 oC and 598 oC, respectively. The 55%-60% of the original mass at N2 retains even after heating to 800 °C, which is a high carbon yield for this material.

100 o (a) (b) 550 C 80 Figure 4. Cross-section of (a) PAA fibers and (b) heat- N 2 drawn PI fiber 60

40 Weight (%) Weight 20 Air

0 200 300 400 500 600 700 800 Temperature (oC)

Figure 2. TGA curves of PI fiber a b c

The DMA cure of heat-drawn PI fiber is investigated Figure 5. 2D WAXD patterns of (a) PAA fiber, (b) PI from room temperature up to 550 °C, with the results fiber and (c) heat-drawn PI fiber. presented in Figure 3. The storage modulus E′ of the fiber exhibits maximum value and excellent retention in the CONCLUSIONS applied range of temperature. An obvious transition is High performance polyimide fibers can be prepared via seen on the loss modulus E″ curves at about 460°C, which dry-spinning process, and this process is a promising is generally regarded as glass transition temperature (Tg). technology for realizing industrial revel production of polyimide fibers. 10 0.16 Storage Modulus 0.14 0.12 ACKNOWLEDGMENT 1 0.1 This work is financially supported by NSFC (51233001,

0.08 Delta tan 51173024, 50873021), 863 plan (2012AA03A211), and Loss Modulus 0.1 0.06 Shuguang Plan (09SG30).

0.04 0.01 tan Delta REFERENCES 1. Zhang, Q.; Dai, M.; Ding, M.; Chen, D.; Gao, L. Euro. 1E-3 Polym. J. 2004, 40, 2487-2493. Storage and Loss Modulus (N/tex) Modulus Loss and Storage 100 200 300 400 500 2. Zhang, Q.; Dai, M.; Ding, M.; Chen, D; Gao, L. J. Appl. Temperature (oC) Polym. Sci. 2004, 93, 669-675. Figure 3. DMA curves of PI fiber 3. Liu, J.; Xia, Q.; Dong, J.; Xu, Q.; Zhang, Q. Polym. Degrad. Stab. 2012, 97, 987–994. Morphology and WAXD patterns of PI fiber 4. Kotera, M.; Nishino, T.; Nakamae, K. Polymer 2000, The morphology of the fibers can be observed by 41, 3615-3619. scanning electron microscopy (SEM), as shown in Figure 5. Eashoo, M.; Shen, D.; Wu, Z.; Lee, C. J.; Harris, F. W.; 4. As for PAA fiber in the image (a), the cross-section of Cheng, S. Z. D.. Polymer 1993, 34, 3209-3215. the fiber is oval and less voids; whereas, the fibers 6. Jin, L.; Zhang, Q.; Xu, Y.; Chen, J. European Polymer become round cross-section shown in image (b). Drawing Journal 2009, 45, 2805-2811. process or heat treatment reduces defect, voids, for 7. Park, S. K.; Farris, R. J. Polymer 2001, 42, 10087- instance, and results in the dense microstructure. 10093. 8. Irwin, R. S. US Patent 3415782, 1968; and US Patent WAXD can be used to measure the aggregation state of 4640972, 1987. polymers. Apparently, the precursor fiber exhibits the 9. Deng, G.; Zhang, Q.; Xu, Y.; Chen, D. J. Appl. Polym. obvious amorphous state, as shown in Figure 5 (a). The Sci. 2009, 113, 3059-3067. un-drawn polyimide fiber also gives amorphous structure (pattern b). However, the WAXD of the drawn fiber

High-Throughput Needleless Electrospinning of Core-Sheath Fibers

Xuri Yan1, Quynh Pham1, John Marini1, Robert Mulligan1, Upma Sharma1, Michael Brenner2, Gregory Rutledge3, and Toby Freyman1 1Arsenal Medical, Inc., Watertown, MA, USA; 2School of Engineering and Applied Science, Harvard University, Cambridge, MA, USA; 3Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA [email protected]

OBJECTIVE RESULTS AND DISCUSSION Develop a high-throughput electrospinning process for the Similar to a coaxial needle (which provides a single point manufacturing of core-sheath fibers. for polymer solutions to exit), the slits of the needleless electrospinning fixture provides a line along which INTRODUCTION polymer solutions can exit and co-localize (“one- Core-sheath fibers fabricated via electrospinning show dimensional” electrospinning). Upon application of a great promise for use in a variety of applications critical electric field strength, multiple jets initiate along including drug delivery/tissue engineering [1], self- the length of the slit-surface as shown in Figure 2A. As healing coatings [2], filters [3], and super-hydrophobic the core and sheath solutions exit from their respective materials[4]. However, needle-based, core-sheath slits, they co-localize to form multiple core-sheath Taylor electrospinning systems typically operate at flow rates cones spontaneously that ultimately leads to core-sheath between 1-10 ml/h, resulting in low throughput and fibers (Figure 2B-D). This process occurs within a few deposition rate. Various groups have addressed this seconds and starts with the formation of an limitation by developing high throughput methods using electrospinning jet composed of the sheath polymer only multi-nozzles or through free liquid surface (Figure 2B). We hypothesize that the internal fluid electrospinning, such as the Nanospider® developed by pressure will drop at the locations where sheath solution Elmarco [5, 6]; however, these methods are currently jets are present. As a result, the inner core solution will applicable only to monofibers. We have developed a preferentially flow towards locations with lower relative novel electrospinning fixture capable of producing core- pressure. Ultimately, we hypothesize that viscous shear sheath fibers with up to 300-fold increase in volumetric forces of the sheath solution entrain the core solution to throughput relative to typical needle approaches. This form a stable core-sheath Taylor cone (Figure 2D). significant achievement in manufacturing rate will help realize the tremendous potential of core-sheath fibers.

EXPERIMENTAL The high-throughput, needleless electrospining fixture consists of two triangular shaped troughs that are aligned to a single vertical plane to form a slit-surface (Figure 1). The core slit is set to be slightly below that of the sheath

slit. Core and sheath Figure 2. (A) Example of multiple electrospinning jets formed Figure 1. One-dimensional core and across a slit-surface. (B) Electrospinning jet formed from sheath sheath slit-surface formed from polymer solutions are solution without core solution entrainment. (C) Same aligning two fixtures each delivered to the slits electrospinning jet as in (B), demonstrating the spontaneous containing a length-wise slit. through their respective entrainment of core solution. (D) Fully formed electrospinning jet fixtures by applying precise control of pneumatic pressure exhibiting a core-sheath structure. using syringe pumps, ensuring consistent flow rates. The Using this needle-less fixture, we have been able to fixture itself is connected to a high voltage source for operate at total flow rates up to 300 ml/h - an order of generation of an electric field. We performed experiments magnitude higher than our electrospinning using a needle- to evaluate the effects of (1) solution flow rates and (2) based system. Furthermore, preliminary data indicate that solution viscosity on the formation of core-sheath Taylor the system is scalable, thereby increasing throughput even cones. Table I details the polymer systems used in the further. To the best of our knowledge, the data presented experiments. here represent the first time that core-sheath fibers have

Table I. Details of polymer systems used in the study been electrospun at such high volumes. The diameter of the core-sheath fibers produced using the polymer Experiment 1 Experiment 2 systems listed in Table I were around 2-4 micron, which Sheath 3.5wt% PLGA in 12 or 16wt% PCL in is similar in range to what is achieved with a core/sheath Solution hexafluoroisopropanol chloroform: methanol Core 12wt% PCL in 6:1 (by vol) chloroform:methanol needle-based systems. An example of the fibers produced Solution containing 30% dexamethasone relative to PCL along with a cross-sectional image showing the core- sheath structure is shown in Figure 3. We next performed a series of studies to identify and understand the variables suggest that control over core-sheath Taylor cone and conditions under which core-sheath Taylor cones structure can be manipulated via flow velocities of the form using our novel fixture design. solutions. Solution viscosity. The impact of solution viscosity on core-sheath Taylor cone formation was also investigated. As shown in Table I, either a 12wt% or 16wt% PCL solution was used as the sheath solution, resulting in differences in viscosity of 280 cP vs. 760 cP, respectively. The viscosity of the core solution was 500 cP. In this experiment, the flow rates for both systems were set at 200 and 20 ml/h for the sheath and core solutions, respectively. It was found that the core-sheath formation and morphology of the Taylor cones was more distinct when 16wt% PCL was used as the sheath solution, even though the same flow rates were used. We hypothesize that this results from a shear force sufficient to entrain the core solution due to a sheath solution viscosity higher Figure 3. (A) Scanning electron micrograph of core-sheath fibers than the core solution viscosity (760 > 500 cP). In fabricated using needle-less fixture. (B) Low magnification cross- contrast, the 12wt% PCL solution has a viscosity lower sectional image of multiple fibers showing core-sheath structure (white arrows). (C-D) High magnification image of fiber cross-section showing than that of the core solution (280 < 500cP) and did not distinct crystalline drug core (white arrow) enclosed by sheath polymer. exhibit distinct core-sheath Taylor cone formation. The data here indicate that flow velocity is not the only factor Solution flow rate. The effect of solution flow rate on that determines whether core/sheath Taylor cones form, core-sheath Taylor cone formation was investigated by but that solution viscosities also play a role (Note: The (1) keeping the sheath flow rate constant while varying conditions shown here meet the conditions of sheath flow the core flow rate and (2) keeping the core flow rate velocity being greater than core flow velocity as described constant while varying the sheath flow rate. For the first in the previous section). experiment, the sheath flow rate was kept constant at 200 ml/h while varying the core flow rate to 20, 40, and 60 ml/h. As shown in Figure 4A-C, distinct core-sheath Taylor cones could be visualized only when the core flow rate was set to 40 or 20 ml/h (Figure 4A, B). The conditions with successful core-sheath Taylor cone formation corresponded to when the calculated total solution (core + sheath) flow velocity exiting the top of Figure 5. Images of distinct and non-distinct core/sheath Taylor cones the slit was greater than the core solution flow velocity. using sheath solutions of different viscosities. Solid and dashed border Moreover, a greater difference between these two values indicates distinct or non-distinct core/sheath Taylor cones, respectively. resulted in a more distinct core-sheath structure. For the second study, the sheath flow rate was varied to CONCLUSION 200, 100, or 40 ml/h while the core flow rate was kept We have developed a novel needle-less electrospinning constant at 20 ml/h (Figure 4 D-F). The results for this set fixture capable of producing core-sheath fibers at high of experiments were similar to before; specifically, throughput levels. Solution velocity and viscosity are two distinct core-sheath Taylor cones formed only when the important parameters that can be manipulated to obtain total solution velocity was greater than the core velocity. multiple core-sheath Taylor cones, jets and electrospun This condition was true when the sheath flow rate was set fibers. This technology has the potential to address the at 100 ml/h or above (Figure 4 D, E). These results current industrial manufacturing limitations for the production of core-sheath fibers.

ACKNOWLEDGMENT This work was performed under the support of the U.S. Department of Commerce, National Institute of Standards and Technology, Technology Innovation Program, Cooperative Agreement #70NANB11H004.

BIBLIOGRAPHIC REFERENCES 1. Meinel, A.J., et al. Eur J Pharm and Biopharm, 2012. 81(1): p. 1-13. 2. Park, J.H. and P.V. Braun. Adv Mater, 2010. 22(4): p. 496-9. Figure 4. Example images of core/sheath Taylor cones from the flow 3. Moghe, A.K. and B.S. Gupta. Polym Rev, 2008. 48(2):p.353-377. rate study illustrating flow rate conditions in which distinct (solid 4. Han, D. and A.J. Steckl. Langmuir, 2009. 25(16): p. 9454-62. border) and non-distinct (dashed border) core/sheath Taylor cones were 5. Kumar, A., et al. Macro Mater Eng, 2010. 295(8): p. 701-708. formed. (A-C) Set of conditions in which the core flow rate was varied. 6. Petrik, S. and M. Maly. in Mater Res Soc Symp Proc. 2010. (D-E) Set of conditions in which the sheath flow rate was varied. Coaxial-Free Surface Electrospinning

Keith M. Forward1,2, Alexander Flores1, Gregory C. Rutledge1 1Department of Chemical Engineering, Massachusetts Institute of Technology 2Current address: Department of Chemical and Materials Engineering, California State Polytechnic University, Pomona, CA [email protected]

INTRODUCTION The production of electrospun nanofibers has gained increasing interest over the past years due to their unique properties such as high porosity, high surface area and small fiber diameters. Electrospun nanofibers have implications in a broad range of fields, for instance drug delivery, filtration, tissue engineering, nanocomposites, textiles and alternative-energy generation systems such as solar cells, fuel cells, and energy storage devices [1]. Electrospun nanofibers with the core-shell (or core- sheath) morphology enjoy the same opportunities and Figure 1. Evolution of the surface profiles of the two applications as homogeneous nanofibers, but with several immiscible liquids as the wire (viewed end-on) travels additional advantages; these include the opportunity to through the liquid interfaces. engineer the core and shell of the fibers for different, complementary purposes (e.g. controlled release of pharmaceutical compounds), to produce fibers from immiscible solutions in a direction perpendicular to the otherwise unspinnable (e.g. low molecular weight) wire axes. The solutions are oriented such that as the wire materials, to remove the core in order to form hollow sweeps through the bath, the bottom solution becomes fibers, or to remove the shell in order to expose a entrained on the wire and the top solution becomes functional core. Conventional coaxial electrospinning is a entrained on the bottom solution that coats the wire. This simple technique that employs multi-centric needles to configuration leads to formation of an annular bilayer film produces core-shell fibers ranging from hundreds of on the wire, where the electrode is coated by the bottom nanometers to tens of microns in diameter. However, one solution and the bottom solution is coated by the top of the major drawbacks of conventional electrospinning solution. Figure 1 shows the development of the annular using needles or spinnerets is the limited productivity of bilayer film as the wire travels through the liquid bath. 0.001 to 0.1 g/h per nozzle (or orifice) [2]. Attempts to Control of the bilayer coating process depends sensitively develop multiple needle configurations have been on the relative capillary numbers, Ca = uη/γ (where u is unsuccessful in producing uniform mats and fibers. the velocity of the wire,  is the viscosity and γ is the Alterative system configurations have been investigated surface tension,) of the two solutions. where electrohydrodynamic (EHD) jets are formed from a free liquid surface instead of a confined geometry (the Due to a Plateau-Rayleigh instability, the annular bilayer spinneret). We refer to this technique as “free surface film subsequently breaks up into compound droplets such electrospinning” (also known as “needleless that each droplet on the metal wire consists of an inner electrospinning”). Free surface electrospinning from a part (the bottom solution) encapsulated within a fluid coated on a cylinder or wire electrode has been superficial layer of an outer liquid (the top solution). The shown to be capable of producing large quantities of solutions are designed so that the conductivity and electrospun fibers while maintaining uniformity in the dielectric constant of the bottom solution are greater than fiber diameter and electrospun mat [3]. Due to the nature those of the top solution. The differences in conductivity of EHD jets forming from a free liquid surface, it has and dielectric constant between the two fluids cause a proven difficult to produce core-shell electrospun buildup of free charge at the interface between the inner nanofibers by this method. However, by carefully and outer liquids of the compound droplet. At sufficiently engineering the system configuration and solution high local electric field, the individual droplets deform, properties, we have been able to produce core-shell fibers and the inner liquid jets through the outer liquid, by means of free surfaces electrospinning. producing a coating flow of the outer liquid (top solution) over the jetting inner liquid (bottom solution). As the jet APPROACH is directed upward due to the electric field, the solvents In this process, metal wire electrodes (typically 200 from the two solutions evaporate, causing the jet to microns in diameter) are mounted on a spindle and are solidify into a nanofiber where the core and shell consist drawn through an electrified liquid bath of two of the material from the bottom and top solutions, respectively. The nanofibers are collected on a grounded plate or conveyor . The spindle continuously rotates, successively sweeping the electrode(s) through the two 1 solutions to form the annular bilayer film, breakup of the bilayer film into compound droplets on the electrode, B 0.8 jetting of fluid from each droplet, and evaporation of ν solvent from the jet to form fibers with core-shell morphology arranged in a uniform electrospun mat on the 0.6 collection surface. 0.4 RESULTS AND DISCUSSION The efficacy of this process was demonstrated using

Volume fraction, fraction, Volume 0.2 aqueous solutions of polyethylene oxide (PEO) and organic solutions of polystyrene (PS) (in various solvents). The densities of the two solutions were 0 designed such that the bottom solution was the aqueous 0.001 0.01 0.1 1 phase and the top solution was the organic phase. This CaT/CaB configuration successfully produced core-shell nanofibers Figure 2. The volume fraction of the entrained solution as where the core and the shell consist of PEO and PS, a function of the ratio of capillary numbers of the two respectively, as shown in Figure 2. solutions. The symbols represent different solution compositions of the two solutions where the volume fraction was determined by UV-vis spectrometer. The dash line following the relation where h ~Cab, for the case where the wire is drawn horizontal (b = 0.22) to the free surface [2].

The capillary ratio, CaT/CaB (where CaT and CaB are the capillary numbers of the top and bottom solutions, respectively) of the two solutions was carefully chosen to control the coating process. As the capillary ratio goes to zero, the less viscous top solution drains off the surface of the bottom solution, resulting in the composition of the fibers consisting mainly of the polymeric material in the bottom solution. Alternatively, as the capillary ratio increases, greater amounts of top solution coat the bottom solution, increasing thickness of the shell layer. By the altering the capillary ratio, we show that it is possible to Figure 2. Scanning electron micrograph of coaxial free control the shell thickness of the fiber. surface electrospun fibers. The core filament is clearly evident in places where the shell has been broken. CONCLUSION

Electrospun fibers with the core-shell morphology have UV-Vis spectrometry was used to determine the mass been successfully produced by means of a free surface fraction of polystyrene, x , in the final PS-PEO core-shell T electrospinning technique. In addition, the shell thickness fibers. PS is UV active at a wavelength 260 nm, where is governed by the capillary ratio of the two solutions. PEO is not UV active. The PS-PEO fibers were dissolved This technology promises to allow for scale up and in dichloromethane (DCM) to perform the UV-Vis industrialization of the production of core-shell spectrometry. It is assumed that the composition of the nanofibers. core-shell fibers is representative of the entrained solution composition on the wire. REFERENCES

[1] A. K. Moghe and B. S. Gupta, “Co-axial It has been shown previously that the thickness of Electrospining for Nanofiber Structures: Preparation and entrained solution, h, depends on the capillary number of applications” Poly. Rev., 48 (2008) 353-377. the liquid, according to the following relation: h ~ Cab [2] S. A. Theron, E. Zussman, A. L. Yarin, “Experimental [3,4]. Using this relationship, it is possible to estimate the Investigation of the Governing Parameters in the volume fraction of the bottom solution relative to the total Electrospinning of Polymer Solutions.” Polymers, 45 entrained solution, ν , assuming that the entrainment on a B (2004) 2017-2030. liquid surface is similar that on a solid surface and the [3] K. M. Forward, and G. C. Rutledge, “Free Surface thickness of the entrained solution is less than the radius Electrospinning from a Wire Electrode” Chem. Eng. J., on the wire. 183 (2012) 492-503.

b [4] D. Quéré, “Fluid Coating on a Fiber.” Annu. Rev. hB Ca B 1  B   b b  b Fluid Mech. 31 (1999) 347-384. hT  hB CaT  Ca B 1  CaT / Ca B Developing Real-Time Control for Electrospinning of Nanofibers: Evaporation and Measurement Considerations for Aqueous and Non-Aqueous Solutions

Yunshen Cai, Thierry Desire, Xuri Yan, and Michael Gevelber Boston University, Department of Mechanical Engineering, Boston, Massachusetts [email protected]

Our research focuses on understanding the relationship between operating conditions and the resulting fiber diameter distribution as well as developing the knowledge base needed to design an electrospinning control system in order to achieve a consistent and repeatable process. In particular, we have been examining the role of solvent evaporation in fiber spinning process. For aqueous PEO solutions, the relative humidity is found to significantly affect fiber diameters and formation. While relative humidity has been reported to have an affect for non- aqueous solutions, the primary effect in terms of resulting fiber diameter is related to solvent evaporation rates.

Instrumentation has been developed (fig 1) to determine correlations between measurable variables such as straight jet diameter, bending angle, taylor cone volume and fiber current to the resulting fiber diameter. The objective is to develop the basis for implementing a measurement based control system to maintain the desired fiber diameter. This system is also useful in determining appropriate operating conditions (voltage and flow rate) to achieve desired fiber diameter (fig 2).

Figure 2: Operating regime of aqueous PEO solutions

AQUEOUS SOLUTIONS Our primary experiments for aqueous solutions have been with PEO [1, 2]. Fig 3 shows how fiber diameter varies as a function of volumetric charge density (I/Q), which reveals that these relations vary significantly with humidity rate. To a lessor degree, the slope of the correlation is also affected by pump flow rate. Since humidity affects evaporation rate (fig 4), we are investigating whether this can be theoretically shown to explain the change in diameter.

Figure 1: Measurement schematic To design a control system, we seek a measurable variable that correlates well to the ultimate fiber diameter. Both upper jet diameter and bending angle have been shown to correlate well [2], when combined with the relative humidity (fig 5).

The experimental study shown in fig. 5 are being repeated, but using an experimental apparatus that controls the relative humidity in a different fashion (ie using salt baths and humidifiers instead of controlled dry nitrogen flows, to insure there was no impact on the electrostatic conditions).

NON-AQUEOUS SOLUTIONS We have extended our experiments to consider non- aqueous solutions, with PVP to further investigate the role of evaporation. While relative humidity has also been shown to impact the electrospinning, the dominant impact is in terms of the solvent’s evaporation rate. Fig 4 shows Figure 3: Relation of charge density to fiber diameter for that for the solvents we are examining, the evaporation 7% PEO in water rate is nearly an order of magnitude greater than the aqueous solution, but that the charge density is significantly lower. Fig 6 shows the relation to measured upper jet diameter, which we will combine with evaporation rate to investigate whether a similar phenomenological relation as in fig 5 correlates with fiber diameter.

Figure 4: Evaporation rates for PEO/water and PVP/non- I/Q aqueous solvents Figure 6: Relation of upper jet diameter to charge density

ACKNOWLEDGEMENT We appreciate the funding support from the NSF (CMMI 0826106) and Army (W911QY-11-1-0014), and the contributions of David Ouk and Vicki Liu.

REFERENCES [1] X. Yan, M. Gevelber, “Investigation of Electrospun Fiber Diameter Distribution and Process Dynamics,” published in the Journal of Electrostatics, 68 (October 2010), pp. 458-264. [2] X. Yan, “Electrospinning of nanofibers: analysis of diameter distribution and process dynamics for control,” Figure 5: Relation of jet diameter and relative humidity to Thesis (Ph. D.)--Boston University, 2011. fiber diameter for PEO in water

Electro-Centrifugal Nanofiber Spinning

Tao Huang1, Jack Armantrout2, Kevin Allred3, and Thomas Daly3 1DuPont Central Research and Development, Experimental Station, Wilmington, DE 2DuPont Protection Technologies, Richmond, VA; 3DuPont Engineering, Wilmington, DE tao.huang@usa..com

ABSTRACT DuPont has developed an electro-centrifugal nanofiber spinning process and nanoweb technology to make nanofibers and nanowebs at high production rates. There are four key process parameters: spin disk diameter, rotation speed, electrostatic charging voltage and polymer feed rate.

INTRODUCTION Using DuPont’s new electro-centifugal nanofiber spinning process, nanofibers can be made and collected into a fibrous web that is useful as a selective barrier in applications such as: air and liquid filtration; flame retardancy; battery and capacitor separators; biofuel membranes; cosmetic facial masks; sensing applications; electronic/optical textiles; EMI shielding; chem/bio protective coatings; and biomedical applications, such as, hemostasis, wound dressings and healing, vascular grafts, tissue scaffolds, and a synthetic extra cellular matrix FIGURE 1. The high-speed video image of threads forming at a 9” high (ECM). speed rotating edge in electro-centrifugal spun nanofiber spin pack

In the electro-centrifugal nanofiber process, a polymer RESULTS AND DISCUSSION solution is deposited onto a high speed rotating disk, Figure 2 shows SEM images of nanofibers obtained from causing it to form a thin film on the disk surface. Strong a 10 wt% PEO/H2O solution directed onto a 6” diameter shear-thinning orients the entangled polymer chains rotating disk at a flow rate of 25 cc/min, rotation speed of within the thin film, and the Coriolis force induces thin 21 krpm, and direct charge of 73 kV. Figure 4 shows film banding, fingering instability and “shock wave” SEM images of nanofibers obtained from a 10 wt% instability. These thin film instabilities contribute to thin PEO/H2O solution directed onto a 9” diameter rotating film fibrillation, and the threads from the thin film disk at a flow rate of 60 cc/min, rotation speed of 21 fibrillation are stretched into nanofibers by the strong krpm, and direct charge of 72 kV. centrifugal force [1]. A high voltage electrostatic power supply is directly connected to the disk to charge the fibers and facilitate nanofiber and nanoweb formation.

DuPont’s centrifugal nanofiber spinning process provides a number of critical process advantages, including higher productivity due to the higher flow rate. It also provides a lower processing cost due to the commercial availability of production equipment and precision process control systems. It strives to provide new areas of impact and FIGURE 2. SEM images of nanofibers from a 10 wt% PEO/H2O provide fundamental capability outside the realm of other solution. Disk=6“ diameter; Flow rate=25 cc/min; Rotation speed=21 nanofiber technologies. krpm; Direct charge=72 kV.

EXPERIMENTAL With increased rotation speed or decreased flow rate, the Figure 1 shows the threads forming at a 9” high speed nanofiber size can be reduced significantly. rotating edge in electro-centrifugal spun nanofiber spin pack.

CONCLUSIONS In this study, we have demonstrated a high throughput electro-centrifugal nanofiber spinning process. The nanofiber size distribution and nanoweb formation have been studied versus polymer properties and process parameters.

REFERENCES FIGURE 3. SEM images of nanofibers from a 10 wt% PEO/H2O Tao Huang, From Centrifugal Spraying to Nanofiber solution. Disk = 9” diameter; Flow rate=60 cc/min; Rotation speed=21 Spinning, New Frontiers in Fiber Materials Science, krpm; Direct charge=72 kV. October 11–13, 2011, Charleston, South Carolina, The

Fiber Society.

Governing Equations for the Well-Enhanced Electro-Centrifuge Spinning Process

Afsaneh Valipouri1, Seyed Abdolkarim Hosseini Ravandi1, Ahmadreza Pishevar2 1Department of Textile Engineering, Isfahan University of Technology, 84156, Isfahan, Iran 2Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran [email protected]

STATEMENT OF PURPOSE APPROACH Electrocentrifugal spinning is a powerful technique for Materials: Poly (acrylonitrile) with Mn = 70000 g/mol spinning nanofibers, but this approach has been limited by and Mw = 100000 g/mol was obtained from Iran a stream of rotating air surrounding the nozzle. Exposing Polyacryle Co. N, N- dimethyl formamide (DMF) from the ejected liquid jet to the high velocity airflow causes Merck was used as the solvent of PAN. PAN powder was the jet to lose its solvent rapidly and as a consequence, the dissolved in DMF into solution with 13 wt% extension of the jet becomes more difficult, resulting in concentration at ambient temperature and was gently thicker nanofibers. To remove this air effect, in this study, stirred for about 24 h to prepare a homogenous solution an enhanced approach, named "air-sealed-centrifuge- for electrospinning. This concentration was found to be electrospinning system (ASCES)" is introduced, aiming at optimal concentration. minimizing also the diameter and variability of Air-sealed centrifuge electrospinning (ASCES): As can nanofibers. In addition, we propose a set of governing be seen in figure 1, the ASCES setup consists of a rotating equations for the dynamic of a polymer jet through drive shaft (A), an insulated plate(B), a rotating ASCES. cylindrical receptacle (C), a metallic cylindrical collector (D), a transparent door (E) and a high-voltage power INTRODUCTION supply (F). The rotating cylindrical receptacle holds a Nanofibers are an exciting new class of material used for syringe containing polymer solution. Polymer solution is several value added applications such as medical, ejected from the needle tip. Positive electrode from high- filtration, barrier, wipes, personal care, composite, voltage power supply is connected to the nozzle and the garments, insulation, and energy storage [1]. Generally, surrounding cylindrical collector is attached to the polymeric nanofibers are produced by electrospinning opposite polarity. The movable transparent door is used to process. A challenge associated with electrospinning is its prevent air from entering and exiting. production rate, as compared to conventional fiber spinning. The relatively low production rate of a traditional electrospinning has limited its industrial applications [2]. In recent years, an attempt has been made to enhance the production rate of nanofibers with the development of electro-mechanical system. Some researchers have combined centrifugal forces from a rotating disk with electrostatic forces to fabricate nano- scale fibers [3, 4]. The previous research has indicated that applying the centrifugal force may result in a significant increase in the production rate of nanofibers [5, 6]. Therefore, it is expected that this hybrid process be capable of a substantially higher production rate, as compared to conventional electrospinning method. Figure 1. (a) Schematic of air-sealed centrifuge Electro-centrifuge spinning, as a novel innovation, has electrospinning system, (A) rotating drive shaft (B) been limited by a stream of rotating air surrounding the insulated plate (C) rotating cylindrical receptacle (D) nozzle. Exposing the ejected liquid jet to the high velocity rotating metallic cylindrical collector (E) transparent door airflow results in thicker nanofibers [3]. (F) high-voltage power supply The first aim of this work is modifying electro-centrifuge spinning to remove airstream effect on nanofiber RESULTS AND DISCUSSION morphology. In addition, a general set of conservation Effect of elimination of air drag: As mentioned above, equations for mass, charge, and momentum is proposed as ASCES has been sealed from ambient air. Therefore, the a framework for polymer jet dynamic studies. It is worth inside trapped air has a rigid body rotation. Hence, no mentioning that no theoretical study has been yet reported significant collision occurs between polymer jet and air on formation of the jet through electro-centrifugal particles and evaporation rate decreases siginificantly. As spinning. a result, the jet has more time to propagate and elongate before solidification resulting in thinner fibers as comparision with electro-centrifugal spinning system. Figure 2 shows typical FESEM images of nanofibers fabricated by electro-centrifugal spinning and ASCES. (8) These samples were produced at rotation speed of 4320 (9) rpm and voltage of 15 kV. The mean diameter of where σ is the stress tensor and γ is the surface tension. nanofibers (± standard deviation) fabricated by electro- For flows in quasistatic electric fields, the stress tensor σ centrifugal spinning and ASCES is 291(± 53) and 134 (± consists of mechanical and electrostatic Maxwell stress 20) nm, respectively. It shows that air isolation of ASCES tensors. The electric conditions at the interface are has a significant effect on nanofiber morphology. (10) (11) where E0 is the electric field in the free space and qs is the surface charge density, which must satisfy the conservation of charge at the interface

(12)

where Ks is surface current density. Figure 2. Typical FESEM images of nanofibers fabricated by electro-centrifugal spinning (left) and ASCES (right) CONCLUSION In this study, a novel technique for producing ultrafine Governing equations: In ASCES, the liquid jet and high quality nanofibers has been developed by using originates from the rotating nozzle and flows towards the centrifugal and electrostatic forces simultaneously. The collector under centrifugal, Coriolis and electrical forces, fabrication process was skillfully sealed from ambient while air drag was eliminated from ASCES. The airflow. Using air-sealed spinning technique can enhance morphology of nanofibers strongly depends on the the quality and fineness of nanofibers. In addition, we features of the jet between the nozzle and the collector. proposed a set of conservation equations for mass, charge, The coordinate system used was an extension to and momentum as a framework for jet dynamic studies. cylindrical polar coordinates, (s,n,φ) where, s is the These equations are intended to serve as a basis for arclength along the jet and (n,φ) are polar coordinates in development of numerical simulation. any cross section of the jet. The fluid velocity is assumed to be uniform across the jet FUTURE WORK cross section, and the leaky-dielectric model is adopted to The goal of the future work is development of a numerical account for the effects of finite electrical relaxation time approach for prediction of jet dynamic in ASCES. In as well as nonzero tangential electric stresses at the jet addition, we will evaluate the performance of the surface. The model equations follow from the Navier– numerical model. Stokes equations, namely (1) REFERENCES [1] Z. M. Huang, Y. Z. Zhang, M. Kotaki, and S. (2) Ramakrishna, "A review on polymer nanofibers by electrospinning and their applications in nanocomposites," Composites Science and Technology, vol. 63, pp. 2223–2253, (3) 2003. (4) [2] C. J. Luo, S. D. Stoyanov, E. Stride, E. Pelan, and M. Edirisinghe, "Electrospinning versus fibre production methods: (5) from specifics to technological convergence," Chem. Soc. Rev., vol. 41, pp. 4708-4735, 2012. And the conservation law of charge, [3] F. Dabirian, S. A. H. Ravandi, and A. R. Pishevar, (6) "Investigation of Parameters Affecting PAN Nanofiber Production Using Electrical and Centrifugal Forces as a Novel Where v: fluid velocity, ρ: fluid density, p: pressure, fe: electrical force, f : centrifugal force, f : Coriolis force, σ: Method " Current Nanoscience, vol. 6, pp. 545-552, 2010. c C [4] C. T. Peterson, "Hybrid Nanomanufacturing Process free charge density, E: electric field, ε: permittivity of the for High-Rate Polymer Nanofiber Production," Degree of jet, ε0: permittivity of the free space, ω: angular velocity, Master of Science University of Nebraska - Lincoln, 2010. r: position vector in the rotating frame, i: electrical [5] M. R. Badrossamay, H. A. McIlwee, J. A. Goss, and current carried by the jet, and K: electrical conductivity of K. K. Parker, "Nanofiber Assembly by Rotary Jet-Spinning," the jet. Nano Letters vol. 10, pp. 2257–2261, 2010. Conditions at the interface between the liquid and air: [6] K. Sarkar, C. Gomez, S. Zambrano, M. Ramirez, E. de The geometry of the free surface of the jet can always be Hoyos, H. Vasquez, and K. Lozano, "Electrospinning to TM given in implicit form as F(n,s,߮,t)=0. We denote the forcespinning ," Materials Today, vol. 13, pp. 12-14, 2010. normal and the tangent vectors to the jet free surface by n and t. The evolution of the interface is governed by the kinematic condition (7)

Nanofibers

A Historical Perspective on Nanofibers: Can We Make It More Relevant?

H. Young Chung Et Esus [email protected]

INTRODUCTION MAN MADE NANOFIBERS: A BRIEF HISTORY Since the publication of Prof. Darrell Reneker’s seminal Scientists and engineers have continually investigated papers on electrospinning, electrospinning of nanofibers ways of making fiber diameter smaller. Many of initial has been a subject of numerous publications. The impetus came from military needs during WWII. We will simplicity of laboratory electrospinning equipment has briefly look at their origins and commercialization effort. helped many starting young professors to get into the research on electrospinning. Many of early papers focused AVAILABLE TRUE NANOFIBERS on the novelty of producing sub-micron scale fibers under While electrospinning is a simple method of producing various processing conditions. More established nanofiber, it is not the only methods. We will survey both laboratories have published papers on different natural and synthetic methods from cellulosics to collagen applications, alignment of nanofibers, core-shell structure, and to inorganic in nature. Their pluses and minuses will hollow nanofibers, sol-gel process and inorganic be discussed. Some thoughts will be given on why nanofibers and new equipment as well as surface commercialization of electrospun nanofibers beyond characteristics. filtration have not progressed as initially envisioned.

Early presentations by this author focused on the WHAT MAKES ELECTROSPUN NANOFIBERS industrial aspects of electrospinning and successful INTERESTING UNTIL NOW commercialization of electrospun nanofibers on filtration There have been two major impetuses on widespread applications. These papers were carefully vetted by interests in electrospinning; academic and industrial. Donaldson Company, the author’s employer until his Academically, two factors are important; the enthusiastic retirement. In those papers, the author has pointed out curiosity of Prof. Reneker and his colleagues in polymer potential pitfalls of misapplications of nanofibers. He has science and simplicity and desire of producing nanofibers repeatedly pointed out that it was not just the fiber size, in the fiber science. Later on, scientists from other but also surface characteristics and spaces-in-between disciplines make the electrospinning exciting. nanofibers that that determines success and failures of commercial applications. Commercially, again there have been two major impetuses; the success of Donaldson company in Since retirement from an industrial environment, the enhancing the performances of its filtration products via author has expanded his view on various nanofibers and electrospun nanofibers and fiber/polymer industries to examined the ways of helping research and development widen their product portfolio. Again, other companies and of nanofiber more relevant than ever. This is the focus of institutions made the whole picture interesting. this presentation. WHAT MAKES ELECTROSPUN NANOFIBERS TRAGEDY OF ASBESTOS: NATURAL WONDER INTERESTING: THE FUTURE NANOFIBER The author intends to discuss some of areas that interest It is often said that one who forgets the past is prone to me beyond what has been discussed so far. Many repeat the mistakes. Since the products containing industrial researchers have focus on business at hand, asbestos is no longer available commercially, asbestos such as developing new products in related area and fibers are rarely mentioned these days. However, for a improving performances, productivity and reducing costs. very long time, asbestos fibers enjoyed successful This often happens at the expense of intellectual curiosity application in many areas. It would be beneficial to and it certainly has been the case of the author to some briefly review why this fiber was extensively used. I will extent. I will present some areas that have not been fully briefly review properties and applications, such as explored yet, such as morphology and charging insulation, filtration and chlor-alkaline application. phenomena with limited data.

Electrospun Nanofibers Functionalized with Cyclodextrins and Their Potential Applications

Asli Celebioglu, Fatma Kayaci, Zeynep Aytac, Yelda Ertas, and Tamer Uyar UNAM-Institute of Materials Science & Nanotechnology, Bilkent University, Ankara, 06800, Turkey [email protected]

OBJECTIVE Our research mostly focuses on the electrospinning of functional polymeric nanofibers incorporating cyclodextrins (CD) and cyclodextrin inclusion complexes (CD-IC). Moreover, electrospinning of polymer-free CD and CD-IC nanofibers without using a carrier polymer matrix are also being performed successfully by our research group. The electrospun nanofibers functionalized with CD and CD-IC have potential applications in filtration, textile, food packaging, biotechnology as well as other advanced systems.

INTRODUCTION a. Cyclodextrins (CD) are cyclic oligosaccharides consisting of α-(1,4)-linked glucopyranose units. guest host The native CDs are named as α-CD, β-CD and γ- CD having 6, 7 and 8 glucopyranose units, respectively (Figure 1a), in addition, chemically modified CDs such as methyl-CD and hydroxypropyl-CD are also widely used due to their higher solubility and non-toxicity. CD molecules Cyclodextrin inclusion complex (CD-IC) have truncated cone-shaped molecular structure and the CD cavity has relatively hydrophobic nature b. and due to the unique properties of CD, they form Figure 1. (a) Chemical structure and approximate non-covalent host-guest inclusion complexes (IC) dimensions of α-CD, β-CD and γ-CD, (b) CD-IC. (Figure 1b) with variety of molecules such as antibacterials, drugs, , flavors, essential APPROACH oils, textile additives and pollutants, etc. By In our studies, we produce electrospun polymeric forming CD-IC, the shelf-life of the volatile nanofibers incorporating CD and CD-IC of several textile/food additives can be increased and types of additives such as antibacterials, controlling the release of poorly soluble drugs can antioxidants, flavors, essential oils, drugs, etc. In be achieved and toxic organic waste can be addition, we successfully electrospun CD and CD- removed from the environment, etc. Hence, CD and IC nanofibers without using a carrier polymer CD-IC are quite applicable in many areas such as matrix. pharmaceuticals, functional foods, filters, cosmetics, textiles, etc. RESULTS AND DISCUSSION CD are very effective for the stabilization of Electrospinning is a facile and very cost-effective volatile additives such as antibacterials, technique for producing nanofibers from a variety fragrances/flavors, essential oils, antioxidants and of materials such as polymers, polymer blends, sol– drugs by complexation and they provide slow gels, composites, etc. In addition, incorporation of release or controlled release as well as high functional additives and nanoparticles, etc in the temperature stability. Here, we prepared CD-IC of electrospun nanofibers can be achieved due to the certain additives such as antibacterial (triclosan), design flexibility of the electrospinning process. fragrance/flavor (vanillin), essential oil (eugenol) Due to the very high surface area and nanoporous and (vitamin E). Then, these CD-ICs structure along with specific functionality, were blended with certain polymeric matrix and electrospun nanofibers and their mats are extremely then electrospun into functional applicable in biotechnology, membranes/filters, nanofibers/nanowebs (Figure 2) [1-3]. With this textiles, sensors, electronics, energy, approach, functional nanotextile materials and/or environmental, etc. food packaging materials can be obtained having long-lasting functionality due to stabilization and sustained/controlled release of these additives by CD complexation. In addition, we produced CD-IC with certain drugs and we incorporated these CD- ICs in biocompatible/biodegradable polymeric nanofibers by electrospinning. The stabilization and controlled/sustained release of drug molecules from the electrospun nanoweb were studied. These drug- CD-ICs functionalized nanofibers/nanowebs would be extremely appealing in drug delivery systems, wound dressing and tissue engineering areas due to the exclusive properties obtained by combining the very large surface area of nanofibers with specific functionality of the CDs.

Figure 3. SEM images of HPβCD, HPγCD and MβCD nanofibers electrospun from water, DMF and DMAc.

CONCLUSION We electrospun nanofibers functionalized with CD and CD-IC and investigate their potential applications in filtration, textile, food packaging, biotechnology. The electrospun CD nanofibers have unique properties due to their very high surface area along with specific functionality of the CD.

KEYWORDS Figure 2. Schematic representations of the (a) formation cyclodextrin; electrospinning; nanofiber of the vanillin/CD-IC, (b) electrospinning of the PVA/vanillin/CD-IC nanofibers. ACKNOWLEDGMENTS Dr. T. Uyar acknowledges TUBITAK (project # In another study, we successfully performed the 111M459 and 110M612) and EU FP7-PEOPLE-2009- electrospinning of CD and CD-IC nanofibers RG Marie Curie-IRG (project # PIRG06-GA-2009- without using a carrier polymer matrix. The 256428) for funding. State Planning Organization (DPT) electrospinning of nanofibers from non-polymeric of Turkey is acknowledged for the support of UNAM- systems such as CD is quite challenging. CD Institute of Materials Science & Nanotechnology. F. molecules are capable of self-assembly and form Kayaci and A. Celebioglu acknowledge TUBITAK- aggregates via intermolecular hydrogen bonding in BIDEB for the national graduate study scholarship. their concentrated solutions and such aggregates present in the CD solutions can be effective for the REFERENCES 1. F. Kayaci and T. Uyar, “Solid Inclusion Complexes electrospinning of CDs into nanofibers. For the first of Vanillin with Cyclodextrins: Their Formation, time we showed that electrospinning of CD Characterization, and High-Temperature Stability” nanofibers by itself without the use of a carrier Journal of Agricultural and Food Chemistry, 59 polymer matrix is possible. We have investigated (21),11772–11778, 2011. the electrospinning of nanofibers from three 2. F. Kayaci and T. Uyar, “Electrospinning of zein different chemically modified CD (HPβCD, nanofibers incorporating cyclodextrins” Carbohydrate HPγCD and MβCD) in three different solvent Polymers, 133, 641-649, 2012. systems (water, DMF and DMAc) without using 3. F. Kayaci and T. Uyar, “Encapsulation of any carrier polymer matrix (Figure 3) [4-5]. We vanillin/cyclodextrin inclusion complex in electrospun polyvinyl alcohol (PVA) nanowebs: Prolonged shelf-life observed that the morphology and the diameter of and high temperature stability of vanillin” Food the resulting electrospun fibers significantly vary Chemistry, 133 (3), 641-649, 2012. with the type of CDs as well as the type of solvent 4. A. Celebioglu and T. Uyar, “Cyclodextrin systems used. In a different study, the Nanofibers by Electrospinning” Chemical electrospinning of polymer-free nanofibers from Communications, 46(37), 6903-6905, 2010 (COVER). inclusion complexes of HPβCD with triclosan 5. A. Celebioglu and T. Uyar* “Electrospinning of (HPβCD/triclosan-IC) was achieved successfully Nanofibers from Non-Polymeric Systems: Polymer-free [6]. The antibacterial tests indicated that the Nanofibers from Cyclodextrin Derivatives” Nanoscale, 4, HPβCD/triclosan-IC nanofibers were very effective 621-631, 2012. 6. A. Celebioglu and T. Uyar, “Electrospinning of against E.coli and S.aureus. Polymer-free Nanofibers from Cyclodextrin Inclusion Complexes” Langmuir, 27, 6218-6226, 2012.

Spinning Functional PLA Nanofibers for Controlled Release, Protein Capture, and Sensing

Margaret W. Frey1, Dapeng Li1,2, Chunhui Xiang1,3, Ebru Buyuktanir4,5 1Department of Fiber Science & Apparel Design, Cornell University; 2Bioengineering, University of Massachusetts at Dartmouth; 3Apparel, Events and Hospitality Management, Iowa State University; 4Liquid Crystal Institute, Kent State University; 5Chemistry, Stark State University [email protected]

INTRODUCTION intended functionality to the resulting fibers and Starting from a base Polylactic acid nanofiber (PLA) fabrics. our research team has developed nonwoven fabrics with a wide variety of capabilities. The RESULTS AND DISCUSSION hydrophobic, biocompatible and biodegradable For nanofiber production, PLA has many desirable properties of PLA have been modified by adding properties. First and foremost, PLA can be hydrophilic, active and functional materials to the electrospun into nanofibers from several solvents to spinning solution and producing nanofibers via form consistent, uniform fibers with predictable electrospinning. Addition of cellulose nanocrystals diameters (Figure 1). As a biocompatible, and pesticides created fibers capable of steady biodegradable, renewable resource polymer, PLA is pesticide release over a 16 week period with the also an excellent target material for a variety of release rate governed by the cellulose content. biomedical and environmental uses. PLA alone Addition of biotin to the spinning dope resulted in a however has some limitations. PLA is hydrophobic, non-woven fabric capable of rapid and efficient a drawback in aqueous biological systems. PLA streptavidin protein capture. When liquid crystal also has limited functionality for interacting with molecules were added to the spinning solution, the biological systems. As with most polymers, PLA resulting fibers had a liquid crystalline core capable does not crystallize significantly in the of responding to electrical and thermal stimuli. The electrospinning process, limiting the strength of the wide functional materials created via this simple resulting fibers and fabrics. strategy have found uses in systems ranging from PLA biodegradability could provide an green houses to microfluidic devices. advantage for controlled release pesticide or herbicide delivery. By using a controlled release APPROACH delivery system, farmers could avoid runoff, PLA nanofibers have been electrospun at room 30 temperature from solution in a chloroform/acetone CB+PLA/0% Cellulose 2 CB+PLA/1% Cellulose R = 0.9962 mixed solvent or at elevated temperature from 25 dimethyl formamide (DMF). Cellulose nanocrystals CB+PLA/10% Cellulose were suspended in the electrospinning dope. Biotin 20 was either suspended or dissolved in the 15 electrospinning R2 = 0.9756 dope. A small 10 Cumulative Release % Cumulative

molecule liquid 2 R = 0.9998 crystal (5CB) 5 was dissolved 0 in the 0 2 4 6 8 1012141618 electrospinning Time (weeks) dope. Resulting Figure 2: Addition of cellulose nanocrystals to PLA increased fibers were hydrophilicity and model pesticide release rate characterized to Figure 1: PLA nanofibers determine the degradation or the need for repeated application of distribution of pesticides. To make the PLA more compatible with the additive ingredient within the nanofibers and to agricultural chemicals and environments, we sought confirm that the additive ingredients provided the to improve hydrophilicity by incorporating a hydrophilic material which is also biodegradable and rapidly renewable. Cellulose nanocrystals added at properties. A nematic to isotropic thermal transition loadings up to 10% w/w PLA increased the was observed via polarized light microscopy and hydrophlicity of the nanofibers and also increased differential scanning calorimetry (DSC) at the the release rate of model agricultural chemicals from expected temperature. Rapid and repeatable the nanofiber fabrics (Figure 2). Green house trials switching in an electrical field was also confirmed that the recommended does of pesticide demonstrated. The liquid crystal could be loaded could be delivered to a pole bean plant from a 2mm into the PLA x 2mm piece of electrospun fabric. Addition of nanofibers at cellulose nanocrystals also increased both PLA proportions greater crystallinity within the fibers and the rate of PLA than 50% of the biodegradation.1,2 overall fiber. X- Although PLA is biocompatible, specific ray diffraction and binding of biological molecules to PLA does not DSC occur readily. To create binding sites for characterization streptavidin protein, a common link in biosensor also confirmed that Figure 3: PLA/5CB nanofibers assays, we added biotin to the PLA fibers. Biotin the addition of the exhibit birefringence under crossed was added via suspension in small molecule polars. The first order red plate PLA/Chloroform/Acetone solutions or co-dissolved retardation confirms alignment of the liquid crystal liquid crystal with the fiber axis. in PLA/DMF solutions. When biotin was suspended increased in PLA solution, the resulting fibers contained a very crystallization of non-uniform distribution of biotin agglomerates and the PLA during the electrospinning process.7 crystals. Additionally, the yield of biotin in the fibers was significantly lower than predicted from CONCLUSIONS the original solutions. When biotin was co- Using one easily spinnable fiber and taking dissolved with PLA, the distribution of biotin in the advantage of the tolerance of the electrospinning resulting fibers was uniform. No agglomerates or process to large loadings of additives, we have crystals were observed and biotin was found to be produced fibers with a broad range of functionality. enriched at the Uniform morphologies and submicron diameters outer fiber were maintained even at high additive loadings up to surface 18 wt% biotin, 10 wt% cellulose nanocrystals, 50 compared to wt% Columbia Blue as a model pesticide and 70 predictions wt% 5CB liquid crystal. In all cases, the target based on functionality from the additive material was uniform achieved in the final fibers. distribution throughout the KEYWORDS: Electrospinning, Poly Lactic Acid, fiber. Functional Nanofibers Figure 3: Addition of streptavidin to a Successful HABA dye solution turns the solution from binding of ACKNOWLEDGMENT yellow to orange. After addition of biotin streptavidin to The authors acknowledge the support of the National containing PLA nanofibers streptavidin binds with biotin and is removed from the fibers Textile Center, The National Science Foundation solution and the color shifts back to yellow. occurred Grant DMR-1120296 and LCI. rapidly (Figure 3).3-6 REFERENCES Evidence of phase separation during the (1)Xiang, C. et al., J. Appl. Pol. Sci. 2012, in press. electrospinning process was further confirmed when (2)Xiang, C. et al., J. Bio Mat. & Bioenergy 2009, 3, a small molecule liquid crystal was co-dissolved 147. with PLA. Resulting fibers had a distinct core-shell (3)Frey, M. W et al. , J. Bio Mat. & Bioenergy morphology with a PLA shell and liquid crystalline 2007, 1, 220. core. The highly birefringent core of the fibers was (4)Li, D et al. , Polymer 2007, 48, 6340. easily visible in polarized light microscopy (Figure (5)Li, D. P.; et al. , J. Mem. Sci. 2006, 279, 354. 4) and evidence of liquid crystal orientation along (6)Li, D. P.; et al. , J. Mem. Sci. 2006, 286, 104. the nanofiber length was found. Within the (7)Buyuktanir, E. A.; et al. , Polymer 2010, 51, nanofiber, the liquid crystal maintained responsive 4823. Melt Spinning PP: A Formation Model Development of “Hard Elastic” Behavior

Dr. Michael Jaffe New Jersey Institute of Technology, Newark, New Jersey, USA [email protected]

Control of polymer phase structure and these materials is incomplete. We propose a morphology can give rise to fibers with model to relate polymer backbone unusual transport behavior. One example of chemistry, molecular weight distribution and this is deformed and heat set “hard elastic” melt processing variables to hard elastic polypropylene, leading to microporous behavior and ultimately to the formation of structures. fibers with controlled microporosity. The results of the model suggest that it is a Highly oriented, highly crystalline polymer combination of MWD and crystallization films showing high elastic recovery and environment that leads to the integration of allowing for the formation of a stable crystalline morphology and chain topology microporous morphology after straining and required for hard elastic/microporous heat-setting have been known since the performance. 1960’s yet mechanistic understanding of

Characterization of Compressive Properties of Electrospun Mats

Looh Tchuin (Simon) Choong and Gregory C. Rutledge Department of Chemical Engineering, Massachusetts Institute of Technology [email protected]

STATEMENT OF PURPOSE An unconfined uniaxial compression test was carried out In this work, we characterize the compressive response of using the Agilent T150 UTM with a load cell of 500mN. electrospun mats with sub-micron fibers using an existing Three 1mm diameter discs were cut out from the heat- model that has been applied to micron size fibers like treated PSU mat. Each of the discs was subjected to three textiles and paper pulps. compression cycles, each of which unloads when a force of 400mN is reached. The compression was carried out at INTRODUCTION a strain rate of 0.005s-1. The applied load (F) on the The high porosity (or low solidity) of electrospun mats is specimen and the corresponding thickness change (Δt) of a desirable characteristic for filtration applications, the specimen were recorded. usually resulting in lower pressure drop across the filter [1]. However, because filtration processes are usually The planar surface area (A), initial thickness (t0) and pressure-driven, some compression of the filter mat is solidity (s0) of mat were used to convert the raw data possible, resulting in a reduction of the porosity of from the UTM into stress (PF/A), strain (Δt/t0) and electrospun mat. Therefore, it is beneficial to study the solidity. compressive response of electrospun mats under pressure. (2) Van Wyk [2] provided the first mechanistic explanation for the compression behavior of fibrous porous media, assuming the mechanism of beam bending between Equation 1 was fitted to the post-processed data using contact points. A power relationship between stress (P MATLAB and the corresponding kE and n values were and solidity (s) was developed based on the non-linear obtained. The hysteresis and the percent change of increase in the number of fiber contact points arising from solidity for each compression cycle were also calculated. compression. RESULTS AND DISCUSSION The fiber diameter of the electrospun PSU was , (1) (0.7±0.2)μm. Typical stress-strain curves for the three where is a constant that accounts for the effect of the compression cycles are shown in Figure 1. The first non-uniformity of forces at the contact points and compression cycle resulted in the greatest irrecoverable morphological aspects of the fibers, is the Young’s strain (~0.6). This is likely due to the majority of the fiber modulus of the fiber, and is the power exponent, which slippage that occurs during the first loading segment [1]. depends on the nature of the fiber network. Since there is no fiber slippage during the unloading segments, all three cycles have almost identical unloading curve to each other. The irreversible fiber slippage causes In Van Wyk’s case, n is equal to 3 for a randomly an increase in solidity of mat and that is the highest for oriented 3D network of fibers. Toll [3] further refined the the first cycle (+61%) and remains nearly constant Van Wyk model and concluded that n is equal to 5 for a (+10%) for the subsequent cycles. The starting solidity is planar network of fibers in which the fibers are randomly 0.075±0.04 and the final solidity is 0.21±0.02. orientated in the plane. Toll also suggested that the exponent for solidity could be higher if the fibers are aligned, and proposed Equation 1, which is a more general power law equation, applicable to the compression of any network of fibers.

APPROACH Bisphenol-A polysulfone (PSU) (Sigma Aldrich, Mw = 35,000 g/mol) was first dissolved in dimethylformamide (DMF) to form the polymeric solution and then electrospun to form a PSU fiber mat. The as-spun PSU mat was then heat treated at 210oC for 30 minutes for the ease of handling. The fiber diameter of the electrospun PSU was measured from scanning electron microscopy (SEM) images taken with a JEOL-JSM-6060.

Figure 1: Stress-strain response of the electrospun mat under three compression cycles. Similarly, the hysteresis is also the highest (40 kPa) for Table I: Summary of the fitted kE and n values from Equation 1, the the first cycle and about the same for the subsequent increase in solidity, and hysteresis after each compression cycle. cycles (~10kPa). Hysteresis, albeit small, still exists after a few cycles because of the non-recoverable energy dissipation from the viscoelasticity of the fibers and from the friction loss when fiber-fiber contacts are formed.

The compressive response of the PSU mats exhibits the power law relationship as predicted by the Toll model, as shown in Figure 2. The fitted kE and n values for all CONCLUSIONS compression cycles are recorded in Table I. Both kE and The stress-solidity relationship of electrospun PSU mats n during the loading segment increase with increasing follow the general power law expression proposed by cycle number. The n for the first loading segment is less Toll. The compressive response of electrospun PSU mat than 3, and is likely due to the presence of some loose is not completely elastic; this is attributed to friction fibers. As the number of cycles increases, the network of occurring at the contact points and the viscoelasticity of fibers more closely resembles that of a planar network. fibers. Most of the irreversible compression occurs during The n for all the unloading segments are ~5.9±0.7, which the first compression cycle due to fiber slippage, and is slightly higher than 5. That is likely due to some fiber decreases with each subsequent cycle. Further tests with alignment, which is induced by fiber slippage during higher number of compression cycles are currently loading. underway.

KEYWORDS Compression, electrospinning, fibers.

ACKNOWLEDGMENT I would like to thank Matthew Mannarino for the useful discussion and the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia, for funding the research reported in this paper through the Center for Clean Water and Clean Energy at MIT and KFUPM under PROJECT NUMBER R5-CW-08.

REFERENCES [1] Zhu S., Pelton R.H., Chemical Engineering Science, Figure 2: Equation 1 fitted into the unloading segment of the second 1995 vol. 50, No. 22, pp. 3357-3572. compression cycle of one of the three mats. [2] Van Wyk C.M., Journal of the Textile Institute Transactions, 1946 vol. 37 (12) pp. T285-T292. [3] Toll S., Polymer Engineering & Science, 2004 vol. 38 (8) pp. 1337-1350.

Fabrication of Composite Polyallylamine-Nanodiamond Fibers

Marjorie A. Kiechel, Ioannis Neitzel, Vadym N. Mochalin, Yury Gogotsi, Caroline L. Schauer Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, USA [email protected]; [email protected]

OBJECTIVE NDs (as-received UD90, oxidized [9] and milled The objective of this study is to improve the [10]) on and within the fiber strands was dispersion of nanodiamond (ND) particles by investigated. electrospinning aqueous solutions of polyallylamine (PAH) with differently processed APPROACH ND powders. Solution preparation. Solutions of aqueous PAH and 0.5 wt% aqueous ND dispersions were mixed INTRODUCTION in various volume ratios. Unless indicated, all Composites that are made up of polymers and ND aqueous solutions are prepared in doubly distilled [1-8] are attractive materials for many applications water. The pH of all the solutions were determined ranging from biocompatible scaffolds [4, 5] to using pH strips at 23-25°C and 15-20% relative transparent coatings [6]. NDs are known for their humidity (RH) and in triplicates. combination of superior diamond properties with a Fiber formation. The solution was electrospun large accessible surface area that may be covered using the parameters based on the method with various functional groups [8, 9]. It can further described by Schiffman et al [12]: applied voltage be incorporated into matrices, such as polymers, to of 10 kV, needle tip-to-collector distance of 10 cm, impart mechanical integrity or solution flow rate of 0.50 mL/hr, 21G needle functionality/specificity for a number of under- gauge, 23-25°C and 15-20% RH. All mats were explored applications that include biosensing, drug spun for 1 h, peeled off manually from the delivery, chromatographic sensors and tissue collector and stored in a desiccator prior to engineering. However, a major issue when characterization. incorporating NDs into polymers is the Fiber characterization. The surface morphology agglomeration of the nanoparticles [6] that often of the spun mats were imaged using a Zeiss Supra occurs, compromising material properties. 50VP FESEM after coating the sample with around Recently it was reported that salt assisted milling 5 nm thick Pt/Pd layer for 35 s at 40 mA. N=50 of ND could be used to obtain single dispersed ND fiber diameters were analyzed using ImageJ particles in aqueous solutions at high pH [10]. software (NIH). Transmission electron microscopy (TEM) was likewise performed to image the Fabrication of polymer fibers via electrospinning is nanodiamond particles inside the spun mats. a simple, flexible and controllable process that creates fiber mats with small diameters and RESULTS AND DISCUSSION consequently increased surface area-to-volume All blend ratios that were prepared could be ratio [11]. Numerous polymers such as electrospun into fiber mats. Of particular interest polyacrylamide (PAA) and polyamide 11 have was the sample containing the milled ND. Milling been previously electrospun with oxidized NDs for of the ND was previously reported as a uniform improved mechanical properties [6]. However, and shelf-stable dispersion of ND [10]. All three agglomeration of the NDs inside and on the surface ND types utilized have oxygen-functionalized of the fibers was observed. surfaces and show a negative zeta potential, where –COOH groups convert into COO- groups at high We were the first to report on the electrospinning pH, promoting small agglomerate size due to of neat PAH (free base, pH 11), a cationic polymer repulsive interactions. The aqueous solution pH in aqueous solutions [12]. This approach allows was adjusted to pH 11 and the solution was stored processing of ND colloidal solution at high pH. at ambient conditions to maintain uniform Also, the presence of free amine groups in PAH is dispersions [10]. The pH of all the test solutions expected to help uniformly disperse the carboxylic was measured to be pH 11, indicating that the NDs acid-functionalized NDs. Here, we report the are still under stable pH conditions preventing loading of NDs into aqueous PAH solutions prior reaggregation. to electrospinning. Distribution of three types of Figure 1 displays the representative FESEM images and mean fiber diameters of the 1:1 blend ratio of PAH-ND. The addition of NDs to the A detailed investigation of the mechanical and polymer matrix seems to increase the mean chemical properties of the designed fibrous diameters but all mean counts are still within the composite is currently underway. Moreover, standard deviations of each sample. Fibers were ongoing studies involve how loading and bead-free, cylindrical and with few branched or dispersion of NDs in an anionic (polyacrylic acid), junction points. neutral (polyethylene oxide) or cationic (PAH) polymer matrix affects material properties. All neat PAH, 150 ± 41 nm as received, 236 ± 89 nm these would allow a more in depth understanding of how addition and increased loading of ND may affect and potentially improve the composite fiber mats for potential applications as biosensors, filtration membranes, coatings, microfluidic 2 µm devices, tissue implants and drug delivery systems.

oxidized, 185 ± 08 nm milled, 206 ± 114 nm ACKNOWLEDGMENT The authors wish to thank: Dr. Edward Basgall of the DU Centralized Research Facilities (CRF) for assistance with the FESEM; Dr. Craig Johnson of CRF and Olha Mashtalir for helping with TEM imaging; Amanda Pentecost and David Freiberg for lab assistance. MSA would like to thank FIGURE 1. Representative FESEM images of electrospun PAH Philadelphia IFT and the DU Engineering Design [9], as-received ND-PAH, oxidized ND-PAH and milled ND- Fellowship. PAH in 1:1 blend ratios.

REFERENCES [1] Sirotinkin, N. V., Voznyakovskii, A. P., and Ershova, A. N., Physics of the Solid State, 46, 2004, 746-747. [2] Neitzel, I., Mochalin, V., and Gogotsi, Y. in Nanocrystalline Diamond (O. Shenderova, Ed.), CRC Taylor and Francis Group, 2012. [3] Neitzel, I., Mochalin, V., Knoke, I., et al., 10 nm NDs inside Composites Science and Technology, 71, 2011, fiber 710-716. [4] Zhang, Q. W., Mochalin, V. N., Neitzel, I., et al., Biomaterials, 33, 2012, 5067-5075. FIGURE 2. Representative TEM image of electrospun ND-PAH in 1:1 blend ratio. [5] Zhang, Q. W., Mochalin, V. N., Neitzel, I., et al., Biomaterials, 32, 2011, 87-94. Figure 2 displays a representative TEM image of [6] Behler, K. D., Stravato, A., Mochalin, V., et al., the NDs (~5 nm diameter for a single particle [9]) ACS Nano, 3, 2009, 363-369. inside a fiber strand. The images confirm that solid [7] Mochalin, V. N., Neitzel, I., Etzold, B. J. M., et PAH strands were able to disperse and prevent al., ACS Nano, 5, 2011, 7494-7502. reagglomeration of the NDs during [8] Mochalin, V. N., Shenderova, O., Ho, D., et al., electrospinning. Single ND particles can be clearly Nature Nanotechnology, 7, 2012, 11-23. seen in the polymer matrix. Moreover, no [9] Osswald, S., Yushin, G., Mochalin, V., et al., embrittlement or breakage of the fibers was Journal of the American Chemical Society, 128, observed, indicating strong interactions between 2006, 11635-11642. the PAH and carboxylic acid functionalized-NDs. [10] Pentecost, A., Gour, S., Mochalin, V., et al., ACS Applied Materials & Interfaces, 2, 2010, CONCLUSIONS AND FUTURE WORK 3289-3294. The addition of as-received, oxidized and milled [11] Subbiah, T., Bhat, G. S., Tock, R. W., et al., J. ND to aqueous PAH solutions yielded bead-free Appl. Polym. Sci., 96, 2005, 557-569. electrospun fiber mats loaded with well-dispersed [12] Schiffman, J. D., Austero, M. S., Donius, A. NDs inside the fiber strands. E., et al., Journal of Polymer Science Part A: Polymer Chemistry, Manuscript No. JPOL-A-12- 0833, 2012.

Sensors and Electrical Properties

Base Fiber Technologies for Smart Textiles

R. Hufenus1, D. Hegemann1, S. Gaan1, F.A. Reifler1, L.J. Scherer2 1Laboratory for Advanced Fibers, Empa, St. Gallen, Switzerland 2Laboratory for Protection and Physiology, Empa, St. Gallen, Switzerland [email protected]

INTRODUCTION two drying units and one UV-curing chamber. Coating Electrically conductive (e-) and optical (o-) textile fibers experiments were performed using withdrawal speeds in with good flexibility, robustness and haptics are essential the range of 1.5 to 8.8 m/min. for integration of electronics into textiles. The objective of this research is to develop textile core modules which As an alternative, overjacketing extrusion (i.e. wire enable the design and manufacturing of truly wearable coating technique transferred to polymeric filaments) was functional clothes. Recently we have developed a low- taken into consideration, where the monofilament passes pressure plasma sputtering process to deposit a 100-200 through the core of a crosshead extrusion die and is nm thin silver layer on common mono- or multifilaments coated with the polymer melt. After the coating process, [1]. To prevent corrosion and unwanted contacting of the the filament is cooled in air or water. The coating velocity conductive coatings, a proper insulation is necessary. (typical range for the current laboratory setup: 5 to 100 m/min) is determined by the action of the take-up unit Dip-coating is a simple and inexpensive method to situated after the cooling zone. deposit a liquid film on the surface of textile fibers. UV- curable polyurethane (PU) aqueous dispersions give high Using our pilot bicomponent melt-spinning plant [6], we performance thin flexible coatings which exhibit excellent produced POFs in a single-step process. As core material physical properties [2]. An interesting aspect about UV- a well-processable cyclo olefin polymer (COP) is used. curable coatings is that the uncured portions can be easily The fluorinated sheath polymer chosen provides the removed while the cured coatings have excellent washing desired fiber flexibility, and its comparatively low fastness, enabling selective inter-connects in textiles. refractive index maintains the light within the transparent Wire coating is widely used for the sheathing of electrical core. wires and cables [3]. The goal of our activities is to transfer this technique to polymeric filaments. RESULTS AND DISCUSSION Our low-pressure plasma sputtering process yields silver Polymer optical fibers (POF) have been implemented in coated fibers enabling the development of e-textiles that textiles for a wide range of applications in illumination behave and perform like conventional textiles in terms of and sensing [4]. However, most commercially available robustness, flexibility and haptics, but are capable to be POFs are based on poly(methyl methacrylate) (PMMA) used as interconnection platform for technology and possess diameters exceeding 200 µm to facilitate light empowered clothing (Figure 1). transmission. As a result, the respective fibers show insufficient bendability and handicap textile production and application. Using bicomponent melt-spinning technology we developed highly flexible prototype POFs that fulfill the requirements of textile processes.

EXPERIMENTAL For e-fibers, plasma-metallized polyamide 6.6 (PA 6.6) monofilament fibers (diameter: 78.5 μm) with a 200 nm silver layer were produced as starting point. The metallization was performed using an optimized magnetron sputtering process enabling the continuous and uniform coating of fibers [5]. Sputter-deposited Ag layers show a dense morphology yielding a resistivity of <10 Ω/cm on the PA 6.6 monofilament fibers. Figure 1: Plasma silver coated multifilament with To achieve an insulating layer, coating solutions were maintained textile properties. prepared using a UV-curable PU dispersion, carboxymethylcellulose (CMC, high viscosity rheological Thin insulating coatings have successfully been applied to agent) and photoinitiators. Dip-coating was done on a conductive plasma-metallized monofilaments by dip custom-built continuous liquid film coating machine with coating processes using UV-curable PU dispersions. Clean surfaces within the multi-step/multilayer processing CONCLUSIONS were found to be a key parameter. We have achieved Conductive plasma-metallized fibers were successfully coating thicknesses as thin as 800 nm using a pure PU produced and dip-coated with UV-curable PU dispersion at the withdrawal speed of 1.5 m/min (Figure dispersions. Micro- and nanoscale coatings with good 2). insulation and mechanical properties, essential for integration of these e-fibers in textiles, are obtained. Overjacketing extrusion is a promising complementary method to dip coating, extending the range to higher coating thicknesses.

Melt-spinning of bicomponent monofilaments proved to be a promising way to produce POFs that can be integrated into textiles using standard weaving, knitting or embroidery techniques. These POFs enable the development of highly flexible fabrics for sensing and irradiation applications. In combination with the electrically conductive fibers, these core textile modules enable the design and manufacturing of truly wearable functional clothes.

KEYWORDS Smart textiles, POF, bicomponent fibers, metallized

fibers, dip coating, overjacketing extrusion Figure 2: Polyurethane coating on metallized synthetic fibers for insulation and protection. ACKNOWLEDGMENT This research was funded in part through a grant by Although the UV cured coatings have good overall NanoTera (TecInTex), Switzerland. The authors thank M. properties, there are some inherent restrictions of the dip Amberg, P. Barbadoro, S. Ganu, J. Gschwend, M. coating process in terms of velocity range, achievable Rothmaier, P. Rupper, B. Selm and B. Wüst of EMPA, St. coating thickness, polymer types and multifilament Gallen, for their help and efforts in this research. coating. Overjacketing extrusion has the potential to overcome these limitations, which makes it a very REFERENCES promising complementary method to dip coating. In [1] M. Amberg, et al., "Electromechanical Behavior of contrast to the dip coating procedure, a higher coating Nanoscale Silver Coatings on PET Fibers". Plasma velocity leads to thinner coatings, giving the possibility to Processes and Polymers, Vol. 5, No. 9, pp 874-880, achieve thin coatings even at high velocity, or thick 2008. coatings also at low velocity. [2] Z.L. Yang, et al., "Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene- We succeeded in producing highly flexible bicomponent terminated polyurethane aqueous dispersions POFs on a melt-spinning plant. The o-fibers can for mixtures: Preparation and characterization". Polymer, example be applied as near-to-body sensors for Vol. 50, No. 7, pp 1717-1722, 2009. monitoring functions. Due to irregularities in the core- [3] D.V. Rosato, "Extruding Plastics - A practical sheath interface, the light attenuation is still too high processing handbook", Chapman & Hall, London, pp (around 10 dB/m). There is ongoing work to overcome 469-493, 1998. this problem. [4] B. Selm, et al., "Polymeric Optical Fiber Fabrics for Illumination and Sensorial Applications in Textiles". Two different sensors based on o-textiles were developed. Journal of Intelligent Material Systems and The first sensor principle is a pressure sensor in which Structures, Vol. 21, No. 11, pp 1061-1071, 2010. POFs were integrated into an atlas weave. Due to the [5] D. Hegemann, et al., "Recent developments in Ag rubbery material property of the POFs, the fiber cross- metallised textiles using plasma sputtering". section changed under pressure, disrupting light Materials Technology, Vol. 24, No. 1, pp 41-45, transmission. As a result we could produce a location- 2009. dependent touch- and pressure-sensitive fabric. The [6] R. Hufenus, et al., "Biodegradable Bicomponent second sensor principle was realized using woven and Fibers from Renewable Sources: Melt-Spinning of embroidered samples of POFs to build a wearable pulse Poly(lactic acid) and Poly[(3-hydroxybutyrate)-co-(3- oximeter inside a cotton glove. Light with two different hydroxyvalerate)]". Macromolecular Materials and wavelengths was used to measure the oxygenated and the Engineering, Vol. 297, No. 1, pp 75-84, 2012. deoxygenated hemoglobin, respectively.

Electrical Conductivity of Electrospun Polyaniline and Polyaniline-Blend Fibers and Mats

Yuxi Zhang, Gregory C. Rutledge Department of Chemical Engineering, Massachusetts Institute of Technology [email protected]

INTRODUCTION We have used a reliable and sensitive characterization Electrospinning is a convenient method [1] to produce method to accurately determine the electrical conductivity polymer nanofibers with controlled diameters on the order of single electrospun polyaniline fibers. Aligned of tens of nanometers to microns [2]. The resulting electrospun fibers were deposited directly on the nonwoven fiber mats have large surface-area-to-weight interdigitated Pt electrodes (IDE, ABTech) and hot- ratios up to 100 m2/g. Combined with the high electrical pressed. Solartron 1260/1287A high-impedance conductivity of intrinsically conductive polymers, analyzers were used to measure the resistance on the IDE, conductive electrospun fiber mats are promising for a R. The number of parallel pathways N was estimated variety of applications, such as multifunctional textiles, from optical microscope images, and average fiber resistance-based sensors, flexible reversibly hydrophobic diameter d from SEM images. The finger spacings δ were surfaces, organic photovoltaics, and conductive substrates varied to extrapolate the contribution of the contact for surface functionalization and modifications [3]. resistances. The electrical conductivity of the single fibers were calculated based on Equation (1). 1 Polyaniline (PAni) is one of the most studied yet hard-to- 2 14()RN d /4  (1) process electrically conductive polymers, as the elasticity     dRN2 of its solutions is generally insufficient to be directly  electrospun into fibers. One way to solve the problem is to blend high-molecular-weight non-conducting polymers Electrical measurements were also performed on both with the conductive polymers to make the solution randomly-oriented and aligned electrospun fiber mats, electrospinnable [4], but the resulting fibers have much independently, with contact-resistance corrections. lower conductivity due to the blending. Coaxial electrospinning technique can be employed to make fibers with conductive polymers in the core and non-conducting RESULTS AND DISCUSSION polymers in the shell as processing aids [5]. With the PAni blended with PEO (Mw = 1,000,000 and 2,000,000) selective removal of the shell component of the resulting was readily electrospun into fibers in the range of 11 to 67 fibers, pure component electrospun fibers can be formed wt% PAni in the final fibers. PAni blended with PMMA from fluids that are otherwise non-electrospinnable. (Mw = 540,000 and 960,000) was electrospun from its chloroform solution to form fibers with 3 to 25 wt% PAni in the fibers. APPROACH PAni (Sigma-Aldrich, Mw = 65,000) with equimolar The core-shell PAni-PMMA fibers were electrospun amount of (+)-camphor-10-sulfonic acid (Fluka) were under various core and shell fluid flow rates. After dissolved in chloroform and dimethylformamide (DMF), dissolution of the mats and fibers by isopropyl alcohol, ranging from 0.5 to 2 wt%, and blended with either the fiber surfaces were still mostly smooth, as shown in poly(ethylene oxide) (PEO) or poly(methyl methacrylate) representative SEM images in Figure 1. (PMMA) to form a blended solution.

For coaxial electrospinning, the core fluid was 2 wt% PAni with equimolar amount of (+)-camphor-10-sulfonic acid in mixed Chloroform/DMF; the shell fluid was 15 wt% PMMA (Scientific Polymer) in DMF. The shell of the resultant fiber mats were dissolved using isopropyl alcohol to leave behind pure PAni fiber cores.

To increase the molecular orientation within the fibers, FIGURE 1. SEM images of electrospun PAni-PMMA core-shell fibers the core-shell fibers were post-processed by solid-state before (left) and after (right) dissolution of PMMA by isopropyl alcohol; drawing along the fiber axes. This was achieved by first taken under 12,000× magnification (scale bar = 1 μm). electrospinning fibers in an oriented fashion between two The fiber electrical conductivities of the electrospun parallel electrodes under compression and then partially polyaniline fibers are summarized in Figure 2. The fiber releasing the compression to realize strains. electrical conductivities are found to be increasing exponentially with the weight percent of doped distribution within mats, and fiber-fiber contacts in mats. polyaniline in the fibers for both the PAni-PEO systems We arrive at the correlation shown in Equation (2). and the PAni-PMMA systems. The highest electrical calc odf (2) mff(1 )  (1 ) 1 l conductivity achieved at 100% PAni fiber is found to be The results shown in Figure 2 suggest that the model 50 ± 30 S/cm. predicts the mat conductivity quite well. [6]

FIGURE 2. Electrical conductivity of electrospun polyaniline fibers (doped with equimolar amount of (+)-camphor-10-sulfonic acid) as a function of its weight fraction in blended fibers; the pure PAni fiber was obtained after dissolving the shell component (PMMA) of the core-shell fibers. FIGURE 4. Parity plot of the experimentally-observed mat conductivity Solid-state drawing of the aligned 100% PAni fibers in versus that calculated by the model for PAni-blend and PAni fibers. the fiber direction up to 100% strain increases the conductivity to 130 ± 40 S/cm. The most likely cause of this increase is the enhanced molecular orientation in the CONCLUSIONS electrospun fibers along the fiber direction, supported by We have fabricated electrospun PAni fibers over a range the polarized FTIR measurements leading to Figure 3. of compositions in blended fibers. Pure conductive PAni fibers have been produced by coaxial electrospinning and subsequent removal of the shell PMMA. The conductivities of the PAni-blend fibers are found to increase exponentially with the weight percent of doped PAni in the fibers, to as high as 50 ± 30 S/cm for pure as- spun, and to 130 ± 40 S/cm upon solid-state drawing. Using a model that accounts for the effects of intrinsic fiber conductivity (including both composition and molecular orientation), mat porosity, and the fiber orientation distribution within the mat, calculated mat conductivities are obtained in quantitative agreement with the mat conductivities measured experimentally.

REFERENCES [1] Fridrikh, S.V., J.H. Yu, M.P. Brenner, G.C. Rutledge, FIGURE 3. Electrical conductivity of the pure polyaniline fiber, as-spun Phys. Rev. Lett. 90 (2003), 144502. and after solid-state drawing, as a function of molecular orientation within the fibers, as measured by polarized FTIR from aligned fiber [2] Shin, Y.M., M.M. Hohman, M.P. Brenner, G.C. bundles; the label next to each data point shows the corresponding Rutledge, Appl. Phys. Lett. 78 (2001), 1149-1151. nominal strain. [3] Krupenkin, T.N., J.A.Taylor, E.N. Wang, P. Kolodner, M. Hodes, T.Salamon, Langmuir 23 (2007), 9128-9133. The trend in conductivity of the mats with composition is [4] Norris, I.D., M.M. Shaker, F.K. Ko, A.G. very similar to that observed for the fibers, but the values MacDiarmid, Synth. Met. 114 (2000), 109-114. are lower by an order of magnitude or more. In order to [5] Yu, J.H., S.V. Fridrikh, G.C. Rutledge, Adv. Mater. 16 reconcile these differences, we consider the effect of (2004) 1562-1566. several factors, such as fiber composition, fiber [6] Zhang, Y., G.C. Rutledge, Macromolecules 45 (2012), microstructure, fiber curl, mat porosity, fiber orientation 4238-4246.

Mechanical and Electrical Properties of Polyamide 66 Nanocomposites Reinforced with Buckminster Fullerene C60

Ikilem Gocek1, Reyhan Keskin2, Guralp Ozkoc3, Koray Yilmaz4, and Yunus Kamac4 1Istanbul Technical University, Dept. of Textile Engineering, Istanbul, Turkey 2Pamukkale University, Dept. of Textile Engineering, Denizli, Turkey 3Kocaeli University, Dept. of Chemical Engineering, Kocaeli, Turkey 4Pamukkale University, Dept. of Physics, Denizli, Turkey [email protected]

ABSTRACT The aim of this study is to determine the effects of The matrix used in the study is Polyamide 66 (PA66) Buckminster fullerene (C60) addition on Polyamide 66 (Eplon® nylon resins) and the reinforcer is Buckminster (PA66) matrix. Tensile tests are conducted to determine fullerene for the samples. The purity of the Buckminster the mechanical properties of injection molded samples, fullerene used in the study is 99%. Nanocomposites and electrical conductivity tests are conducted to find the produced have fullerene concentrations at 1%, 2 % and electrical conductivity properties of samples produced. 3% wt percentages. Pure samples consisting of 100% PA66 are produced to evaluate the effect of fullerene INTRODUCTION reinforcement to the matrix. Sample codes and their Fullerenes were first synthesized in 1980 by Curl R.F. and matrix and reinforcer contents are given in Table 1. his team in Rice University. Fullerenes are special allotropes of carbon as a macromolecule which consists of Tensile strength tests are conducted on a universal testing sixty or more carbons forming a hollow sphere machine (Lloyd LC, 5kN) at 10 mm/min speed and 25 resembling a soccer ball with sides in pentagons or mm gauge length. hexagons [1]. Curl R.F. and his team received a Nobel Prize in chemistry 1996 for their fullerene discovery [2]. Electrical conductivity tests are conducted at room Buckminster fullerene (C60) is one of the types of temperature and at 10-3 torr vacuum with a four point fullerenes that consist of 60 carbons. An illustration of fixture on a Keithley 2400 source meter by mounting Buckminster fullerene (C60) is given in Figure 1. wires using silver paste on samples cut at 1cmx1cm dimensions. As the resistivities of the samples are too high, additional temperature dependent conductivity tests are not performed.

Table 1: Codes and percentages of samples used in the study. Sample PA66 Fullerene code (wt %) (wt %) PA 100 0 PAFL1 99 1 PAFL2 98 2 Figure 1: An illustration of Buckminster fullerene (C60). PAFL3 97 3 Fullerenes find application in many areas such as medicine, energy, environment, communication, photo devices and electrical devices (ex: superconductivity circuits) [3]. Fullerenes are used in metallic matrices [4], RESULTS AND DISCUSSION high energy storage batteries [5], solar cells and semi- Tensile stress-strain curves for samples are given in conductors [6, 7], flame-retardant applications [8] and as Figure 2. The addition of fullerene results in higher tensile well as reinforcers for polymeric matrices [9]. strengths of the samples compared to the pure control sample (sample code: PA). However, the tensile strength APPROACH of sample PAFL3 is lower than the tensile strength of In this work, composites are produced in small dog-bone PAFL2. shapes using laboratory type twin screw extruder (DSM microcompounder) and injection molding machines (DSM microinjection molding machine) respectively. The processing parameters for the extruder are set as 100 rpm at 270° C and for the injection molding machine the parameters are 9 bar pressure, 280° C barrel temperature and 30° C mold temperature. wt% Buckminster fullerene (PAFL3) might be due to low dispersion of fullerene molecules in the samples.

FUTURE WORK Thermal analysis and X-ray analysis will be conducted to determine the degradation temperature and crystallinity of Buckminster fullerene reinforced composites. Ultrasonication will be applied in different powers and time ranges to increase the dispersion of fullerene particles in the matrix.

REFERENCES [1] Thostenson E.T., Ren Z., Chou T-W., Advances in the Figure 2: Stress-strain curves of fullerene reinforced PA66 composites. Science and Technology of Carbon Nanotubes and Their Composites: A Review, Composites Science and Technology, 61, 13, (2001). Polyamide 66 is an insulator polymer which means that it [2]http://www.nobelprize.org/nobel_prizes/chemistry/laureat does not conduct electricity. The conductivity tests were es/1996/, The Official Web Site of the Nobel Prize. -3 performed only at room temperature and at 10 torr [3] Murayama H., Tomonoh S., Alford J.M., Karpuk M.E., vacuum. The electrical conductivity test results are given Fullerene Production in Tons and More: From Science to in Figure 3. The addition of Buckminster fullerene into Industry, Fullerenes, Nanotubes and Carbon Structures, 12, the matrix adds conductivity to the samples. Even though 1-2, (2005). addition of fullerene increases the conductivity of the [4] Balch A.L., Olmstead M.M., Reactions of Transition samples, a decrease is observed between PAFL2 and Metal Complexes with Fullerenes (C 60, C70, etc) and PAFL3. Related Materials, Chemical Reviews, 98, 6, (1998). [5] Baum R.M., Fullerene Bioactivity: C60 Derivative Inhibits AIDS Viruses, Chemical and Engineering News, 71, 48, (1993). [6] Murayama H., Tomonoh S., Alford J.M., Karpuk M.E., Fullerene Production in Tons and More: From Science to Industry, Fullerenes, Nanotubes and Carbon Nanostructures, 12, 1, (2004). [7] Churilov G.N., Plasma Synthesis of Fullerenes (Review), Instruments and Experimental Techniques, 43, 1, (2000). [8] Loutfy R.O., Wexler E.M., Ablative and Flame-Retardant Properties of Fullerenes, Perspectives of Fullerene Nanotechnology, Part 6, pg 275-280, (2002). [9] Ogasawara T., Ishida Y., Kasai T., Mechanical Properties of Carbon Fiber/Fullerene-Dispersed Epoxy Composites, Composites Science and Technology, 69, 11-12, (2009). [10] Ginzburg B.M., Melenevskaya E.Y., Novoselova A.V., Figure 3: Electrical conductivity of fullerene reinforced PA66 Pozdnyakov A.O., Pozdnyakov O.F., Redkov B.P., Smimov composites. A.S., Shepelevskii A.A., Shibaev L.A., Shiryaeva O.A., Structure of Fullerene C-60 in a Poly(methyl methacrylate) Matrix, Polymer Science Series A, 46, 2, (2004). CONCLUSIONS [11] Alekseeva O.V., Bagrovskaya, N. A., Kuz'min S. M., Addition of Buckminster fullerene into PA66 matrix Noskov A.V., Melikhov I.V., Rudin V.N., The Influence of increases both tensile strengths and electrical Fullerene Additives on the Structure of Polystyrene Films, conductivities of samples compared to pure samples. But Russian Journal of Physical Chemistry A, 83, 7, (2009). a decrease at 3 wt% fullerene addition is observed both in ACKNOWLEDGEMENT tensile strength and electrical conductivity properties of This research is supported by Pamukkale University the samples. Department of Scientific Researches (Pau BAP) on project 2011BSP019, which is appreciated. One of the challenges of processing fullerenes is their tendency to agglomerate [10, 11], The decrease in tensile Special thanks go to Yunus Kamac for his helpfulness in strength and electrical conductivity of samples having 3 performing the electrical conductivity tests and in interpreting test results.

Production of Polymer Filament-Shaped Piezoelectric Sensors for E-Textiles Applications

R.S. Martins1, R. Gonçalves2, J.G. Rocha3, J.M. Nóbrega1, H. Carvalho4, S. Lanceros-Mendez2, 5 1IPC/I3N-Institute for Polymers and Composites; 2Centro/Departamento de Física; 3Dep. Industrial Electronics; 4Centre for Textile Science and Technology, University of Minho; 5INL-International Iberian Nanotechnology Laboratory, Portugal [email protected]

INTRODUCTION PVDF-based sensors are available on the market in the This work aims at the development of piezoelectric form of films. In this case, a thin PVDF layer is deposited materials for flexible sensors produced with various with electrode layers on both sides, normally by geometries, at low cost and high production rates, metallization or sputtering. Some research work has adequate for the industrial scale. In particular the filament targeted the development of PVDF sensors in form, appropriate for integration into textiles, is filament/cable form. The filament-shaped piezoelectric described, but other geometries, such as tape, are also sensor for textile applications should be arranged in a being studied. The filaments are produced by co-extrusion coaxial manner, as shown in figure 1. of multiple layers with piezoelectric and electrically conductive polymer composites.

In the last years, many researchers and also some industrial enterprises have put large effort studying the integration of systems and devices into textile products [1,2]. This integration normally requires separate industrial processes for the textile and the device. Preferably, functional fibres providing a more significant part or even the complete solution for a given application should be used. In this work, the production and testing of Figure 1: Layer arrangement for piezoelectric filament filaments working as mechanical sensors is presented. Several authors have studied different aspects related to PIEZOELECTRIC POLYMERS AND THEIR the production of such filaments. Vatansever et al [7] APPLICATION IN TEXTILES reported on the production of simple PVDF Poly(vinylidene fluoride) (PVDF) is a polymer that has monofilaments which are stretched and poled inline by an been extensively studied due to its piezoelectric electric field produced between two parallel plates. properties. These properties depend on the degree of Walter et al [8] have extensively studied the phase crystallinity, structure and orientation of the polymer transitions in extruded PVDF monofilaments and crystalline fraction, which, in turn, depends on the produced a piezoelectric composite based on processing conditions [3]. The piezoelectric properties of monofilaments. Mazurek et al [9] described the the polymer can be useful in applications such as sensor production of concentric piezoelectric cables by co- and actuator devices. extrusion and sequential processing.

PVDF presents at least 4 crystalline phases. The non- The use of conductive polymer composites for creation of polar α-phase is obtained by crystallization from the melt the electrodes has been studied in previous work [10]. [3]. The β-phase is the most interesting form the point of PVDF filament has been co-extruded with a view of the electroactive activity, and results optimally Polyproplylene/Carbon Black conductive inner core and a from stretching α-PVDF at 80ºC using a stretch ratio (R) PVDF outer layer, and it has been shown that the between 3 and 5 [4,5]. The molecular chains are thus electroactive phase content is not affected by the aligned. Further, a poling process is carried out through conductive inner core, depending only on the processing the application of a strong electrical field to the PVDF temperature and stretch ratio, as previously found for layer [6]. After poling, the polymer has an optimal single filaments. Similar work has been described by piezoelectric response. This means that an electrical Lund and Hagström in [11]. potential will be produced upon mechanical excitation of the polymer, or a mechanical action is produced in the DEVELOPMENT AND TEST polymer when it is subjected to an electric field. To In this work, two and three-layer filaments incorporating measure this electrical potential (or to apply voltage to the electrically conductive layers as electrodes and a polymer), electrodes making up equipotential surfaces piezoelectric layer, in a coaxial arrangement, are have to be provided, at which the voltage produced by the produced using conventional polymer extrusion polymer (applied to the polymer) can be connected to equipment. The process is presented in figure 2 adequate signal conditioning (drive equipment). CONCLUSIONS Multilayered all-polymer filaments that exhibit piezoelectric behavior have been produced through an industrial scalable methodology based on co-extrusion. Figure 2: Schematic view of the production process ACKNOWLEDGMENTS The conductive layers are produced using a commercial The authors thank the Portuguese Foundation for Science PP/carbon black composite polymer (Pre-Elec Premix and Technology (FCT) for financial support under PDTC 1396). In the case of two-layered filaments, the outer (PTDC/CTM/108801/2008) electrode is achieved by painting the filament with conductive silver ink. Poling is accomplished by applying REFERENCES high voltage (in the order of 10 kV) directly connected 1. D. Meoli, T. May-Plumlee, Interactive electronic textile between the inner and the outer electrodes. Variable development- A review of technologies, Journal of periods of time and poling temperatures were studied in Textile and Apparel, Technology and Management, Vol.2, order to optimize the piezoelectric response. Issue 2,(2002). 2. J. Edmison, M. Jones, Z. Nakad, and T. Martin, Using The filaments are then connected to a charge amplifier piezoelectric materials for wearable electronic textiles, and the signals are acquired with a data acquisition board Sixth International Symposium on Wearable Computing, and a computational application developed in Labview. ISWC 2002, pp 41–48, (2002). Piezoelectric activity is tested by applying mechanical 3. J. Lovinger, Developments in crystalline polymers, action, either using a vibration generator to produce cyclic Elsevier Applied science, London (1982). bending deformation, or using a universal testing machine 4. J. Gomes, J. Serrado Nunes, V. Sencadas and S. to deform the filament in an extensional manner. Lanceros-Mendez, Smart Materials and Structures, 19 (6) (2010) 065010. RESULTS 5. V. Sencadas, R. G. Jr. and S. Lanceros-Mendez, Journal To achieve stable production conditions for both 2 and 3- of Macromolecular Science, Part B: Physics 48 (2009), p. layered filaments, the experimental conditions have to be 514. optimized for the specific equipment and materials used 6. Dickens B, Balizer E, DeReggi AS, Roth SC. Hysteresis in order to optimize the α-to-β phase transition. β-phase measurements of remanent polarization and coercive field content larger than 70% were obtained in the PVDF in polymers. J Appl Phys 1992;72:4258. layer. Piezoelectric activity has been shown and depends 7. D.Vatansever, R. L. Hadimani . T. Shah, E. Siores, on the processing and poling conditions. Figure 3 shows a Piezoelectric Mono·Filament Extrusion for Green Energy signal acquired by applying traction stress with a Applications from Textiles, International Congress of universal testing machine (1mm extension of a 10 cm Innovative Textiles, ICONTEX2011, Istanbul, (2011). long filament at a frequency of about 1 Hz). 8. S. Walter, W. Steinmann, J. Schütte, G. Seide, T. Gries, G. Roth, P. Wierach and M. Sinapius, “Characterisation of piezoelectric PVDF monofilaments,” Materials Technology: Advanced Performance Materials, vol. 26, no. 3, (2011) pp. 140–145. 9. B. Mazurek, S. Różecki, D. Kowalczyk, T. Janiczek, Influence of piezoelectric cable processing steps on PVDF beta phase content, Journal of Electrostatics, Volumes 51-52, Elsevier B.V. pp 180-185 (2001). 10. A. Ferreira, P. Costa, H. Carvalho, J.M. Nóbrega, V. Sencadas, S. Lanceros-Mendez, Extrusion of poly(vinylidene fluoride) filaments: effect of the processing conditions and conductive inner core on the electroactive phase content and mechanical properties, Journal of Polymer Research, Springer, Netherlands, Doi: Figure 3: Output at the charge amplifier (amplitude about 10.1007/s10965-011-9570-1 (2011). 250mV) 11. A. Lund, B. Hagström, Melt Spinning of b-Phase Poly(vinylidene fluoride) Yarns With and Without a Conductive Core, Journal of Applied Polymer Science,Vol. 120, 1080–1089 (2011).

Chemical Resistance of Poly(3,4-ethylenedioxythiophene) on Textiles

Jinlin Cai, Christopher DiFranco, Qinguo Fan Dept. of Bioengineering, UMass Dartmouth, MA, 02747 [email protected]

ABSTRACT and after chemical treatments. The morphological The chemical resistance of Poly-3,4- changes after 72hr treatments were studied by ethylenedioxythiophene (PEDOT) was tested in both scanning electron microscope (SEM). The PEDOT organic and inorganic solvents including sodium coated fabrics demonstrated excellent chemical hydroxide, cyclohexanone, tetrahydrofuran (THF), resistant properties since its electrical resistance 91% isopropyl alcohol and dimethyl sulfoxide maintained on the order of magnitude of 1000 Ohm (DMSO). PEDOT was synthesized by the vapor after treatment in almost all of the solvents except for phase polymerization process and coated on 10% NaOH and THF which had a large increase of PET/cotton, cotton, and polyester textile substrates. electrical resistance which occurred due to the The electrical resistance of the PEDOT was measured disappearing PEDOT coating from the substrate both before and after the chemical treatments. The indicating their potential to be a good solvent for morphological changes after treatment were studied PEDOT. by using the scanning electron microscope (SEM). The PEDOT coated fabrics demonstrated good EXPERIMENTAL chemical resistant properties in most of the chemicals Materials even after 72hrs treatment except NaOH and THF.  Vapor Phase Polymerization of PEDOT The increasing of electrical resistance for NaOH 3,4-Ethylenedioxythiophene (EDOT) treated samples varied from 10 times to 1000 times monomer, (Sigma Aldrich) which well corresponds to the breaking down of (Fe(III) tosylate),40% in Butanol (Heraeus) PEDOT layers from the substrate after treatment as Pyridine 99.8% (Fluka) observed from the SEM. While after 48hrs treatment Poly(ethylene glycol) PEG Average of THF, the PEDOT layers were visibly disappearing M.W.400 (Sigma Aldrich) from the substrate following the total loss of  Solvents: electrical property which indicates the potential of NaOH 97% pellets (Acros Organics) THF as a good solvent for PEDOT coated on textiles. Cyclohexanone 99.8% (Acros Organics) Tetrahydrofuran (Fisher Scientific) KEYWORDS 91% Isopropyl alchohol (Vi-jon) conducting polymer, chemical resistance, conducting Dimethylsulfoxide DMSO 99.7% (Acros textiles, PEDOT Organics)  Fabrics, testfabrics INTRODUCTION Poly/Cot: 50/50, Lab Among conducting polymers, PEDOT is significantly Cotton #441 important due to its small band gap, high PET #700-2 conductivity and high stability. In particular, the Methods and Instruments small band gap structure enables it to be utilized in  Vapor Phase Polymerization of PEDOT several applications such as organic light emitting  Morphological changes inspected by Joel diodes, photovoltaic’s, electroluminescent devices, JSM 5610 Scanning Electron Microscope antistatic coatings and capacitors[1]. The chemical (SEM) resistance of Poly-3,4-ethylenedioxythiophene  Quincy Lab Inc. AF Model 40 Lab Oven set (PEDOT) was tested in both organic and inorganic at 100°C solvents including 10% sodium hydroxide,  Resistance Measured according to AATCC cyclohexanone, tetrahydrofuran (THF), 91% Test Method 76-2005. Isopropyl alcohol and dimethyl sulfoxide (DMSO). o Extech Instruments Multipro 530 PEDOT was synthesized via the vapor-phase True RMS Multimeter polymerization process and coated on PET/cotton, o Pony 3202 Clamps cotton and polyester textile substrates. Electrical  To test resistance before and after treatment resistance of the PEDOT was measured both before electrodes were formed on a rigid surface, and the firm contact between the electrodes increase in resistance was 8 times from the and the fabric was provided by high pressure initial resistance. clamps.  We observed a drop in resistance at 48hrs to about 4 times the initial resistance. RESULTS AND DISCUSSION  In THF, PEDOT resistance only increased Cotton Substrate roughly 8 times and after observing SEM  10% NaOH showed the most significant images, was clear there was a remaining influence on changing the electrical layer of PEDOT on the substrate. resistance of PEDOT. After 72hr treatment  The remaining solvents had increases the resistance increased over 8 times. between 3-10 times their initial resistances.  In THF, PEDOT almost lost its electrical  The weight loss of the samples corresponds conductivity after 24hr treatment, the with their decreases in electrical conductive layer was removed from the conductivity with 10% NaOH having also cotton substrate after 48hr and after 72hr the greatest weight loss after 72 hr treatment there was no remaining PEDOT available on  The SEM pictures show most of the PEDOT the substrate to test resistance or weight. has been removed in 10% NaOH while still  For the remaining solvents the electrical some remains in THF resistance increased around 2-4 times after 72hrs and most of the conductive layer was CONCLUSIONS left on the substrate.  The PEDOT coated fabrics demonstrated  Weight loss of each samples are excellent chemical resistance because it corresponding to their decrease of electrical maintained on the order of magnitude of conductivity 100ohm after treatment in almost all of the  From analyzing the SEM pictures, textile solvents. structures contained less PEDOT compared  10% NaOH and Tetrahydrofuran (THF) had with untreated substrates. an increase of electrical resistance which occurred due to the disappearing PEDOT Polyester Substrate coating from the substrate which indicates  10% NaOH showed the most significant its potential to be a good solvent for PEDOT. influence on changing the electrical resistance. After 72hr treatment the ACKNOWLEDGMENT resistance increased almost 7,000 times. Authors would like to thank Dr. Chen-Lu Yang,  In THF, PEDOT did actually lose its Advanced Technology and Manufacturing Center electrical conductivity after 24hr and there (ATMC), University of Massachusetts Dartmouth was no more PEDOT remaining on the and Serkan Yildiz, graduate student for their valuable substrate. input and technical assistance.  The remaining solvents had changes of electrical resistance between 2-10 times with REFERENCES the exception of 91% Isopropyl alcohol 1. T.A. Skotheim, J.R. Reynolds, Handbook of which experienced a change of about 256 Conducting Polymers: Theory, Synthesis, times its initial resistance. Properties and Characterization, CRC, s:  For weight loss of the samples treated 10% 1420043587, pp. 10-1, 2006. NaOH had significant weight decrease after 2. B. Winter-Jensen, K. West, Vapor-Phase 72hrs Polymerization of 3,4-  The SEM pictures show the PEDOT Ethylenedioxythiophene:A Route to Highly conductive layer was mostly removed after Conducting Polymer Surface Layers, 72 hrs treatment Macromolecules, vol: 37, pp. 4538-4543, 2004. For Poly/Cotton Substrate 3. Catarina Carlberg, Xiwen Chen, Olle  10% NaOH showed the most significant Inganas. Ionic Transport and Electronic influence on changing the electrical Structure in Poly(3,4- resistance. After 24hr treatment the ethylenedioxythiophene). Solid State Ionics. resistance increased by almost 11 times 85(1996): pp. 73-78. however after 72hr treatment the final

Tuneable Force Sensor Based on Flexible Polymeric Optical Fibres

Marek Krehel1, 2, René M. Rossi1, Gian-Luca Bona1, 2 and Lukas J. Scherer1

1Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Protection and Physiology, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland; 2ETH Zurich, Swiss Federal Institute of Technology, Department of Information Technology and Electrical Engineering, Gloriastrasse 35, 8092 Zurich, Switzerland Corresponding author: [email protected]

INTRODUCTION Fiber extrusion with melt flow index Optical fibres based sensors have numerous advantages e.g. The transparent light pipes were produced by using a melt flow insensitivity to electromagnetic fields, water and corrosion index apparatus (MFI), model 7085.15a, provided by ZWICK resistance, compact size and small weight [1, 2]. Due to these with an external drawing engine. All tested materials were firstly benefits, optical fibre based sensors are used in numerous dried in the vacuum oven for 8 h at 80 °C. Fibres made of applications to detect chemical as well as physical changes [1, 3- Geniomer 100 were extruded with three different diameters. 6]. Various methods to detect pressure using optical fibres are Since this material showed the best melt flow characteristics of known. Wang et al. proposed a pressure sensor that employs the all three polymers, the diameter of the light pipes could be easily effect of photoelasticity [7]. To implement optical fibre based varied with this polymer. Three different fibre diameters made pressure sensors into fabrics, the fibres should be highly of this material were studied: 0.45mm, 0.75 mm, and 0.85 mm. flexible, which is not the case for the glass-based fibres used for fibre bragg grating based sensors. RESULTS AND DISCUSSION In this study, elastic light pipes, which react to applied pressure Optical properties of extruded optical fibres by deflecting the fibre’s structure are reported. Due to their high The force sensor is based on the losses in light transmission over flexibility and their appropriate tensile strength (from 0.0033 to the light guides when the fibres are compressed. Measured 0.0056 GPa), these fibres are suitable for the incorporation into signal loss varied between 0.16 and 0.25 dB/cm. That means textiles [8, 9]. Intelligent fibres have several advantages that all fibres produced with the MFI apparatus were suitable for compared to textile electronics when wearing them close to the light transmissions over short distances below 1 m. body e.g. comfort, easy of movements, and decreased movement artefacts [8]. Since the electronics often involved in the Intrinsic light absorption spectrum in visible region proposed solutions would negatively influence the haptic of The intrinsic absorption spectrum of the light guide made of these textiles, flexible and smart fibres allow the separation of Geniomer 100-HDS as explained in Experimental Section. Since the rigid electronics from the measured region and thus from the the overall attenuation of the light pipes was much higher, the body. Possible body parameters which could be measured with main light loss was due to extrinsic losses caused by the the proposed solution are e.g. muscles activity, motion extrusion process (irregular fibre surface, bubbles or other detections or breath monitoring [10]. inhomogeneities in the material).

EXPERIMENTAL SECTION All the polymers used were purchased from Wacker Chemie AG. The polymers were all from the Geniomer group and are block-co-polymers containing a soft silicon part and a hard polyurethane part. The light attenuation measurements were performed with the cut-back method at 652 nm [11]. Due to the length of the fibres which were around 1 m, the light was first coupled into a mode mixer in accordance to the Japanese Industrial Standard JIS 6863 and afterwards it was launched into the fibre that was measured. The following equation was used in order to compute the light attenuation [12]. The measurements were conducted five times. Figure 1 Intrinsic losses of the polymer Geniomer 100-HDS

Force sensing Applied force resulted in an elliptical deformation of the fibre

cross section. From the side projection a cavity was observed. Where: I – Input light intensity, I0- Output light intensity This deflection increased the out-coupling of the light in the Intrinsic losses over a whole visible spectrum of Geniomer 100 pressed area due to the geometrical deformation of the fibre. were performed using the photospectrometer UV-VIS Since the degree of deflection was directly related to the applied Lambda900 provided by Perkin Elmer. The spectrometer force, the force could be quantitatively assigned. measures continuously and independently (by means of beam From the strain-stress curve it can be concluded that the fibre splitting) the intensity of the reference beam and uses this to made of Geniomer 175 has smaller elastic modulus than the compute reflection or transmission coefficients. In order to fibres made of the other two Geniomers and thus should have determine the intrinsic loss of the polymers, a polymer cube the highest response for applied pressure. The Young moduli of with the dimension 50 x 10 x 5 mm was formed. Geniomer 100 and Geniomer 100-HDS are similar and big differences in the light transmission could not be observed while CONCLUSION pressure was applied. We propose a simple way to manufacture force sensors based on The force sensing experiment was conducted with the 3 different light pipes. The working principle of the sensor is the use of the types of fibre materials. Depending on the material used for deflection of the fibre structure when a force is applied. By extrusion, the applied forces caused different responses in light using materials with different young’s modulus, the sensitivity transmission. This was expected due to the different yield of the material can be tuned according to the desired application strength shown. As shown in Figure 2 Geniomer 100-HDS in the range of 0.05–40 N over 3 cm. The fibres produced from showed full reversibility up to 20 N and was therefore the Geniomer 175 are best suited for low forces, while the material which was best suited for high forces. At the level of 30 Geniomer 100-HDS fibres are ideal sensors for higher forces. N the signal went back to 95.8% ±1.1 %. Although the fibre did Moreover, due to the flexibility and the high mechanical not relax completely at 30 N and 40 N, the measured signal after strength of the material, the proposed sensor can be easily applying pressure was fully repeatable (σ=0.0%) at these forces. integrated into textiles to form textile-based force sensors with possible applications as seat occupation monitoring in automotive or aeroplanes or as force sensor for medical applications (prevention for decubitus or breathing monitoring). Since the flexible fibres and not the electronics have to be placed on the measuring place, this sensing principle has no negative influence on the flexibility and the haptic of the textile. Since only one wavelength is used for the measurement, a simple electronic system consisting of a LED and a photo detector like e.g. photodiode can be used.

REFERENCES 1. Giallorenzi, T.G., et al., Optical Fiber Sensor Technology. Ieee Journal of Quantum Electronics, 1982. 18(4): p. 626-665. Figure 2 Pressure influence on the fibre made out of Geniomer 2. Liehr, S., et al., Polymer Optical Fiber Sensors for Distributed 100-HDS with a diameter of 0.5 mm. Each force was Strain Measurement and Application in Structural Health applied/released three times. Monitoring. Ieee Sensors Journal, 2009. 9(11): p. 1330-1338. 3. Ding, J.Y., M.R. Shahriari, and G.H. Sigel, Fiber Optic Ph Geniomer 100 and Geniomer 175 showed plastic deformation Sensors Prepared by Sol-Gel Immobilization Technique. already at 10 N. Consequently, Geniomer 100 did only reach Electronics Letters, 1991. 27(17): p. 1560-1562. 91%±2.5% of the initial signal after releasing from 10 N and 4. Rothmaier, M., et al., Photonic textiles for pulse oximetry. was therefore the material with the lowest applicable forces for Optics Express, 2008. 16(17): p. 12973-12986. the sensing system. 5. Witt, J., et al., Medical Textiles With Embedded Fiber Optic The sensitivity of the applied force on the fibre deflection is Sensors for Monitoring of Respiratory Movement. Ieee Sensors related to the young’s modulus of the material. The fibre made Journal, 2012. 12(1): p. 246-254. of Geniomer 175 had the highest response to applied. The drop 6. Rantala, J., J. Hannikainen, and J. Vanhala, Fiber optic in the signal of 20.8%±0.5% for 1 N was twice higher for the sensors for wearable applications. Personal and Ubiquitous fibres produced from Geniomer 175 than the fibres produced Computing, 2011. 15(1): p. 85-96. from Geniomer 100 and Geniomer 100-HDS. Geniomer 175 7. Wang, A.B., et al., Optical Fiber Pressure Sensor Based on was chosen for measureing the smallest forces, ranging from Photoelasticity and Its Application. Journal of Lightwave 0.05 N to 0.5 N. All the measured forces were successfully Technology, 1992. 10(10): p. 1466-1472. detected and the measurements were fully repeatable (σ=0.0%). 8. Rothmaier, M., Textile Pressure Sensor Made of Flexible The smallest detectable force was 0.05 N. Plastic Optical fibers. Sensors, 2008: p. 4319-4329. Fibre’s diameter influence on the sensitivity was measured with 9. Selm, B., et al., Polymeric Optical Fiber Fabrics for Geniomer 100. By decreasing the fibre diameter, the fibres Illumination and Sensorial Applications in Textiles. Journal of became more sensitive to the applied force. The fibre with the Intelligent Material Systems and Structures, 2010. 21(11): p. diameter of 0.85 mm was not sensitive enough at low forces (1 1061-1071. N) to get accurate and repeatable values. However, forces up to 10. Meyer, J., P. Lukowicz, and G. Troster, Textile pressure 40 N could be measured reversibly, while the thinnest fibre sensor for muscle activity and motion detection. Tenth Ieee (0.45 mm) could only be used for forces up to 10 N. International Symposium on Wearable Computers, Proceedings, 2006: p. 69-72. Fibre deflection against signal drop 11. Ziemann, O., et al., POF-Handbook. 2008, Berlin: Springer. The relative fibre deflections in the force direction versus the 12. Kuzyk, M.G., Polymer Fiber Optics. 2007. p. 97-98. signal drops of all fibres (different polymers and different diameters) were measured. Only the measurements with strictly elastic deformations were taken into account. The measurements of the fibre deflection were performed simultaneously with the force measurements using the tensile testing machine. The measurements clearly showed that that the signal drop is correlated to the fibre deflection, independently of the polymer material and the fibre diameter. This shows that only the deflection in force direction influences the amount of the out- coupled light and that the elastic properties of the material has only a minor influence on the signal change.

Posters

3D Volume Representation of Nanowebs

Zachary R. Dilworth1, Tao Huang1, Praveen Thiagarajan2 1DuPont Central Research and Development, Experimental Station, Wilmington, DE 2DuPont Corporate IT, Wilmington, DE [email protected]

ABSTRACT Figure 1 shows nine images of fibers at different focus As the fiber industry continues to move towards smaller depths over a 50 µm range. Figure 2 shows a 3D volume fibers for better performance in barrier applications, new image reconstructed from 300 images as shown in Figure methods are required to visualize nanowebs. This poster 1. will report on the 3D volume rendering of nanowebs. These images are vital for understanding the fiber orientation and the pore structure represented in 3D nanowebs.

INTRODUCTION The ability to create 3D volume images of microfibers has been made possible by x-ray microtomography. Until now, it has been difficult to create images of nanofibers. The visualization of nanofibers is dominated by SEM (scanning electron microscope) because it delivers superb image clarity at high magnification and has become the industry standard for measuring fiber size. However, SEM and other 2D imaging techniques fail to show how fibers are oriented within a nonwoven article and the geometrical and topological features of nanoweb pore structure. Over the past few years, we have attempted to reconstruct 3D images from a series of tiled SEM images, Figure 1. Nine images at different focus depths over a 50 a stack of dual-beam SEM images, or a stack of confocal µm range. Each image area is 271 µm by 210 µm. images, with very limited success. This poster will report our efforts to create 3D volume renderings of nanowebs through the reconstruction of a stack of images from sub- micron resolution optical microscopy.

EXPERIMENTAL RESULTS Optical microscopy has not been used for imaging nanowebs, due to diffraction-limitations, as well as noise due to scattering. The characterization of sub-wavelength structures using a microscope is difficult because of the Abbe diffraction limit. Light with wavelength λ, traveling in a medium with refractive index n and converging to a spot with angle  will make a spot with radius d=λ/(2nsin ). The denominator (nsin ) is called Figure 2. 3D volume image reconstructed from 300 the numerical aperture (NA) and can reach about 1.4 in images as shown in Figure 1. modern optics. Hence, the Abbe limit is roughly d=λ/2. For green light with wavelength of 500 nm, the Abbe In this study, an image field of three by three was chosen limit is 250 nm. A polymer nanoweb contains nanofibers to increase the sampling area by a factor of about seven, with diameters on the order of 250 nm to 800 nm. An to roughly 271 µm x 210 µm versus 101 µm x 81 µm, optical illumination system with a high-aperture cardioid while still maintaining a manageable file size. annular condenser and a high numerical aperture makes it Individually, these images give little information as to possible to get an image stack of the nanoweb with a high how fibers are structurally related. With the use of megapixel digital camera and precise control of vertical volume rendering software, a stack of images can be resolution (down to 10 nm). transformed into a 3D volume rendering of a nanoweb.

Comparison of Evaporative Resistance of Carbon-Based Chemical Protective Undergarments

Janet Brady1, Timothy Rioux1, Niny Rao1, Carole A. Winterhalter2 1Laboratory for Engineered Human Protection, Philadelphia University, Philadelphia, PA 19144 2U.S. Army Natick Soldier Research Development and Engineering Center, Natick, MA 01760 [email protected]

INTRODUCTION different fit), and 2) comparison to Garment 2 (same fit The Laboratory for Engineered Human Protection different fabric). Thermal resistance comparisons of (LEHP) has developed prototype garments for the Garments 1 through 3 have been previously explored and purpose of improving comfort while protecting war- reported [6]. Garment 4 was produced from Material B fighters against chemical warfare agents. It is important using Design T to complete the thermal and evaporative that the new garment design not compromise the thermal resistance study. Similar to Garment 3, two comparison and evaporative characteristics of the garment. The effects are made with Garment 4, one with Garment 2 to evaluate of clothing material and garment fit on thermal insulation differences observed between garments produced from and evaporative resistance have long been a focus of the same fabric (non-stretch) having different fit (T vs. L) many studies [1, 2, 3, 4]. In this study the effect of fabric and, the final comparison with Garment 1, which stretch and garment fit on evaporative resistance was evaluates differences observed in garments having the investigated using stretch and non-stretch carbon-based same fit (T) produced from two different fabrics (non- fabrics in two garment designs: tight or body conformal, stretch vs. stretch). It should be noted that Garments 3 and and loose. 4 were produced solely for comparison purposes, and the corresponding garment designs were not optimal for each MATERIALS AND METHODS fabric when one considers the fabric mechanical One-piece “union suit” style garments were fabricated properties. Thus we do not compare thermal and from each of the two fabrics. The stretch fabric (Material evaporative properties between Garments 3 and 4. A) was manufactured by Purification Products Limited and made from a polyester blend knit impregnated with Evaporative resistance of each garment was determined activated carbon. The non-stretch fabric (Material B) was using a male form thermal manikin having 34 a laminate composed of activated carbon sandwiched independently heated zones (“Newton,” MTNW Seattle, between a polyester/cotton woven fabric and nylon WA, USA). All zones were heated to 35oC. 100% cotton nonwoven. The mechanical properties of the fabric were underwear, jockey briefs, crew neck T-shirt, and cotton measured using the Kawabata Evaluation System [5]. athletic socks were placed under each garment before Weight (W, oz/sq.yd), elongation (EMT, %), Shear testing. The manikin was also dressed with boots, gloves, Rigidity (G, gf cm-1 degree-1), Hysteresis of shear force at and glove liners. Thermal resistance experiments were 0.5 degrees of shear angle (2HG, gf/cm), Hysteresis of performed in an environmental chamber set to 23 + 0.5oC, shear force at 5 degrees of shear angle (2HG5, gf/cm), 50 + 5%RH, and a wind speed of .4 + .1 m/s in Bending rigidity (B, gf cm-1 degree-1) and Hysteresis of accordance with ASTM F 1291-05. Evaporative bending moment (2HB, gf cm cm1) are shown in Table I. resistance experiments were performed under isothermal conditions at 35 + 0.5oC, 50 + 5%RH, and a wind speed TABLE I. Mechanical Properties of Material A and B of .4 + .1 m/s in accordance with ASTM F 2370-05. For all evaporative resistance tests a tight fitting skin suit was Property Material A Material B placed under the clothing to wick water from the 137 W 8.6 6.74 pores evenly across the body. The sweating rate was EMT 90.82 3.03 controlled at 200 ml/hr-m2. Three replicate measurements G 2.2 6.18 were made on each garment, undressing and redressing 2HG 3.15 8.54 the manikin between each test. Nude manikin tests were 2HG5 4.59 14.99 conducted in the same environmental conditions to B 0.177 0.882 determine the insulation boundary air layer surrounding 2HB 0.119 0.561 the manikin.

The clothing area factor, fcl for each garment was Garment 1 was fabricated from the stretch Material A calculated according to methods outlined previously [6]. which resulted in a tight design (Design T). Garment 2 The total evaporative resistance Re,T was calculated as was constructed with the non-stretch Material B, which outlined in ISO 9920. Together with fcl the intrinsic water resulted in a loose fitting garment (Design L). Garment 3 vapor resistance Re,cl was calculated as follows (ISO was fabricated from Material A using Design L for two 9920): comparisons: 1) to compare to Garment 1 (same fabric differences in R and R values of Design T are Re,a e,T e,cl Re,cl  Re,T  (1) comparable to those of Design L, indicating that these fcl differences are due to the difference in materials. Previous work revealed that a loose-fitting garment Where Re,a is the evaporative resistance of the air layer on exhibited higher evaporative resistance than a tight-fitting the surface of the nude manikin’s sweating surface. garment produced from the same material [4]. In addition, when comparing two different materials, namely Material RESULTS AND DISCUSSION A exhibiting high stretch with reduced bending and shear The evaporative resistance of the garments are listed stiffness as compared to Material B not having any ability below in Table II. to stretch coupled with high bending and shear rigidity; the results indicated that non-stretch, stiffer material Table II. Evaporative Resistance of Garments in SI units exhibited higher evaporative resistance properties. The (m2Pa/W) higher evaporative resistance of garments constructed Garment Material Garment fcl Re,a Re,cl Re,T from Material B were attributed to the lack of drapability Code Design (as indicated by fabric mechanical properties), which 1 A T 1.23 13.6 19.5 30.5 therefore, increased the air layer between the skin and the 2 B L 1.33 13.6 34.5 44.7 garment, resulting in a higher clothing area factor. 3 A L 1.29 13.6 30.8 41.3 CONCLUSIONS 4 B T 1.27 13.6 23.6 34.3 We have confirmed from our results that the evaporative resistance of a garment is determined by both the material Our results indicate that for garments produced from from which it is fabricated and the design of the garment. Material A (Garment 1 vs. Garment 3), the measured total We have found that by altering the design of the garment, evaporative resistance of Garment 3 (Design L) is 26.1% one can alter the evaporative resistance and vice versa. higher than that of Garment 1 (Design T), and the intrinsic evaporative resistance of garment 3 is 37.7% ACKNOWLEDGMENT higher than that of Garment 1. Similarly, for garments This effort was supported through grant W911QY-09-1- produced from Material B (Garment 2 vs. Garment 4), the 0001 from the U.S. Army Natick Soldier Research, measured evaporative resistance of Garment 2 (Design L) Development and Engineering Center. is 23.3% higher than that of Garment 4 (Design T), and the intrinsic evaporative resistance of Garment 2 is 31.6% REFERENCES higher than that of Garment 1. This finding is in [1] McCullough, E.A., Jones, B.W., Zbikowski, J.P., The agreement with the fact that the loose fit Design L effect of garment design on thermal insulation value of garment increases the surface area, thus increasing the clothing, ASHRAE Trans. 89, 327-352 (1983). total evaporative resistance as well as the intrinsic [2] Nielsen, R., Gavhed, D.C.E., Nilsson, H., Thermal evaporative resistance. It is interesting to note that function of a clothing ensemble during work: dependency percent differences in Re,T values and Re,cl values on inner clothing layer fit, Ergonomics 32 (12), 1581- determined using Garments 1 and 3 are comparable to 1594 (1989). those determined using Garments 2 and 4. This suggests [3] Zhang, P., Gong, R.H., influence of clothing material that since the material in each comparison was held properties on rectal temperature in different environ- constant, the percent difference in Re,T values and Re,cl ments, Int. J. Cloth. Sci Tech. 14(5), 299-306(2002). values would arise solely from the difference in garment [4] Chen, Y.S., Fan, J., Qian, X., Zhang, W., Effect of designs, namely Design L and Design T. garment fit on thermal insulation and evaporative resis- tance, Text. Res. J. 74(8), 742-748 (2004). Further examination of the data shows that although [5] Kawabata S., The Development of Objective Garments 1 (Material A) and 4 (Material B) were measurement of fabric handle, Proceedings of the Japan- constructed using the same tight fit Design T, the Australia Joint Symposium on Objective Specification of measured total evaporative resistance values are quite Fabric Quality, Mechanical Properties and Performance, different. The Re,T value for garment 4 is 11% higher Kyoto, Japan, 1982, 31-59. than that of Garment 1 and the intrinsic evaporative [6] Brady J., Rao N., Rioux T., Winterhalter C., resistance for Garment 4 is 17.4% higher than that of Comparison of thermal resistance between two garment Garment 1. Analogous comparison revealed that for designs driven by material characteristics using a thermal loose fit Design L, the Re,T value for Garment 2 is 7.61% heated manikin. Proceedings of the International higher than that of Garment 3 and the intrinsic Conference on Environmental Ergonomics, Boston, MA, evaporative resistance for Garment 2 is 10.7% higher than USA, 2009. that of Garment 3. Again, it is worth noting that percent

Phase Separation to Create Hydrophilic Yet Nonwater Soluble PLA/PLA-b-PEG Fibers via Electrospinning

Larissa Buttaro1, Margaret Frey1, Erin Drufva2 1Cornell University, 2Mount Holyoke College [email protected]

STATEMENT OF PURPOSE Temperature G The goal of this research is to use polymer phase Control Solution in Syringe C separation to create specialized fibers that are Inside Heating hydrophilic yet non-water soluble by electrospinning Chamber from homogeneous solutions. The specific system Fiber studied will be Poly(lacticacid)(PLA)/PLA-b- Poly(ethylene glycol) (PLA-b-PEG) in solvent Force from Dimethylformamide (DMF). The more hydrophilic Pump polymer, PEG should increase in concentration from the center of the fiber to the surface while the more hydrophobic polymer, PLA should increase in concentration from the surface to the center of the fiber. Voltage Heat Gun Source INTRODUCTION Biosensors, tissue scaffolds, filtration membranes, and protective clothing are continually being looked at for improvements in size and functionality. [1-4] Poly(lactic acid) (PLA) is a biodegradable, Figure 1. Electrospinning Apparatus biocompatible material that can be modified using Electrospinning is applicable since the large copolymers to achieve specialized properties that can electrostatic field essentially phase separates be applied to the previously mentioned polymers with dissimilar polarizabilities and applications.[5] By adding a less hydrophobic hydrophobicity.[6, 9] When the two polymers are polymer to bulk PLA it is possible to modify the combined with a solvent and then through hydrophobic surface properties of PLA.[6-8] By the electrospinning the solvent is removed, the phase addition of PLA-b-PEG to bulk PLA this research separation can take place.[10-12] intends to determine the proper amount of PLA-b- PEG necessary to maximize migration of PEG to the By achieving this phase separation, the properties of electrospun fiber surface. the PEG can be exploited due to the hydroxyl end groups of PEG that can allow for covalent attachment Electrospinning is the process of applying an with other molecules.[13] In the future this would be electrostatic field by way of a high voltage to a useful for disease and contamination detection. grounded collector that creates nano to micro scaled fibers from a polymer solution.[2] The APPROACH electrospinning apparatus used in this study is shown The optimal PLA-b-PEG block lengths and block in Figure1. length ratios to maximize PEG at the fiber surface will be determined by spin-ability and use of wettability testing to measure increased water uptake as PEG is increased at the fiber surface. Varying chain lengths of di-block copolymer PLA-b-PEG will be investigated to achieve the optimum chain length necessary for greatest migration of PEG to the electrospun fiber surface. Time-of-flight Secondary Ion Mass Spectrometry (ToF-SIMS) is currently being done to quantify how much PEG is going to the surface of the fibers .

RESULTS AND DISCUSSION With the addition of PLA-b-PEG, fiber diameter 90 Tg PLA(1000)‐ decreases significantly when compared to that of the 80 control PLA fibers. This is believed to be the result of b‐PEG(5000)

70C) changing the viscosity, molecular weight, and surface ˚ Tg PLA(1000)‐b‐ 60 tension. After a point however, the addition of PLA- PEG(10000) b-PEG begins to result in larger diameter fibers as a 50 Tg PEG(6000) result of rheology. This was shown through SEM and 40 ImageJ™ analysis. 30 Tc PLA(1000)‐b‐ PEG(5000) 20Temperature( PLA(1000)-b-PEG(5000) proved to be the most 10 Tc PLA(1000)‐b‐ PEG(10000) efficient in phase separation of PEG to the fiber 0 surface as shown by the wettability results. Tc PEG(6000) 0 2 4 6 8 10 12 14 16 PLA(1000)-b-PEG(10000) showed an increase in PEG at the fiber surface, however it was not as Wt% PEG in Final Fiber significant as PLA(1000)-b-PEG(5000). This is Figure 3. Tg and Tc data for varying wt% of thought to be due to the long chain length of the copolymer/homopolymer. PEG(10000) entangling more when spinning than the shorter length PEG. Wettability results for CONCLUSIONS PLA(1000)-b-PEG(5000) show a plateau that PLA fibers are not hydrophilic, but with the addition emerges after 10wt% PEG as shown in Figure 2. of the block copolymers, the fibers began to show an PLA(1000)-b-PEG(10000) and PEG (6000) increase in hydrophilic nature. This is confirmed homoplymer are currently being investigated for this through wettability data. The DSC data begins to observance. show a decrease in Tc and Tg of the fibers with addition of PLA-PEG as well as to show the Tm of 8.0 PLA PEG after 12wt% PEG for the copolymers and at 5 wt% PEG 5wt% for the homopolymer. Based on the observance 10 wt% PEG of the Tm of PEG, it is confirmed that PEG was in- 6.0 fact making a contribution to the fibers properties. 12 wt% PEG With the results thus far, PLA(1000)-b-PEG(5000) is 14 wt% PEG 4.0 the best copolymer to be used to make a hydrophilic 16 wt% PEG yet not water soluble fiber.

2.0 FUTURE WORK Implementation of the optimal PLA/PLA-b-PEG fibers into micro fluidic devices for 0.0 disease/contamination detection is needed for the Figure 2. Wettability results for PLA(1000)-b-PEG(5000). future. By changing the fictionalization of the -OH on

the PEG different diseases and contaminations will DSC results showed that the glass transition be able to be investigated. temperatures and crystallization temperatures decreased with addition of the copolymer PLA-b- REFERENCES PEG as shown in Figure 3. This was determined to be 1. A.M. Rossi, L.W., V. Reipa, T.E. Murphy, Porous to the result of PEG plasticizing the sample, as shown Silicon Biosensor fo Detection of Viruses. Biosensors and by the bulk PLA spun with homopolymer PEG, Bioelectronics, 2007. 23: p. 741-745. whose Tg and Tc also decreased with increasing wt% 2. Q. P. Pham, A.G.M., Electrospinning of Polymeric PEG. DSC data also began to show the Tm of PEG at Nanofibers for Tissue Engineering Applications: A Review. loading greater than 12wt%. Tissue Engineering. Tissue Engineering, 2006. 12(5): p. 1197-1211. 3. Nadeau, J., Editorial: Nanotechnological Advances in Biosensors. Sensors, 2009. 9: p. 8907-8910. 4. Ping Lu, B.D., Applications of Electrospun Fibers. Recent Patents on Nanotechnology, 2008. 2: p. 169-182. 5. K. Madhavan Nampoothiri, N.R.N., Rojan Pappy John, An Overview of the Recent Developments in Polylactide (PLA) Research. Bioresource Technology, 2010. 101(22): p. 8493-8501. 6. Hendrick, E., in Fiber Science & Apparel Design. 2011, Cornell University: Ithaca. 7. É Kissa, I.B., E.I. Vargha-Butlerc, XPS and Wettability Characterization of Modified Poly(lactic acid) and Poly(lactic/glycolic acid) Films. Journal of Colloid and 11. M. Bognitzki, W.C., T. Frese,, M.H. A.Schaper, M. Interface Science, 2002. 245(1): p. 91-98. Steinhart,, and J.H.W. A.Greiner, Nanostructured Fibers 8. M. Zhang, X.H.L., Y.D. Gong, N.M. Zhao, X.F. Zhang, via Electrospinning. Advanced Materials, 2001. 13(1): p. Properties and Biocompatibility of Chitosan Films 70-72. Modified by Blending with PEG. Biomaterials, 2001. 23: p. 12. M. Bognitzki, T.F., M. Steinhart, A. Greiner, J. H 2641-2648. Wendorff, A. Schaper, M. Hellwig, Preparation of Fibers 9. Buyuktanir, E.A., M.W. Frey, and J.L. West, Self- With Nanoscaled Morphologies: Electrospinning of assembled, optically responsive nematic liquid Polymer Blends. Polymer Engineering and Science, 2001. crystal/polymer core-shell fibers: Formation and 41(6): p. 982-989. characterization. Polymer, 2010. 51(21): p. 4823-4830. 13. Harris, J.M., Polyetheylene Glycol- Biotechnology. 10. R. A. L. Jones, R.W.R., Polymers at Surfaces and 1992, New York: Plenum Press. Interfaces. 2006, Cambridge University Press: New York.

The Effects of Solvents on the Morphology and Conductivity in PEDOT:PSS/PVA Nanofibers Meryem Oznur Pehlivaner, Margaret Frey Department of Fiber Science and Apparel Design, Cornell University, Ithaca, NY 14853, United States [email protected]; [email protected]

STATEMENT OF PURPOSE good fiber morphology and many beads are observed. On The goal of this research is to investigate the solvent the other hand, the fiber morphology improves with effect on the morphology and conductivity in increasing percent of ethylene glycol. By adding DMSO PEDOT:PSS nanofibers. Conductive PEDOT:PSS to spinning dopes, there is an improvement in fiber nanofibers were obtained using PVA as the carrier morphology, however the best fibers resulted from through the electrospinning of aqueous dispersion of introducing EG to the dopes; less beady and the most PEDOT:PSS. uniform. 3µm 3µm 3µm INTRODUCTION Electrically conductive polymers simultaneously show the physical and chemical properties of organic polymers and the electrical properties of metals. PEDOT:PSS, a conducting polymer, has drawn much attention because of its superior conductivity, electrochemical as well as 3µm 3µm thermal stability. However, when compared with other conducting polymers, PEDOT:PSS shows lower conductivity, generally less than 1 S/cm. Recently, it has been shown that by incorporation of some organic solvents such as ethylene glycol, poly(ethylene Fig.1. SEM images of electrospun PEDOT:PSS/PVA glycol), dimethyl sulfoxide (DMSO), or sorbitol, in an fibers obtained from 4 wt. % PVA in PEDOT:PSS aqueous dispersion of PEDOT:PSS results in an aqueous dispersion with varying weight percentages of improvement of the conductivity of PEDOT:PSS thin EG and DMSO (a) (b) 2.5 wt.% EG, (c) 5 wt. % EG, (d) films[1‐8]. However, the precise mechanism by which is 2.5 wt.% DMSO (e) 5 wt. % DMSO. increased induces is somewhat a controversial issue. Electrical conductivity would improve conductivity through increased interaction Table I shows the room temperature conductivity of between the PEDOT chains. PEDOT:PSS/PVA fibers. After adding 5 wt.% EG and Although conductive PEDOT:PSS nanofibers have been DMSO to the spinning dopes, more conductive fibers reported recently[9,14,15], solvent effects on the production were obtained. The conductivity of fibers is increased up of these nanofibers, however, have not been studied to 30 folds of the original PEDOT:PSS fibers by adding 5 thoroughly. This study examines the effects of added wt. % EG. ethylene glycol (EG) and DMSO on the morphology and Table I. Room temperature conductivity of the the conductivity of PEDOT:PSS/PVA nanofibers. PEDOT:PSS/PVA fibers prepared from varying percentages of DMSO or EG. APPROACH Conductivity PEDOT:PSS/PVA spinning dopes were prepared with Samples (S/m) varying amounts of organic solvents. Firstly, organic PEDOT:PSS fibers (pristine) 2.0x10-4 solvent was added to the aqueous dispersion of PEDOT:PSS fibers treated with PEDOT:PSS and stirred by magnetic stirrer for 9 hours. 2.5 wt.% EG 3.7x10-4 Then, 4 wt.% PVA was dissolved in solution at 88°C PEDOT:PSS fibers treated with overnight to ensure complete dissolution and 0.5 wt.% 5 wt.% EG 6.5x10-3 nonionic surfactant Triton X-100 was added and stirred PEDOT:PSS fibers treated with for 2 minutes with vortex. The polymer solutions were 2.5 wt.% DMSO 3.3x10-4 spun at room temperature at driving voltages of 15 kV PEDOT:PSS fibers treated with with a feed rate of 0.54 ml/hour. The distance between 5 wt.% DMSO 3.5x10-3 spinneret and collector was 11 cm. Raman spectroscopy and molecular orientation To understand the mechanism for the conductivity RESULTS AND DISCUSSION enhancement, the fibers, both before and after EG or Fiber Morphology DMSO treatment, were studied by Raman spectroscopy. Fig. 1 shows the SEM image of PEDOT:PSS/PVA The Raman spectra of untreated and treated nanofibers which were electrospun with varying percent PEDOT:PSS/PVA fibers, and are shown in Figure 2. of organic solvents. When the solvent does not add the spinning dopes, PEDOT:PSS/PVA fibers do not show TGA Results The thermogravimetric curve consists of a two step weight loss. The first one is the vapor and ethylene glycol desorption before 200°C and the second one is the PVA degradation between 200-300 °C.

Fig.2. Raman spectra of electrospun PEDOT:PSS/PVA fibers obtained from 4 wt. % PVA in PEDOT:PSS Fig.4. TGA results of electrospun fibers. aqueous dispersion with varying weight percentages of CONCLUSIONS EG and DMSO (a) 0 wt. % (b) 5 wt. % EG, (c) 5 wt. % Preliminary experiments show that different solvents play DMSO. an important role on fiber morphology and conductivity. The most clear difference was observed for the strongest FUTURE WORK band between 1400 and 1500 cm-1 associated with the Solution properties such as solution conductivity and symmetric C =C stretching from the thiophene rings. α β viscosity will be measured. To understand the change in This shift has been also reported for EG-treated molecular conformation XRD patterns and degree of PEDOT:PSS films and wet-spun fibers [10‐12]. There are [13, 14] crystallinity will be studied. two proposed resonant structures for PEDOT . The REFERENCES benzoid structure includes two conjugated π-electrons on [1] J. Ouyang, Q. Xu, C. Chu, Y. Yang, G. Li, J. Shinar, , the Cα=Cβ bond and the quinoid structure does not include Polymer. 2004, 45, 25. any conjugated π-electrons on the Cα-Cβ bond. The [2] T. Wang, Y. Qi, J. Xu, X. Hu, P. Chen, , Appl. Surf. symmetrical Cα=Cβ stretching has been commented as a Sci. 2005, 250, 1-4. transformation of the benzoid structure to the quinoid [10‐12] [3] H. Yan, H. Okuzaki, , Synth. Met. 2009, 159, 21–22. structure . Untreated PEDOT:PSS/PVA fibers may [4] S. Ashizawa, R. Horikawa, H. Okuzaki, , Synth. Met. have both resonant structures, but after treatment with EG 2005, 153, 1–3. or DMSO, the benzoid structure is thought to transform [5] O. P. Dimitriev, D. A. Grinko, Y. V. Noskov, N. A. the quinoid resulting in a dominance of the quinoid Ogurtsov, A. A. Pud, , Synth. Met. 2009, 159, 21-22. structures in the linear or expanded coil formation. [6] G. Greczynski, T. Kugler, W. R. Salaneck, , Thin Benzoid is the favored structure in the coil formation, Solid Films. 1999, 354, 1–2. whereas is the quinoid structure is the favored structure in [7] S. K. M. Jönsson, J. Birgerson, X. Crispin, G. the linear or expanded coil conformation. Greczynski, W. Osikowicz, A. W. Denier van der Gon, AFM results W. R. Salaneck, M. Fahlman, , Synth. Met. 2003, 139, 1. The morphology of treated and untreated PEDOT:PSS [8] J. Y. Kim, J. H. Jung, D. E. Lee, J. Joo, , Synth. Met. films was studied with AFM. After EG and DMSO 2002, 126, 2–3. addition (the same amount in the spinning dopes), large [9] M. F. Kaitlin Schrote, , Macromolecules. 2012. domains appeared and the surface roughness of the films [10] J. Ouyang, C. W. Chu, F. C. Chen, Q. Xu, Y. Yang, , increased because of the conformational changes in the Advanced Functional Materials. 2005, 15, 2. PEDOT structure. [11] J. Ouyang, Q. Xu, C. W. Chu, Y. Yang, G. Li, J. Shinar, , Polymer. 2004, 45, 25. [12] R. Jalili, J. M. Razal, P. C. Innis, G. G. Wallace, , Advanced Functional Materials. 2011. [13] A. Dkhissi, F. Louwet, L. Groenendaal, D. Beljonne, R. Lazzaroni, J. L. Brédas, , Chemical Physics Letters. 2002, 359, 5–6. [14] S. Garreau, G. Louarn, J. Buisson, G. Froyer, S.

Fig.3. AFM images of electrospun PEDOT:PSS films Lefrant, , Macromolecules. 1999, 32, 20. (a)pristine films (b) EG treated films (c) DMSO treated films.

Chitosan Fiber Scaffolds for Craniofacial Bone Tissue Engineering

Laura J. Toth1, Marjorie A. Kiechel1, Amalie E. Donius,2 Ulrike G.K. Wegst2 Caroline L. Schauer1 1Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 2Thayer School of Engineering, Dartmouth College, Hanover, NH [email protected], [email protected]

STATEMENT OF PURPOSE one-step crosslinked electrospun chitosan fibers This research highlights osteoblast interaction and growth mineralized with HAP. Osteoblast cells were grown on on novel mineralized and non-mineralized crosslinked the electrospun mats and characterized in order to electrospun chitosan (CS) fibrous mats to assess their determine the effect of crosslinker and mineralization on potential as bone scaffolds. cell growth and development.

INTRODUCTION APPROACH Craniofacial defects resulting from either trauma or Electrospun CS mats were prepared according to methods congenital conditions can severely impact patient quality developed by Austero et al., 2012.6 Briefly, 70% of life, from both an aesthetic and functional viewpoint. deacetylated chitosan was dissolved in trifluoroacetic acid Diseases such as Treacher-Collins syndrome and (TFA) and crosslinked with either genipin (gen) or hemifacial microsomia create a severe deformation of the hexamethylene-1,6-diaminocarboxysulphonate (HDACS) lower skull.1 Currently, tissue engineering techniques via a one-step method. Fiber mats crosslinked with have been explored for craniofacial bone reconstruction HDACS were post treated at 120oC, 2 h to activate the as an alternative to autologous or alloplastic bone crosslinking process. Preparation of the mineralized fiber substitutes.2 Autologous bone transplants, which utilize mats involved doping the CS solution with either 1 wt% bone cells extracted and expanded from the patient’s ribs or 10 wt% HAP. All CS solutions were electrospun with or skull, can lead to successful facial reconstruction.1 an applied voltage of 15 kV, at a collection distance of 10 However, unexpected complications can arise which cm and a flow rate of 1.0 mL/hr. include infection at the implant site, inadequate bone The preosteocyte line MLO-A5 utilized in this study was availability, and donor site morbidity. Because many of cultured per standard mammalian tissue culture protocol. those affected by craniofacial malignancies are children, Three different cell characterization methods were used to synthetic bone cements and/or constructs are abandoned define the osteoblast response to the electrospun CS fiber because of their failure to grow and develop.2 In addition, mats. These included immunofluorescent confocal these alloplastic materials often are not biodegradable or microscopy (IFC) and scanning electron microscopy bioresorbable, and can prevent integration with the (SEM) for cellular visualization, an adenosine surrounding bone.1 One very successful advancement in triphosphate (ATP) assay utilized to assess cell viability, craniofacial reconstruction involves the use of and real time reverse transcriptase polymerase chain demineralized bone matrix, which is derived from either reaction (RT-PCR) to measure pertinent bone analytes autologous or allogeneic bone. While this material has secreted during bone remodeling, growth, and shown to induce bone regeneration and growth, it can still development. Fiber diameters and mechanical properties promote infection and integration problems.1 Therefore, of the electrospun mats were assessed in order to there is a need for an implantable, biocompatible bone investigate their effect on cell growth. MLO-A5 cells scaffold created with biological materials that will support were also grown on polymer films of the same fiber bone growth and surrounding tissue integration, while solution compositions in order to better characterize the maintaining the mechanical integrity of natural osteoblast response to the fiber scaffolds. craniofacial bone. Electrospinning is a well-established, low-cost, polymer RESULTS AND DISCUSSION processing technique which results in non-woven nanoscale fibrous scaffolds with better surface area to (a)CS-gen (b)CS-HD120 (c)CS-gen 1HAP volume ratios compared to other fiber processes or tissue scaffolding techniques.3 The size of electrospun fibers impacts cellular adhesion and migration within the scaffold.4 Supporting cell diffusion is critical to scaffold integration with the surrounding tissue. Natural polymers (d)CS-gen 10HAP (e)CS-HD 1HAP (f)CS-HD 10HAP such as chitosan (CS) and collagen, as well as mineral additives including hydroxyapatite (HAP), have been investigated as materials for use in electrospun bone scaffolds. The first reported electrospun CS-HAP fibrous scaffold used a two-step method in which the respective FIGURE 1. SEM micrographs of the various CS fiber mat morphologies materials were co-precipitated, and then doped with PEO Both non-mineralized (a,b) and mineralized (c-f) fibers were prepared to facilitate electrospun fibers.5 Here we present novel with the indicated crosslinker. beneficial because during bone repair and regeneration, osteoblasts will create oriented collagen fibrils in parallel a b conformations. This lamellar bone structure is indicative of mature, healthy bone tissue.7 Results from the ATP viability assay reveal higher luminescence recorded with cells grown on CS-HDACS 120 fibers, as compared to CS-gen. Additional data suggest a marked difference in MLO-A5 response to the various CS scaffolds. c d CONCLUSIONS Electrospun CS fibrous scaffolds were successfully fabricated and crosslinked. Mineralized CS fibrous mats were prepared utilizing a one-step method. MLO-A5 cells, which are a preosteocyte lineage, demonstrated e f growth and proliferation upon all scaffolds tested. However, there appeared to be marked differences in cellular growth and attachment depending upon the type of crosslinker present and whether the fibrous scaffolds were mineralized. This work demonstrates the potential of an electrospun CS scaffold for craniofacial reconstruction and regeneration.

FUTURE WORK Future research involves further characterization of the interaction between the MLO-A5 cells and CS fibrous scaffolds. In addition, animal studies are envisioned to demonstrate the in vivo capabilities of the CS fibrous scaffolds.

KEYWORDS chitosan, bone tissue engineering, electrospinning

ACKNOWLEDGMENT FIGURE 2. Immunoflouresecent micrographs and ATP assay of cells The authors would like to thank the Bonewald Laboratory grown on various scaffolds . IFC micrographs (top) of MLO-A5 cells (University of Missouri-Kansas City) for the cell line and grown on non-mineralized CS fiber mats. The immunofluorescent NSF DMR 0907572 for funding this work. labels include DAPI (blue), which stains the cellular nucleus and phalloidin (green), which highlights the actin cytoskeleton. Glass coverslip only (a-b) CS-gen film (c) CS-gen fibers (d) CS-HDACS 120 REFERENCES film (e) CS-HDACS 120 fibers (f). Results of the ATP assay (bottom). 1. Nacamuli RP, Longaker MT. Orthodontics & Error bars represent SEM of 3 trials (TCP-tissue culture polystyrene). Craniofacial Research. 2005;8(4):259-266. 2. Turner CG, Klein JD, Gray FL, Ahmed A, Representative results from this study are featured in Zurakowski D, Fauza DO. Journal of Surgical Figures 1-2. Figure 1 displays the typical CS fiber Research. Online 21 May 2012. morphology of both the non-mineralized and mineralized 3. Lee CH, Shin HJ, Cho IH, et al. Biomaterials. electrospun mats. Figure 2 (top) reveals morphology 2005;26(11):1261-1270. indicative of healthy MLO-A5 cells grown on the non- 4. Hsu Y-M, Chen C-N, Chiu J-J, Chang S-H, mineralized crosslinked CS fiber mats. Results from the Wang Y-J. Journal of Biomedical Materials luminescent ATP assay show that MLO-A5 cells survive Research Part B: Applied Biomaterials. and proliferate while on the non-mineralized CS fiber 2009;91B(2):737-745. mats. 5. Zhang Y, Venugopal JR, El-Turki A, Comparison of additional results, including the SEM Ramakrishna S, Su B, Lim CT.. Biomaterials. micrographs and RT-PCR bone analyte concentrations, 2008;29(32):4314-4322. for both the non-mineralized and mineralized fiber mats 6. Austero MS, Donius AE, Wegst UGK, Schauer suggest that MLO-A5 cells respond differently depending CL. Journal of The Royal Society upon the crosslinker used within the CS fibers and Interface.201;.9.2551-2562. presence of HAP. Cells grown on non-mineralized CS- 7. Shapiro F. European cells & materials. HDACS 120 fiber scaffolds appear to orient themselves in 2008;15:53-76. horizontal and vertical layers, parallel to each other within this scaffold (Figure 2f). This orientation may be very

Preparation and Characterization of Organosilicate-Reinforced Electrospun Membrane

Fuan He, YuenShing Wu, Jintu Fan Department of Fiber Science and Apparel Design, College of Human Ecology, Cornell University, Ithaca, New York 14853 [email protected]

INTRODUCTION P(VDF–TrFE)/organosilicate nanofibers by Electrospinning is an effective technique to prepare electrospinning. flexible nanofibrous membranes. Recently, the electrospun piezoelectric membranes based on fluoro polymer have attracted much attention because they are potential materials in many areas including power nanogenerator, sensor, tissue engineering, filtration membrane, and polymer electrolyte. However, the poor mechanical performance of such electrospun membranes greatly limits their practical application. Currently, it is still a challenge to prepare an electrospun piezoelectric Figure1 SEM images of P(VDF–TrFE) nanofibers and membrane with good mechanical properties. P(VDF–TrFE)/organosilicate nanofibers.

Organically modified layered silicate is an excellent The electrospun P(VDF-TrFE) membrane has very low nanoscale reinforcing agent which has good compatibility tensile strength and modulus of 6.0 and 1.32 MPa with a with hydrophobic polymer. When organosilicates are elongation at break of 55.0%. In contrast, the values of dispersed well in the fluoro polymer matrix, the resultant tensile strength, modulus, and elongation at break for nanocomposites can exhibit remarkable improvement in POS10 are 12.9 MPa, 26.8 MPa, and 89.6%, respectively. mechanical properties. Herein, we report a novel It means that the addition of organosilicates into P(VDF- electrospun membrane based on poly(vinylidene- TrFE) nanofibers can effectively improve the mechanical trifluoroethylene) [P(VDF–TrFE)] and organosilicate (10 performance of result electrospun membranes. wt%), which demonstrated remarkable improvements in strength, stiff, ductile when compared to those of pure The compressive piezoelectric response of electrospun electrospun P(VDF–TrFE) membrane. It is also worth membranes is shown in Figure 2. It can be seen that the noting that the electrospun P(VDF–TrFE)/ organosilicate piezoelectricity of electrospun P(VDF- membrane possesses other advantages such as the high TrFE)/organosilicate membranes still remains although its porosity and piezoelectricity. voltage output is about 40% lower than that of electrospun P(VDF-TrFE) membrane. APPROACH For the preparation of electrospun P(VDF-TrFE)/ organosilicate membrane (POS10), OMLS was added into a DMF-acetone solvent. Next, the P(VDF-TrFE) copolymer was dispersed in the OMLS suspension by magnetic stirring at 50 oC for 3 hours. The P(VDF- TrFE)/organosilicate solution was then ultrasonicated at room temperature for another 1 hour. The resultant P(VDF-TrFE)/organosilicate solution were put into a plastic syringe. A DC voltage was applied to the needle tip of syringe to electrospin P(VDF-TrFE)/ organosilicate naofibers on a rotating drum collector.

A JSM-6490 scanning electron microscope (SEM) was employed to observe the nanofiber morphology of Figure2 The compressive piezoelectric response of electrospun membranes. Tensile testing was carried out electrospun membranes. by using an Instron 5566 machine. Piezoelectric testing was conducted on a self-made equipment. CONCLUSIONS Electrospun nanofibrous P(VDF-TrFE)/organosilicate RESULTS AND DISCUSSION membrane has been prepared successfully in this work. As shown in Figure 1, the SEM images confirm the We believe that such an organosilicate-reinforced durable successful formation of P(VDF–TrFE) nanofibers and porous P(VDF–TrFE) membrane will be a promising material not only in e-textile application but also in other REFERENCES areas (e.g. filter membrane, tissue engineering, polymer [1] J. Fang, X.G. Wang, T. Lin, J. Mater. Chem. 2011, 21, electrolyte) under harsh condition without damage. 11088-11091. [2] Y. R. Wang, J. M. Zheng, G.Y. Ren, P.H. Zhang, C. KEYWORDS Xu, Smart. Mater. Struc. 2011, 20, 045009. poly(vinylidene-trifluoroethylene), organosilicate, [3] D. Dhakras, V. Borkar, S. Ogale, J. Jog, Nanoscale. electrospinning, improved mechanical performance, 2012, 4, 752-756. piezoelectricity [4] D. Mandal, S. Yoon, K.J. Kim, Nanoscale. 2011, 4, 831-837. ACKNOWLEDGMENT The authors would like to acknowledge the funding support of the Postdoctoral Fellowship of Hong Kong Polytechnic University (Project No: G-YX1K).

Incorporation and Performance of Molecular Polyoxometalates in Cellulose Substrates

Nancy Elizabeth Allen, S. Kay Obendorf Department of Fiber Science & Apparel Design, Cornell University [email protected]

STATEMENT OF PURPOSE Oxygen or any oxidant in the system can then re- In this study, high surface area, microporous, oxidize the POM to its original state [4]. nanofibrous cellulose acetate membranes are functionalized with catalytic molecular polyoxometalates (POMs) in order to examine their self-decontamination performance. The POMs are grafted to traditional microporous nanofibrous electrospun cellulose acetate membranes as well as super high surface area, channeled, cellulose acetate Figure 1: Structure of an α-Keggin type polyoxometalate [3], [2] nanofibers. It is hypothesized that by using the channeled cellulose acetate nanofibers, the surface area of traditional microporous, nanofibrous, cellulose acetate membranes is increased providing more active sites to which the POMs will bind. This increase in POM active sites enhances the catalytic degradation Figure 2: Catalytic cycle of polyoxometalate nanoparticles [4] performance of methyl parathion, an organophosphate POMs have been incorporated into fibers and fabrics simulant of the chemical warfare agent (CWA) VX. such as polyacrylic, nylon, cotton, and polyurethane The overall objective of this work is to incorporate sponges in order to examine their catalytic self- high loads of self-decontaminating compounds in decontamination of volatile organics, air toxins, and semi-permeable, breathable, textile substrates and chemical warfare agents. POMs grafted to cotton characterize their self-decontaminating performance in and other cellulosic substrates have been examined order to reduce the penetration of CWAs and maintain for breathable protective performance apparel [5], thermal comfort in personal protective apparel for [6], [7]. defense personnel. POMs such as H5PV2Mo10O40 have been prepared by INTRODUCTION Dr. Craig Hill of Emory University and can be Polyoxometalates are heteropolyanions, otherwise incorporated into micro- or nano- electrospun fibers known as polymeric oxoanions, formed by the and film coatings for fabrics [8]. 10-Molybdo-2- condensation of more than two different oxoanions. vanadophosphoric acid has been incorporated into These negatively charged nanoclusters of oxide and cellulose substrates to degrade volatile organics and transition metal ions in their highest oxidation state chemical warfare agents such as CEES [5], [6], [9]. 4+ have the general formula of XM12O40 . X can be Si 5+ or P etc, and M can be tungsten, molybdenum, The current approach to achieving enhanced methyl vanadium and other metals. In their free acid form parathion degradation with POMs in channeled polyoxometalates are referred to as heteropoly or cellulose acetate nanofibers entails the fabrication of isopoly acids. POM free acids and their salts act as the high surface area cellulose acetate membrane, its strong acids and have been widely used as acid characterization, POM synthesis, the grafting of catalysts and oxidation catalysts that yield better POMs to the cellulose membrane, and the oxidation performance than hydrogen peroxide, characterization of the POM functionalized ozone, and molecular oxygen when environmental membranes. profiles and efficiency of oxidation are taken into account [1]. The majority of polyanions with APPROACH tetrahedrally-coordinated heteroatoms have structures Fabrication & Characterization of High Surface based on what is known as the Keggin anion [2]. Area Cellulose Acetate Membranes H5PV2Mo10O40 is a heteropolymolybdovanadate free Cellulose acetate / polyethylene oxide nanofibers are acid and is classified as an α-Keggin structure. Figure electrospun and then extracted with deionized water 1 illustrates what is known as an α-Keggin type using a soxhlet extraction setup. The extraction polyoxometalate [3]. Figure 2 illustrates the rapid, removes the polyethylene oxide from the fibers to reversible redox changes that classify these form grooved or channeled nanofibers. The nanoparticles as catalytic and self-regenerating. When nanofiber membranes are then vacuum dried. FTIR the oxidation reaction occurs, the POM is reduced. analysis is performed in order to confirm the removal of the polyethylene oxide and the presence of cellulose acetate. A scanning electron microscope 100% unbleached cotton swatches. Experiments are (SEM) is used to confirm the grooved fiber underway to investigate the cause of this morphology [10], [11]. phenomenon.

The pore size, pore size distribution, fiber size, fiber FUTURE WORK morphology, and surface area of these membranes is Further investigation of the decontamination measured using a porometer, a scanning electron performance of the non-grooved cellulose acetate microscope (SEM), and a gas adsorption technique nanofibrous membranes is underway. Also, the known as BET. The measurement of additional degradation products of the decontamination mechanical and thermal properties also helps to experiments are being examined using ion characterize the strength and composition of the chromatography. The surface area of the 100% membranes [11]. cotton swatch must be determined in order to explain the higher degradation performance. These electrospun regenerated cellulose nanofiber membranes can be loaded with the self- ACKNOWLEDGMENT decontaminating POM H5PV2Mo10O40 via a grafting This research is funded by the Department of Fiber process. In this process a reactive oxygen species is Science and Apparel Design at Cornell University. created by reacting the hydroxyl groups on the Great thanks are extended to Dr. S. Kay Obendorf, surface of the cellulose with a diisocyanate, which Laurie Lange, and Dong Jin Woo of Cornell thus provides a grafting site for H5PV2Mo10O40 . The University for their help and efforts in the reaction is performed under a nitrogen purge in the development of this project. presence of a tin (II) catalyst, and a toluene solvent [12]. The membranes are then submerged in a REFERENCES hexane solvent containing methyl parathion for [1] Misono, M., “Heterogeneous catalysis by heteropoly compounds of molybdenum and tungsten,” Catalysis Reviews Science and designated time intervals. The catalytic degradation Engineering, 29(2-3), 1987, 269-321. of the methyl parathion is determined via liquid [2] Pope, M. T., “Heteropoly and isopoly oxometalates,” Berlin: chromatography and mass spectroscopy (LCMS). The Springer-Verlag, 1983. [3] Johnson, R. P., & Hill, C. L., “Polyoxometalate oxidation of decontamination performance of the membranes is chemical warfare agent simulants in fluorinated media,” Journal of compared to the decontamination performance of Applied Toxicology : Jat, 19, January 01, 1999, 71-5. 100% non-bleached cotton swatches that are grafted [4] Ozer, R. R., and Ferry, J. L., “Kinetic probes of the mechanism of polyoxometalate-mediated photocatalytic oxidation of chlorinated with POM particles using the same process described organics,” Journal of Physical Chemistry B, 104(40), 2000, 9444- above. 9448. [5] Xu, L., Boring, E., & Hill, C., “Polyoxometalate-Modified Fabrics: New Catalytic Materials for Low-Temperature Aerobic Polyoxometalate Synthesis Oxidation,” Journal of Catalysis, 195, 2, January 01, 2000, 394-405. 10-Molybdo-2-vanadophosphoric acid [6] Drechsler, U., Singh, W. and Sharma, A., (2009). U.S. Patent Application No. 2009/0012204 A1. Washington, DC: U.S. Patent and (H5PV2Mo10O40) is synthesized via a reaction of Trademark Office. sodium metavanadate (NaVO3) with disodium [7] Walker, J., Schreuder-Gibson, H., Yeomans, W., Ball, D., Hoskin, phosphate (Na2HP04) and the resulting compound’s F., and Hill, C., ARMY NATICK SOLDIER CENTER MA., reaction with concentrated sulfuric acid and sodium “Development of self-detoxifying materials for chemical protective clothing,” Ft. Belvoir: Defense Technical Information Center, 2003. molybdate (Na2MoO4) in methanol. The acid is [8] Gall, R., Hill, C., & Walker, J., “Selective Oxidation of Thioether purified to obtain the correct stoichiometry. After Mustard (HD) Analogs by tert-Butylhydroperoxide Catalyzed by H extraction, the resulting compound is a reddish orange 5PV 2Mo 10O 40 Supported on Porous Carbon Materials,”Journal of Catalysis, 159, 2, April 01, 1996, 473. crystal [13]. [9] Hill, C., Xu, L., Rhule, J. T., Boring, E., (2001). World Intellectual Property Organization No. WO 01/34279 A2, WPO Patent and RESULTS AND DISCUSSION Trademark Office. [10] Liu, H., & Hsieh, Y.-L.,“Ultrafine Fibrous Cellulose Membranes Experiments are currently underway, and additional from Electrospinning of Cellulose Acetate,” Journal of Polymer results will be forthcoming. The use of the grooved Science. Part B, Polymer Physics, 40, 18, January 01, 2002, 2119. microporous cellulose acetate nanofiber membranes [11] Dixit, V., Tewari, J., & Obendorf, S. K.., “Fungal growth inhibition of regenerated cellulose nanofibrous membranes containing lead to an increase in the fiber surface area compared quillaja saponin,” Archives of Environmental Contamination and to non-channeled nanofibrous cellulose acetate Toxicology, 59, 3, October 01, 2010, 417-423. membranes. The increased surface area produces [12] Tan, K., & Obendorf, S. K.., “Surface modification of microporous polyurethane membrane with poly(ethylene glycol) to more active sites to which H5PV2Mo10O40 binds. develop a novel membrane,”.Journal of Membrane Science, 274, 1, More active sites for the molecular POM binding January 01, 2006, 150. increases the catalytic degradation of methyl [13] Tsigdinos, G. A., & Hallada, C. J., “Molybdovanadophosphoric acids and their salts: I. Investigation of methods of preparation and parathion. The nanofibrous membranes did not characterization,” Inorganic Chemistry, 7, 3, March 01, 1968, 437- outperform the decontamination performance of the 441. Nanoconfinement-Induced Enhancement of Thermal Energy Transport Efficiency in Electrospun Polymer Nanofibers

Zhenxin Zhong1, Matthew C. Wingert3, Joe Strzalka1, Tao Sun1, Hsien-Hau Wang2, Jin Wang1, Renkun Chen3, Zhang Jiang1 1X-ray Science Division, 2Material Science Division, Argonne National Laboratory, Argonne IL 60439, 3Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093 [email protected]

ABSTRACT polymer nanofibers. A detailed and quantitative Polymers (e.g., polyethylene) that are usually good understanding of the nano-structure evolution in the thermal insulators in bulk forms were found to be good interior of the nanoscale fibers with different diameters thermal conductors when they are drawn into one- and post-spinning processing histories was revealed by in- dimensional fibers with high draw ratios and nanoscale situ synchrotron x-ray scattering. diameters [1]. The internal structures (such as the crystalline domains), chain entanglements, and defects Thermal properties of individual suspended nanofibers morphologies are believed to affect the phonon were measured on a micro-scale Wheatstone differential propagation that is directly related to a polymer’s thermal bridge circuit, which provides an ultra-high sensitivity of energy transport properties. However, no systematic and the conductance (~0.1 nW/K) [2]. A thermal conductivity quantitative understanding of this structure-function increase of approximately five times in compared to thick relationship exists to date. Understanding the correlation fibers and bulk Nylon samples was achieved in as-spun between the structure and properties under real conditions Nylon-11 fibers of diameters of ~100 nm. Post-spinning during the growth and fabrication of the polymer hot stretching was found to further increase the nanofibers is crucial to the design and fabrication of conductivity. This enhancement has been correlated with polymer nanofibers that meet the need for an efficient the change of the internal crystalline structures and thermal energy transfer that requires high thermal domain orientations in the nanofibers. conductivity as well as electrical insulation, high chemical stability, lightweight, high mechanical performance, and KEYWORDS low-cost mass-production. Thermal conductivity, polymer nanofiber, x-ray diffraction, thermal conductivity Electrospinning is a simple and versatile method to produce one-dimensional nanofibers with controlled fiber ACKNOWLEDGMENT diameters, morphology, and internal structures. The Work at Argonne and use of the Advanced Photon Source performance of nanofiber-based devices strongly depends is supported by Laboratory Directed Research and on the structure and properties of individual polymer Development (LDRD) funding and US Department of nanofibers. In this study, the structure, morphology, and Energy Office of Science under Contract No. DE-AC02- orientation development in electrospun nanofibers, 06CH11357. Work at UCSD is supported by UCSD including nylon, polyvinylidene fluoride, and polymer research start-up funds and Hellman Faculty award. ethylene nanofibers, were investigated by synchrotron x- ray diffraction, scanning electron microscopy, and REFERENCES transmission electron microscopy. A unidirectional [1] S. Shen, et al., Nat. Nanotech. 5, 251 (2010). stretching and annealing device was developed to [2] M. C. Wingert, et al., Nano Lett., 11, 5507 (2011). improve the crystal structure and orientation of as spun

Reactivity of Methyl Parathion Degradation with Immobilized Zinc Oxide Nanoparticles

Yunfei Han, S. Kay Obendorf Cornell University [email protected]

INTRODUCTION immobilize ZnO nanoparticles. Electrospinning was used Chemical or biological warfare (CBW) agents have to make celullose/ZnO nanofibers. threatened U.S. military and normal people’s lives. Protection gear and apparel are urgently needed for both OBJECTIVES the military and professional workers. In recent years, U.S. There are three objectives for this research. The first Government has put intensive efforts to protect military objective is to confirm the necessity of UV in methyl and residents from CB agents. Although researchers parathion’s self-decontamination by ZnO. The second found several ways to remove hazardous CBW agents objection is to understand the degradation product and [1,2], they have different problems when used in military degradation activity of methyl parathion by immobilized apparel. Since military apparel requires properties of ZnO nanoparticles. The third objective is to investigate breathability, durability, washability as well as self- changing of detoxification activity of immobilized ZnO detoxification ability, many of these methods are not during several reusing cycles. suitable. APPROACH Methyl parathion, a CBW agent and a widely used Effect of UV pesticide, was used as the model chemical toxin in this Experiment is done with and without UV to see if UV is research. Methyl parathion is a toxic organophosphate, necessary in ZnO decontamination. [6] Samples and it is classified by World Health Organization (WHO) containing define amount of ZnO nanoparticles are as an extremely hazardous (Class IA) toxicity. reacted for one of two times (20, 60min) in visual light and UV light. After the reaction, the hexane solution is filtered run on the HPLC-MS. Instrument drift of the HPLC-MS is normalized with the use of methyl parathion standard and calibration curves. Fig. 1: Chemical structure of methyl parathion Fiber Formation TiO2 and ZnO, both are photocatalysts, have been proven Electrospun cellulose/ZnO nanofibers are made for to degrade methyl parathion [3]. The degradation of further experiments. ZnO nanoparticles are mixed with a methyl parathion using TiO2 photocatalysis has been define solution of cellulose acetate in acetone solvent, previously investigated [4]. However, no significant effort then electrospinned CA/ZnO nanofiber. CA nanofibers has been made in evaluating the photocatalytic efficiency without ZnO were also made as a control to prove it is of ZnO on methyl parathion degradation. This research ZnO rather than the cellulose fibers degraded methyl focused on methyl parathion degradation with presence of parathion. Then, CA nanofibers are deacetylated by ZnO as the photocatalyst. NaOH/ethanol solution to obtain cellulose (RC) nanofibers. [8] FT-IR are used to confirm the total Other than photocatalystic degradation, destructive deacetylation and SEM was used to see the fiber adsorption might take place during methyl parathion formation of CA/ZnO nanofibers. decontamination by ZnO. [5,6] Destructive adsorption don’t need UV light as condition. In order to confirm the Reactivity of Methyl Parathion Degradation with necessity of UV in methyl parathion’s self- RC/ZnO Nanofibers decontamination by ZnO, experiment in two different Samples containing RC/ZnO nanofibers are reacted with environment conditions was done: UV light and visual define amount of methyl parathion in hexane with the light. present of UV. The expected degradation products are methyl paraoxon, O,O,O-trimethyl phosphoric thiourate, Incorporation of the ZnO nanoparticles into fibers or and p-nitrophenol[7]. fabrics is a way to create a self-decontaminating textile without loss of garment comfort. It is also a good way to To compare the degradation products found in the hexane FUTURE WORK and aqueous solutions, HPLC-MS is used. The hexane Reusing Property of ZnO solution is filtered and then run on the HPLC-MS. The To produce better protection apparel, it is expected to be nanofibers are then rinsed and dried. Same amount of washable and reusable. To remove degradation product water is added in RC/ZnO nanofibers and all the water- retained on ZnO surface, water was used to extract any soluble compounds on the surface of those RC/ZnO water-soluble compounds from ZnO nanoparticles surface nanofibers surface and then run on the HPLC-MS. [6]. During several wearing cycle and wash cycle, self- Instrument drift of the HPLC-MS is normalized with the decontamination property should not be lost on protection use of methyl parathion, methyl paraoxon and 4- garment. Therefore, in this research, self-decontamination nitrophenol standards and calibration curves. activity on methyl parathion will be tested after each wash cycle to see whether the self-decontamination activity RESULT AND DISCUSSION decreases or how it decreases.

4750 Degradation Activity of ZnO Nanorods Fabrics Reaction activity of ZnO Nanorods on cotton fabrics will 4700 be tested. It’s provided by Dr. Ruya Ozer provdes from 4650 University of Tulsa.

4600 20min ACKNOWLEDGMENT 4550 without UV 60min This research is funded by the Department of Fiber 4500 without UV Science and Apparel Design at Cornell University. 20min UV Great thanks are extended to Dr. S. Kay Obendorf, 4450 60min UV Laurie Lange, and Nancy Elizabeth Allen of Cornell 4400 University for their help and efforts in the 20min 60min 20min 60min development of this project. without without UV UV UV UV REFERENCES

Fig. 2 Methyl Parathion HP-LC area under different [1] Yang, Y., “Decontamination of Chemical Warfare conditions Agents” Chem. Rev., 1992, 92, 1729-1743. [2] Herrmann, H. W., “Chemical Warfare Agent Decontamination Studies in the Plasma Decon Chamber” 0.35 IEEE Transactions on Plasma Science, 2002, 30, 4. 0.30 [3] Evgenidou, E., “Photocatalytic oxidation of methyl 0.25 parathion over TiO2 and ZnO suspensions” Catalysis Today, 2007, 124, 156-162. 0.20 [4] Chen, T., “Photocatalytic degradation of parathion in 0.15 aqueous TiO2 dispersion: the effect of hydrogen peroxide 0.10 and light intensity” Water Sci. Technol., 1998, 37, 187. 0.05 [5] Volodin, A., “Nanoscale oxides as destructive sorbents for halogenated hydrocarbons” Surface Absorbance 0.00 Chemistry in Biomedical and Environmental Science, ‐0.05 2006, Part 3, 403-412. 4,000.00 3,000.00 2,000.00 1,000.00 0.00 [6] Lange, L., “Effect of plasma etching on destructive Wavenumber (cm‐1) adsorption properties of polypropylene fibers containing magnesium oxide nanoparticles” Arch Environ Contam Toxicol , 2012, 62 (2), 185-95. Fig. 3. FTIR spectra for nanofiber before and after [7] Senthilnathan, J., “Removal of mixed pesticides from deacetylation. Solid line: After deacetylation; Dash line: drinking water system by photodegradation using Before deacetylation suspended and immobilized TiO2” Journal of Environmental Science and Health, 2009, Part B 44: 262- Experiments are currently underway, and more results 270. will be forthcoming. Expected out comes include the UV [8] Liu, H., “Ultrafine fibrous cellulose membranes from is a necessary part of the reaction, methyl parathion can electrospinning of cellulose acetate” Journal of Polymer be degraded by RC/ZnO nanofibers. More information Science, 2002, Part B 40 (18), 2119-2129. will be presented.

Surface Electromyography Using Textile-Based Electrodes

André Catarino1, Helder Carvalho1, Luis Barros2, Maria Dias2 1Textile Engineering Department, University of Minho, Portugal 2 Centre for Textile Science and Technology, University of Minho, Portugal [email protected]; [email protected]

ABSTRACT steel fibers and multifilament yarns, instead of silver. The Surface Electromyography (sEMG) is a fundamental problem of stabilization in place is generally tackled by method for study the biomechanical behavior of a person, means of using compression garments, instead of allowing the extraction of valuable information for health adhesives. professionals. This paper presents a research conducted with the purpose of developing textile electrodes for non ELECTRODE FABRICATION invasive surface electromyography. Conducting fibers There are some technologies available for producing the were used in a specifc arrangement taking into structure that will form the electrode. Weft knitting was consideration SENIAM recommendations and embedded selected, since it presents some advantages, such as only in a textile fabric. A comparison was made between one conductive yarn is enough to build the electrode. It conventional electrodes and the proposed ones. The was decided to use a seamless knitting machine, since it is results showed that the behavior is similar, which can specially designed to produce body wear garments. constitute a valid alternative, overcoming some Another important feature is the fact that these machines disadvantages such as the comfort for the user. are full jacquard, which allows placing the electrode in any location and with the shape and structure desired. In KEYWORDS: surface electromyography, textile order to obtain compression, the fabrics with embedded electrodes electrodes were produced also with bare elastane together with the base yarn polyamide. INTRODUCTION Not all conductive yarns are adequate for knitting. The There are two possible approaches for measuring the mechanical properties play an important role, since the muscular activity through electromyography (EMG): operations involved during knitting will make the yam to invasive and non invasive. While the former basically use bend, suffer significant stress, among other effects. The intramuscular needles which allow to measure internal yarn may be so strong and abrasive that will destroy the muscles and identify a smaller number of motor units base yarn and the elastane. From the conductive yarns (muscular cell), the latter is applied on top of the muscle, available, the team selected two yarns: a blend made of in direct contact with skin, thus allowing to measure 80% polyester and 20% stainless steel, also known as muscles that are at the surface and grouping in the Bekitex BK, and identified as yarn FA; a multifilament resulting signal several motor units. Regarding the non yarn made with 80% of silver-covered polyamide and invasive approach, conventional electrodes are available 20% elastane, known as Elitex, identified in the in rigid and non rigid forms, and are attached directly on experiments as yarn FB. Several structures were made top of the muscle that is intended to be monitored. The based on knit, tuck and float variations with the purpose attachment generally made using adhesive tape or similar. of identifying which was the one that provides a stronger With the purpose of improving the user’s comfort, the signal. From those experiments one found that a research team proposed in previous works [1,2] to combination of float and knit loops provide a structure develop textile electrodes embedded in the fabric, easy to more reliable in terms of signal strength and reliability. wear and getting similar results to conventional Figure 1 illustrates a version of those electrodes. These electrodes. There are several studies made regarding specific electrodes have the dimension of 3.5x4.0 cm (A) textile based electrodes, mainly for ECG applications, as and 3.8x4.3 cm (B). it is mentioned by [3]. The technologies generally used involve weft knitting [1-4], woven fabrics and embroidery applications [5]. The use of textile electrodes rise questions like the skin-electrode impedance since they are heterogeneous and form a very complex structure in terms of electrical impedance associations. There are textile structures that present better results than others. Concerning sEMG, the capacitive principle is presented Figure 1. Textile electrodes with FA yarn (left) – by [5], while [4] prefer the traditional method of direct electrode A; and FB yarn (right) – electrode B. contact with skin. Since the electrodes are textile structures, the raw material In order to compare the textile with conventional is also matter of concern and study, as mentioned by [1, electrodes, used in sEMG, a version of textile electrodes 6]. Not all the conductive materials may be the most was produced taking into consideration SENIAM adequate, as stated in [6,7], suggesting the use of stainless recommendations. These electrodes, illustrated in Figure 2, present the dimensions of 4.0 cm length and 0.5 and 0.3 cm height, respectively. The distance between electrodes is 2.0 cm.

Figure 5. sEMG for Ag/AgCl membrane electrode with conductive gel.

Figure 6. sEMG for electrode C with conductive gel.

Figure 2. sEMG Electrodes C (left) and D (right), based on yarns FA (left) and FB (right).

RESULTS AND DISCUSSION As mentioned before, the main objective of this work was the comparison of textile based electrodes with Figure 7. sEMG for electrode D with conductive gel. conventional electrodes, made with Ag/AgCl. Two kinds were tested: one with a spoon shape and diameter 1.0 cm CONCLUSIONS and flexible disposable electrodes in a with 2.6x2.0 cm. This work presented textile based electrodes for use on To determine the skin-electrode interface impedance, the sEMG. The fabrication process allows embedding the electrodes were submitted to signals from 5 to 600 Hz, electrodes in the fabric, placed in any location, and a which accommodate the frequencies of interest for EMG. customized shape. The experiments made showed that the Figure 3 shows the behavior of textile electrode type B, electrode’s structure has influence in the signal quality. which was found to be very similar to the conventional Comparing to conventional electrodes, it was observed electrodes tested. The remaining electrodes showed signals with similar results. The advantage of more similar results. comfort to the user, since there is no need for adhesive, makes them a valid alternative that needs to be further explored.

REFERENCES [1] Silva, M., Catarino, A., Carvalho, H., Rocha, A., Monteiro, J., Montagna, G.,” Study of vital sign monitoring with textile sensor in swimming pool environment”. Proceedings of the IECON 2009, The 35th Annual Conference of The IEEE Industrial Electronics Society, 2009. [2] Silva, M., Catarino, A., Carvalho, H., Rocha, A., Monteiro, J., Montagna, G, “Textile sensors for ECG and respiratory frequency on swimsuits”, Proceedings of the Conference on Intelligent Textiles and Mass Customisation, 2009. [3] P. J. Xu, H. Zhang, X. M. Tao, "Textile-structured electrodes for electrocardiogram", Textile Progress, vol 40:4, 183-213, Figure 3. Skin-electrode impedance for electrode B. 2008. [4] M. Catrysse, R. Puers, C. Hertleer, L. Van Langenhove, H. Figures 4 to 7 present the resulting waveforms for van Egmond, D. Matthys. "Towards the integration of textile conventional and textile based electrodes. All electrodes sensors in a wireless monitoring suit", Sensors and Actuators, were used in pairs, together with a reference electrode, Vol 114, 302–311, 2004. placed in the byceps. As it can be seen, the signals show a [5] T. Linz, L. Gourmelon, G. Langereis, "Contactless EMG sensors embroidered onto textile", 4TH INTERNATIONAL similar shape, signal to noise ratio and RMS signals with WORKSHOP ON WEARABLE AND IMPLANTABLE BODY a signal correlation above 95%. It is very clear the SENSOR NETWORKS, IFMBE Proceedings, Vol 13, 29-34, difference between rest and contracting the muscle. 2007. [6] Rattfalt, M. Lind'en, P. Hult, L. Berglin, P. Ask, "Electrical characteristics of conductive yarns and textile electrodes for medical applications", Med Bio Eng Comput, Vol 45, 1251– 1257, 2007 [7] L. Rattfalt, M. Chedid, P. Hult, M. Lind'en, P. Ask, "Electrical Properties of Textile Electrodes", Proceedings of the Figure 4. sEMG for Ag/AgCl spoon-shape electrode with 29th Annual International Conference of the IEEE EMBS, 5735- conductive gel. 5738, 2007.

Physical Properties of PLGA Nanofiber Yarn with Potential Application Surgical Suture

Fatemeh Haghighat, Seyed Abdolkarim Hosseini Ravandi Department of Textile Engineering, Isfahan University of Technology, 84156, Isfahan, Iran [email protected]

STATEMENT OF PURPOSE Instrumentations: Two differently charged nozzles setup Electrospinning is a technique that can produce was applied to produce Poly(lactide-co-glycolide) nanofibers from many types of polymers using a strong (PLGA) nanofiber yarn [5]. In order to improvement of electric field. In particular, electrospinning process as physical properties of yarn, Post-treatment including heat method that can produce limited output can be appropriate setting was done on yarn. Tensile test of suture was for biomedical instruments such as surgical sutures for evaluated in two modes: knotted (with surgeon's knot) and certain applications. unknotted using the ear method [6]. Tensile test was In this research, several physical properties in associated carried out by zwick machine. Gauge length and cross with suture was investigated for Poly(lactide-co- head speed were 25mm and 25mm/min respectively. glycolide) (PLGA) nanofiber yarn electrospun using two In elastic recovery test, Moving grip moved away from differently charged nozzles. These characteristics consist constant grip with speed 1mm/min until caused 2% of tensile properties, elastic recovery and capillarity of extension in the yarn. Then movement direction of grip nanofiber yarn. was reversed until stress was zero in the yarn. For capillarity measurements, A liquid was used consist INTRODUCTION of single-distillation water with 0.2% non-ionic detergent Among biomaterials employ as implants in human body, and 0.5% acid red AV dye for observing the height of the surgical sutures found the largest groups of materials. liquid rise. With development of the synthetic absorbable polymers, these materials were used for sutures [1]. Among all RESULTS AND DISCUSSION asorbable biomaterials, copolymers and terpolymers of L- Tensile properties: Figure 1 demonstrates strength - lactide, glycolide and ɛ-caprolactone appear to be the extension curves for two modes of setted yarn (knotted most attractive in biocompatible applications [2]. and unknotted). Vibration curve of knotted yarn (figure Nanofibers are biocompatible and biodegradable and are 1b) is representative of knot slippage along the tension in used for the replacement of structurally or physiologically initial stages of the test. deficient tissues and organs in humans [3]. Therefore nanofiber yarn can be used for surgical suture as a material that is implanted in human body. The strength property is the most frequently reported physical characteristics of suture materials. There must be a proper match between the suture strength and the tissue strength [4]. Suture strength includes knotted and unknotted (straight pull) tensile strengths. Viscoelasticity is a property shared by all polymeric materials, including all natural and synthetic sutures. Remaining strain of suture as a result of creep may alleviate the approximation of wound edges and consequently the wound is not healing. Therefore elastic recovery test can be representative viscoelasticty of suture. As capillarity is related to the ability to transport bacteria, it also needs to be measured. No capillarity is desired in any case of suture application due to the spread of microorganisms with the body fluid in between the fibers in multifilament sutures.

APPROACH Materials: Poly(glycolide-co-lactide) (PLGA10:90) random copolymer was obtained from purac and Figure 1. Strength - extension curves for two modes of 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) from Merck yarn (a) unknotted and (b) knotted was used as the solvent of PLGA. Optimal concentration was found 4.5 wt%. Specific stress was decreased slightly in knotted yarn in comparison to straight. Stress distribution is a factor affecting the yarn strength. Knot appearance caused stress low. However setted yarn was appeared higher capillarity. concentration and therefore was reduced strength of yarn. Liquid transfer rate into yarn is influenced by yarn structure. Distribution of fibers into the yarn structure Elastic recovery: After removal of the applied force, the determines size and continuity of the capillary. nanofibers deformation may be divided up into an elastic part, which of setted yarn is located in more regular arrangement is recovered when the stress is removed, and a plastic or rather than raw yarn led to increase of capillary continuity permanent part. Quantitatively, it is convenient to use the and consequently higher capillarity. following definition: CONCLUSION elastic extension Over the years, new sutures are being developed, to better elastic recovery(%)  ×100 (1) respond to particular surgical needs. In this study, total extension physical properties of PLGA nanofiber yarn were Test results for samples before and after setting process investigated. Results showed appearance of knot was consist of elastic recovery and other parameters was reduced strength of suture. summarized in Table I. In regard to suture more elastic recovery is favorable.

Table I. Results of elastic recovery test Result showed elastic recovery of PLGA nanofiber yarn Before After after setting process was improved. parameters Capillarity is an unfavorable phenomenon in suture. setting setting Capillary rise of nanofiber yarn before and after setting Remaining extension (%) 67.9 41.4 was very low. Setting process slightly increased Elastic recovery (%) 32.1 58.6 capillarity because of nanofibers was aligned along the Elastic work (Nmm) 0.006 0.037 yarn axis and continuity of capillary was increased.

Plastic work (Nmm) 0.029 0.051 REFERENCES total work (Nmm) 0.035 0.088 [1] Pillai, C.K.S., and Sharma, C.P., “Review Paper: Absorbable Polymeric Surgical Sutures: Chemistry, According to the table elastic recovery of yarn after Production, Properties, Biodegradability, and setting process was improved. In 2% extension elastic Performance,” Journal of biomaterials applications, Vol. recovery is about 58% that increased 82% rather than 25, No. 4, pp. 291-366, 2010. before setting process. T-test showed that this difference [2] Channuan, W., Siripitayananon, J., Molloy, R., statistically was significant. and Mitchell, G.R., “Defining the physical structure and properties in novel monofilaments with potential for use Yarn capillarity: capillarity is one of the most important as absorbable surgical sutures based on a lactide physical characteristics associated with sutures. Inter-fiber containing block terpolymer,” Polymer, Vol. 49, No. 20, space in fibrous materials is in the form of capillaries that pp. 4433-4445, 2008. can be occupied by liquid. Therefore, in this stage, [3] Venugopal, J., and Ramakrishna, S., capillary rise of nanofiber yarn was investigated before “Applications of polymer nanofibers in biomedicine and and after setting process. Figure 2 demonstrates change of biotechnology,” Applied biochemistry and biotechnology, liquid traveling height as the function of time that Vol. 125, No. 3, pp. 147-157, 2005. obtained from analyzing the captured images during [4] Patel, K.A., and Thomas, W.E.G., “Sutures, liquid rising into the yarn. The capillary rise slow down as ligatures and staples,” Surgery (Oxford), Vol. 26, No. 2, the time passes and becomes constant (equilibrium pp. 48-53, 2008. height) over a period of time. [5] Dabirian, F., and Hosseini, S.A., “Novel Method for Nanofibre Yarn Production Using Two Differently Charged Nozzles,” FIBRES & TEXTILES in Eastern Europe, Vol. 17, No. 3, pp. 45-47, 2009. [6] Ben Abdessalem, S., Debbabi, F., Jedda, H., Elmarzougui, S., and Mokhtar, S., “Tensile and Knot Performance of Polyester Braided Sutures,” Textile Research Journal, Vol. 79, No. 3, pp. 247-252, 2009.

Figure 2. Change of capillary height with passing time before and after setting process

According to curve, capillary rise of yarn before and after setting is about 1.2 and 2.5 mm that both values are very Biodegradable Polymer Nanocomposites Using Polyvinyl Alcohol and Nanomaterials

K. Qiu and A. N. Netravali Department of Fiber Science & Apparel Design, Cornell University, Ithaca, NY 14853-4401 [email protected]; [email protected]

STATEMENT OF PURPOSE APPROACH Several biodegradable polymer nanocomposites were BC cellulose was cultured using Acetobacter fabricated using crosslinked and noncrosslinked xylinum, ATCC 23769 in soy flour extract (SFE) polyvinyl alcohol (PVA) and different nanomaterials containing culture medium at 30oC incubator for (Bacterial cellulose (BC), micro (nano) fibrillated 10 days [5-7]. MFC and HNTs were cellulose (MFC) and halloysite nanotube (HNTs)). individualized by several separation techniques. The goal of this research was to develop environment- Biodegradable polymer nanocomposites were friendly polymer nanocomposite with excellent tensile, fabricated using PVA resin and above mentioned thermal and water-resistant properties and controllable nanomaterals. Different crosslinking methods biodegradability, and deeply understand their relating were also applied to the nanocomposites to further mechanisms and corresponding applications. improve their properties. All the specimens were characterized for their chemical structure, as well INTRODUCTION as elemental composition, crystalline, thermal, PVA is a widely used thermoplastic and biocompatible tensile, water-absorbent, soluble properties and polymer. However, unlike most petroleum based biodegradability. polymers, it is one of the rare polymers with a carbon- carbon single bond backbone that is fully RESULTS AND DISCUSSION biodegradable in the presence of suitably acclimated FIGURE 1 shows SEM images of freeze dried BC microorganisms [1-4]. BC nanofibers produced by and freeze dried BC-PVA nanocomposite. In Acetobacter xylinum, are fully biodegradable and have FIGURE 1 (a), the BC network and porous same chemical structure as the plant-based cellulose. structure can be observed clearly at the surface of However, BC fibers display many unique the membrane. FIGURE 1 (b) shows the structure characteristics including high purity, high degree of of BC-PVA nanocomposite. PVA penetrated into polymerization, high crystallinity, high tensile strength, the BC network structure and filled in most of high modulus and strong biological adaptability [5-7]. pores of BC which were filled when the MFC can be obtained by mechanical treatment of pulp composite was hot pressed [1]. cellulose fibers to small diameter fibrils through refining and high-pressure homogenization processes (a) (b) [2]. The MFC has high aspect ratio and high tensile properties as a result of high orientation and crystallinity. Their modulus is estimated at 140 GPa and tensile strength between 2 and 6 GPa [2]. HNT based on aluminosilicate clay nanosheets that are naturally rolled to form hollow tubular structures are FIGURE 1. SEM images of freeze dried BC (a) and freeze mined from natural deposits [3]. Unlike other dried BC-PVA nanocomposite (b) nanostructured clays that must be exfoliated, HNTs naturally occur as cylinders with average diameters Table І lists the tensile properties (Young’s typically smaller than 100 nm and lengths ranging modulus, tensile strength and tensile strain) of from 500 nm to over 1.2 µm [3]. HNTs have been PVA, MFC-PVA nanocomposites as well as their used in many application fields [3]. corresponding glyoxal crosslinked specimens. The results indicate that MFC can reinforce PVA with Several biobased and biodegradable polymer excellent Young’s modulus and tensile strength. nanocomposites have been fabricated and In addition, the crosslinked nancomposites can characterized in this research [1-7]. Their mechanical, have even higher tensile properties [2]. thermal, physical properties have been enhanced while at the same time the water resistance and biodegradability have been controllably improved. TABLE І. Tensile properties of PVA, BC-PVA nanocomposites and CONCLUSIONS their corresponding crosslinked specimens The present study has shown that the fabrication Specimens Young’s Fracture Fracture and characterization of biodegradable PVA based modulus stress strain nanocomposites. Nanomaterials used in the (MPa) (MPa) (%) research including BC, MFC and HNTs. The PVA 248 34.1 331 nanocomposites have excellent thermal, (22.9)* (13.3) (15.4) mechanical and water-resistant properties as well Crosslinked PVA 666 47.7 184 as controllable biodegradability (Composting). (9.5) (7.5) (16.3) These properties can be further enhanced by MFC-PVA 1033 53.2 25.2 crosslinking. These biodegradable polymer (10 wt% MFC) (7.2) (5.6) (23.7) nanocomposites have the potential to replace Crosslinked 1404 53.7 29.6 traditional non-biodegradable plastic materials in MFC-PVA (9.4) (7.1) (16.8) many applications, including racket frame, ski (10 wt% MFC) pole, circuit board, automobile inside etc. *: Values in the parentheses are % coefficient of variation values.

ACKNOWLEDGMENT Figure 2 shows typical TGA thermograms obtained This work was partly supported by the National for the PVA, HNT-PVA nanocomposite and their Textile Center (NTC) and the Wallace Foundation. corresponding malonic acid crosslinked specimens [3]. Authors would like to thank Prof.s D. Luo, A. These TGA curves confirm that the HNT-PVA Baeumner and J. Rose of Cornell University. nanocomposite has better thermal stability than that of

PVA. This is because HNTs have better thermal REFERENCES stability than PVA. After crosslinking, the thermal [1] Qiu, K., Netravali, A. N., “Bacterial cellulose- stability for both PVA and HNT-PVA improved based membrane-like biodegradable composites more. using cross-linked and noncross-linked polyvinyl alcohol,” Journal of Materials Science, 47(16), 2012, 6066-6075. [2] Qiu, K., Netravali, A. N., “Fabrication and characterization of biodegradable composites (b) (d) based on microfibrillated cellulose and polyvinyl (a) (c) alcohol,” Composite Science and Technology, 72(13), 2012, 1588-1594. [3] Qiu, K., Netravali, A. N., “Halloysite nanotubes reinforced biodegradable nanocomposites using noncrosslinked and malonic acid crosslinked polyvinyl alcohol,” FIGURE 2. TGA of PVA (a), HNT-PVA nanocomposite (b), Polymer Composites, 2012, Submitted. crosslinked PVA (c) and crosslinked HNT-PVA nanocomposite (d) [4] Qiu, K., Netravali, A. N., “A composting

Figure 3 shows typical SEM photomicrographs study of membrane-like polyvinyl alcohol based showing the surface characteristics of PVA specimens resins and nanocomposites,” Polymer as a function of composting time. With the time Degradation and Stability, 2012, Submitted. increasing, fungal hyphae and deeper cracks spread [5] Qiu, K., Netravali, A. N., “‘Green’ composites everywhere on the surface of PVA specimen that based on bacterial cellulose produced using novel resulted in specimens breaking down into many small low cost carbon source and soy protein resin,” In: pieces after 120 days of composting. Also, Recent Advances in Adhesion Science & crystallinity, crosslinking and addition of fillers could Technology: Mittal Festschrift, Brill, 2012, help to control the degradation rate. Accepted. [6] Hong, F., Qiu, K., “An alternative carbon source from konjac powder for enhancing a b c production of bacterial cellulose in static cultures by a model strain Acetobacter aceti subsp. xylinus ATCC 23770,” Carbohydrate Polymers, 72(3), 2008, 545-549. Figure 3 SEM photomicrographs showing the surface characteristics [7] Netravali A. N., Qiu, K., “Bacterial cellulose of PVA specimens (a:0 day; b: 90 days; c; 120 days of composting) based ‘green’ composites,” US Patent Publication Number: US 2012/0129228 A1, 2012. Real-Time Control for Electrospun Nanofiber: Experimental Investigation of Electrospinning Physics

Yunshen Cai, Thierry Desire, Michael Gevelber Boston University Department of Mechanical Engineering [email protected]

RESEARCH OBJECTIVES AND ISSUES angle. For further research, we are still developing the We seek to develop real-time control for the experimental capability of the system: electrospinning (ES) process that achieves desired fiber 1) In order to understand the influence of RH on the ES diameter and rejects disturbances that change fiber diameter, process, plastic walls are developed to enclose the system. such as relative humidity (RH). To do this, it is important to Several RH control strategies were developed to adjust RH determine which process parameter measurements can be level in the enclosed system. correlated to fiber diameters. It is also important to 2) In order to view the forming of deposition area, the 3rd understand process dynamics and figure out the relation camera is applied to view the shape of the lower B/W between inputs and outputs. In addition, we also seek to region. Then there are a total of three cameras to view the find the operating regime (OR) (selection of flow rate, whole process and measure process parameters. applied voltage and other conditions to result fiber diameter), which maximizes production rate and achieve EXPERIMENTAL CAPABILITY DEVELOPMENT desired fiber diameters. 1. Approaches to adjust RH From previous experiments of aqueous solutions [1], it is In the RH control system, three approaches are developed found that RH plays a significant role in changing fiber to control RH in the enclosed system. diameter and measured current. One way RH affects ES a) Dry nitrogen flow (earlier experiment approach) process is that lower evaporation rates result in longer Infusing dry nitrogen into enclosed system can decrease solidification times. On the other hand, current measured in RH level. RH could stay at any level lower than ambient the fiber decreases while RH increases. We are RH for a long time by controlling flow rate. However, the investigating how RH influences the current. dry nitrogen flow might take charges out from the system. In addition, the observation of bending angle and Hence, we seek to find other strategies to adjust RH. deposition area suggest that bending/whipping (B/W) b) Infusing water vapor region stops expanding. We are investigating driven factors Infusing water vapor into enclosed system can increase RH of the expansion and the roles of evaporation rate, electrical level. RH could stay at any level above ambient RH for a force and surface tension play in B/W region. long time. However, the heated water vapor could increase the temperature in the system. SYSTEM OVERVIEW c) Salt bath Some saturated salt solutions could make ambient RH stay at a specific value. Magnesium chloride and magnesium nitrate hexahydrate saturated solutions are used in experiments, which can make ambient RH steady around 32% and 55%. However, the time constant of salt bath is long, around 1 hour. 2. Evaporation rates of non-aqueous solutions We seek to extend our experiments to non-aqueous solutions. Hence, in order to change the evaporation rate, different evaporation rate solvents, such as ethanol, 2-butanol and methanol are selected to make non-aqueous solutions. However, those solvents not only have different evaporation rate, but also have some other characteristics may influence the ES process, such as conductivity, viscosity and surface tension. 3. Imaging the bending/whipping zone Many articles (i.e. ‘Bending instability in electrospinning Fig. 1 Scheme of real-time ES measurement system of nanofibers’; A. L. Yarin; D. H. Reneker) regard B/W region as a cone. However, if it is true, according to the In order to understand process dynamics and the relation measured bending angle, the calculated deposition area between inputs and outputs in the system, a computer and a should be larger. It suggests that the shape of higher B/W DAQ card are applied to control all inputs, such as flow region is a cone, but the shape of lower B/W region is a rate and high voltage, and record all process parameters at cylinder (Fig. 2a). To prove this, we installed another the same time, i.e. relative humidity, current and bending camera (3rd camera, EOS camera) to view the shape of lower B/W region (Fig. 2b). The observed result suggests evaporation rate, which will determine the solidification that the B/W region stops expanding, which means that the time of jets. Evaporation rate will decrease 60% while RH deposition area is not linearly proportional to B/W angle. increases from 30% to 60%. However, the jet may stops Based on the data of 7% PEO/water (Mw 400,000), the stretching before it is solidified, because of viscoelastic of calculated shape of B/W region (Fig. 3) matches the model solutions. We are investigating the relation between we built (Fig. 2a). We are investigating the role of evaporation rate and stretch time. evaporation rate and force balance play in the B/W region. 2. Influence of RH on current Measured current in jet decreases with RH increasing [2]. The same trend was observed by using different approaches to adjust RH. There are four kinds of charge carriers in the ES system: ions in solutions, charged air, charged droplets and charged water vapor. We seek to understand how RH influences those carriers and transfer of charges. 3. Influence of RH on non-aqueous solutions For non-aqueous solutions, RH has little influence on evaporation rate of it. We are also interested in the influence of RH on non-aqueous solutions.

OPERATION REGION FOR NONAQUEOUS SOLUTIONS Fig. 2a The scheme of B/W region. The B/W region stops extending in the air at some point.

Fig. 4 The operating regime of non-aqueous solutions.

Fig. 2b The shape of lower bending region. The lower B/W A map of operating regime is useful to maximize the region is a cylinder. production rate and achieve the desired fiber diameter. 8% PVP/ethanol (Mw 1,300,000) and PVP/methanol solutions are used as an example in experiment. We have determined the upper and lower boundary of the OR (Fig. 4). We are investigating to map the distribution of fiber diameters to the OR of PVP non-aqueous solutions.

ACKNOWLEDGMENT We appreciate the funding support from the NSF (CMMI 0826106) and Army (W911QY-11-1-0014), and the contributions of David Ouk and Vicki Liu.

REFERENCES [1] X. Yan, M. Gevelber, “Investigation of Electrospun Fiber Diameter Distribution and Process Dynamics,” Fig. 3 The outline of 7%PEO/water experiment. L is the published in the Journal of Electrostatics, 68 (October calculated height that jet stops expanding. a) Blue line is 2010), pp. 458-264. the data of RH 36%; b) Red line is the data of RH 48%. [2] X. Yan, “Electrospinning of nanofibers: analysis of diameter distribution and process dynamics for control,” ROLE OF RELATIVE HUMIDITY IN ES PROCESS Thesis (Ph. D.)--Boston University, 2011. 1. Influence of RH on evaporation rate For aqueous solutions, RH is a critical factor for the Environmental Aging Study of AuTx® and Kevlar® Yarns and Fabrics

Judith B. Sennett U.S. Army Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts [email protected]

STATEMENT OF PURPOSE/OBJECTIVE AuTx® yarns and fabrics are composed of a copolymer which contains a para-aramid component and a benzimidazole functional group (monomer is diaminophenylbenzimidazole). These materials have Figure 2: PPTA come under recent scrutiny as potential candidates for the production of lighter weight, better-performing soft armor systems, mainly as alternatives to Kevlar® and other para-aramid based textiles. However, research and development of a new material will be at least partly based on knowledge of the material durability under a Figure 3: AuTx variety of environmental conditions. The purpose of this study is to investigate the retention of mechanical properties and ballistic performance of AuTx® yarns and fabrics after exposure to ultraviolet radiation and hygrothermal conditioning. Results will be compared to those obtained by analyzing properties of Kevlar® KM2 600 denier and Zylon® AS 1000 denier (poly p- Figure 4: PBO phenylene benzobisoxazole, PBO) materials after aging under identical conditions. For the ultraviolet radiation exposure study, yarn specimens were irradiated for two, four, six, and eight INTRODUCTION days. For hygrothermal conditioning, yarns were immersed in distilled water baths at elevated temperatures AuTx® yarns and fabrics are of Russian origin and were o initially based on a relatively simple homopolymer, SVM of 60, 80 and 100 C. Samples were removed for testing (translates as “super high modulus”), shown in Fig. 1. at seventeen and thirty-four days. Control yarns and This material was first produced in 1976 and was for conditioned yarns were evaluated using tensile testing to many years the main material used for flexible anti- determine retention of properties including tenacity, fragmentation and bullet proof vests and helmets for elongation to break, and elastic modulus. For the ballistic Russian military, government and private security and fragmentation studies, fabric panels measuring 38 cm organizations. In 1989 the next generation of Russian (15 in) square were cut from the roll materials of Kevlar aramid-copolymer fibers was created under the trade and AuTx, and arranged in layers of various name of Armos and put into large scale production for configurations. The AuTx fabric is a twill weave material composite applications. AuTx fibers appeared in 1997. (serge) that is available in basis weight of 110 or 120 g/m2. The Kevlar S706 fabric is a plain weave This fiber has very high strength (26-33 gf/den), high 2 modulus (100-140 GPa), and elongation at break from construction with a basis weight of 180 g/m . These textile packages (shoot packs) were conditioned in 2.6-3%. o o distilled water at 100 C and 80 C for 17 and 34 days. APPROACH The yarns used in this study were (1) Kevlar®, poly(p- RESULTS AND DISCUSSION phenylene teraphthalamide) (PPTA), (Fig.2); (2) AuTx, a After exposure periods were complete, yarn specimens copolymer of poly[5-amino-2-(p-aminophenyl) were evaluated to determine the degree of retained benzimidazole terephthalamide] (SVM) and PPTA (Fig. strength when compared to unexposed (control) materials. 3); and PBO, poly-p-phenylenebenzobisoxazole (Fig. 4). Ultraviolet radiation conditioning AuTx and PBO yarns displayed similar losses in tenacity after exposure to ultraviolet radiation, compared to either Kevlar 49 or to Kevlar KM2, which were more stable in this environment (Fig. 5). Figure 1: SVM

UV exposure study‐ AuTx , Kevlar & PBO Yarns 102.00 100.00 100.00 95.00 98.00 90.00 %

96.00 Control 85.00 V (exp)/ 17 days 80 C 80.00 50 94.00 Autx V50(con), 34 days 80 C Strength, 75.00 92.00

% Kevlar 49 70.00 17 days 100 C 90.00 65.00 Kevlar KM2 34 days 100 C

Retained 88.00 60.00 PBO 55.00 86.00 50.00 84.00 0 50 100 150 200 250 Condition Exposure to UV, time in hours Figure 7: AuTx V50 data Mil Std 662F 17 grain FSP Figure 5: UV exposure study 120 Hygrothermal conditioning For the yarns that were exposed to the most extreme 115 condition of 100 oC, there is a significant loss of tenacity for AuTx and PBO; much less so for KM2 (Fig. 6). For 110 Control o yarns conditioned at temperatures of 80 C or lower (AuTx V50 (exp)/ 17 days 80 C V50(con), 105 and KM2), there is only minimal loss of tenacity. % 34 days 80 C 17 days 100 C 100 34 days 100 C Hygrothermal study‐ 100oC 95 100.00 95.00 90 90.00 Condition %

R² = 1 85.00 80.00 Figure 8: Kevlar KM2 V50 data Mil Std 662F 17 grain

Strength, 75.00 Kevlar KM2 R² = 0.9988 FSP 70.00 AuTx 100C 65.00 PBO

Retained exposure period of eight days; in order of stability to UV 60.00 R² = 1 results were Kevlar 49 > Kevlar KM2 > AuTx ≈ PBO. 55.00 o 50.00 For the hygrothermal conditioning at 100 C for 34 days, 0 10203040 tensile strength retention was intermediate for AuTx Conditioned in H2O, time in days (75%) compared to Kevlar KM2 (88%) and PBO (56%). o o o For 80 C and and for 60 C hygrothermal conditioning, Figure 6: Hygrothermal exposure study at 100 C tensile strength retention was much higher for both KM2 AuTx. Kinetics analysis of the degradation of tensile Ballistic performance strength after hygrothermal conditioning displayed a Ballistic and fragmentation study of conditioned shoot second order mechanism with linear Arrhenius behavior packs were performed on hybrid AuTx and Kevlar KM2 and activation energies of 51.32kJ/mole (AuTx) and fabric shoot packages after exposure to elevated 40.29kJ/mole (KM2). Ballistic and fragmentation temperatures in distilled water. analysis of hygrothermally conditioned shoot packs of AuTx and Kevlar KM2 did not reveal correlated losses in For V50 fragmentation testing of AuTx (Fig.7), there is a strength when compared to tensile analysis of conditioned trend of lowered V50 results following prolonged yarns of these materials. The reason for the disparity exposures to elevated temperatures, however the greatest between yarn strength retention and ballistic performance reduction is only about 11%. V50 results from retention of the fabrics is unknown but may be related to fragmentation testing of conditioned shoot packs of the different chemical treatments and processing history Kevlar KM2 (Fig. 8) indicate that Kevlar fabric panels are of the two material forms. more stable after conditioning in elevated temperature liquid water than AuTx packages. REFERENCES 1. Kevlar KM2 Yarn and Fabric Strength Under Quasi- CONCLUSIONS Static Tension, Thomas J. Mulkern and Martin N. Environmental conditioning of the specimen yarns by Raftenberg, ARL-TR-2865, October 2002. exposure to ultraviolet radiation and to elevated 2. Knoff, W. F., Koralek, A. S., Eareckson, W. M., temperature liquid water was followed by mechanical “Prediction of Long Term Strength Retention of Kevlar testing of the conditioned yarns. All of the yarns Aramid Fibers in Aqueous Environments,” Annual exhibited sensitivity to ultraviolet radiation resulting in Meeting of the Marine Technology Society, September 7- significant drops in tensile strength during the maximum 9, 1994, Washington, D.C.

A Design Tool for Clothing Applications: Wind Resistant Fabric Layers

Phillip Gibson1, Jerry Bieszczad2, John Gagne2, David Fogg2 1U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, Massachusetts, USA 2Creare, Inc., Hanover, New Hampshire, USA [email protected]

INTRODUCTION APPROACH Windproof and wind resistant clothing layers are A protective clothing design tool under development by important in applications such as cold weather clothing Creare, Inc., for the U.S. military provides a physics- and military chemical and biological protective based computational framework for iterative modification ensembles. Completely windproof clothing provides and assessment of protective clothing systems [2]. protection from heat loss due to air penetration in cold Creare’s Individual Protection System Performance conditions, but can also become very uncomfortable when Model (IP SPM) is built on a foundation of advanced the wearer is working hard and generating a lot of heat computational fluid dynamic and experimental results, but and sweat. The same situation arises in protective the software itself is purposefully simplified to allow non- clothing – some ventilation through the fabric layers can expert users to modify clothing designs and assess the be very helpful in mitigating heat stress and extending consequences of various clothing aspects such as fit, wear time. Design tools that allow simultaneous closures, interfaces, material properties, layering, etc., assessment of factors such as wind penetration, heat upon comfort and protection. In this study we focus upon transfer, moisture transport, and permeation of toxic the use of the SPM tool to assess the relative importance substances can assist in developing new clothing systems of changing the air flow resistance of fabric layers upon that strike a good balance between protection and the calculated total heat transfer resistance of the clothing comfort. system.

We have shown previously that the wind resistance and RESULTS AND DISCUSSION aerosol filtration properties of clothing layers can be The Creare SPM can be configured to simulate a thermal controlled by the varying the deposition of electrospun manikin, which is an important tool in clothing comfort fiber membranes onto textile substrates [1] (Figure 1). research. Figure 2 shows baseline comparison results for 1010 the SPM thermal manikin calculated overall heat transfer coefficients as compared to some empirical correlations ) -1 obtained with humans [3] and thermal manikins [4], as 9 well as computational and analytical results from heated 10 cylinders [5]. 0.4 Heat Transfer Coefficent from Standing Human [3] 8 Thermal Manikin Correlation [4] 10 Correlation from Literature for Bare Cylinder in Cross-Flow [5] CFD Calculation for Bare Cylinder in Cross-Flow [5] Calculated from SPM Bare Manikin Model 0.3 Air Flow (m Flow Resistance Air

107 10-4 10-3 10-2 10-1 0.2 Electrospun Coating Level (kg/m2)

Fig. 1. Air Flow Resistance of Fabric Layer Modified by Electrospun Fiber Coating Level [1]. 0.1

Since nanofiber layers make it possible to control air flow / Watt) (m²-°C Resistance Thermal resistance over several orders of magnitude without 0 0 2 4 6 8 10 affecting other clothing properties, we are interested in the resulting consequences of using these materials in new Wind Speed (m/s) clothing designs. Electrospun elastomeric polyurethane Fig 2. Overall Heat Transfer Coefficent of SPM Thermal membranes are now used in commercial outerwear fabrics Manikin as a Function of Wind Speed. such as “NeoShell” by Polartec, Inc., and take advantage of this ability to “tune” air flow through the fabric without Figure 2 shows that the SPM results significantly significantly affecting other properties such as thermal underpredict the total heat transfer coefficients at low air insulation or water vapor diffusion (breathability). velocities, and are in better agreement above 5 m/s. Previous computational simulations examined the effect flow conditions for the less-permeable jacket). Suit C is of varying only the fabric air flow resistance (all other wind-resistant, and also has a much looser fit which traps properties kept constant) and calculated the overall heat more air under the clothing, resulting in increased thermal and mass transfer coefficient from fabric-covered insulation properties for that configuration. cylinders as an analog to the human body [5]. Wind Speed (meters/second)

1 0 15 30 40 Fabric Air Flow Resistance (R ) = 1x109 m-1 1.5 D Suit C (Jacket and Pants 8 with high air flow resistance, R = 1x10 9 -1 0.02 D 1x10 m , with looser fit) 7

R = 1x10 C / Watt) -°C / Watt) -°C D o - 2

1.0 Suit B (Jacket changed to 2 high air flow resistance, 1x109 m-1) 0.1 0.01 0.5

R = 1x106 Clo ) ( Insulation Thermal Suit A (Jacket and Pants with D Bare SPM low air flow resistance,

7 -1 (m Resistance Thermal Bare Cylinder (No Fabric Layer) Thermal Manikin 1x10 m ) Thermal Resistance (m Resistance Thermal 0 0 0.01 0 5 10 15 20 1 2 5 10 Wind Speed (miles/hour) Wind Speed (m/s) Fig. 5. Use of SPM for Simple Design Study.

Fig 3. Overall Heat Transfer Resistance of Fabric-Covered Cylinders in Cross-Flow Conditions at Various Wind Speeds CONCLUSIONS [2]. Simplified clothing design tools would greatly enhance our ability to iteratively vary clothing design features and The SPM allows a very similar computation to be carried examine the consequences for comfort and protection. for a more realistic clothing and body geometry. A Further verification and validation with experimental similar relationship of air flow with clothing is shown in thermal manikin measurements will be required for a Figure 4; air flow resistance is more important at high variety of clothing ensembles, so that results predicted wind speeds, and once the fabric becomes “wind-proof,” with the model can be used as a reliable design tool in the any further increase in air flow resistance does not future. significantly affect heat transfer. ACKNOWLEDGMENT Funding for this work was provided by the United States 0.20 Defense Threat Reduction Agency. Fabric Air Flow Resistance (R ) = 1x109 m-1 D R = 1x108 D REFERENCES 0.15 R = 1x107 1. Gibson, P., Schreuder-Gibson, H., Rivin, D., "Transport D -°C / Watt)

2 Properties of Porous Membranes Based on Electrospun R = 1x106 D Nanofibers,” Colloids and Surfaces A: Physicochemical and Engineering Aspects 187-188, pp. 469-481, 2001. 0.10 2. Bieszczad, J., “Physics-Based Modeling and Test Methods for Improving Aerosol Protection and Reducing Thermal Burden of IPE,” 2011 Chemical and Biological Defense 0.05 Science and Technology Conference, Las Vegas, NV, November 14-18, 2011. 3. Danielsson, U., “Windchill and the Risk of Tissue Thermal Resistance (m Bare SPM Manikin (No Fabric Layer) Freezing,” Journal of Applied Physiology 81 (6), pp. 2666- 0 0 2 4 6 8 10 2673, 1996. 4. Virgílio, A., Oliveira, M., Gaspar, A., Francisco, S., Wind Speed (m/s) Quintela, D., “Convective Heat Transfer from a Nude Body under Calm Conditions: Assessment of the Effects of Figure 4. System Performance Model (SPM) Predictions for Walking with a Thermal Manikin,” International Journal of Variable Air Flow Resistance of Fabric Layer. Biometeorology 56 (2), pp. 319-332, 2012. 5. Gibson, P., "Modeling Heat and Mass Transfer from Fabric- An example of the use of the SPM to examine some Covered Cylinders," Journal of Engineered Fibers and simple clothing design variations is shown in Figure 5. Fabrics 4 (1), pp. 1-8, 2009. Suit A and Suit B vary only in the air flow resistance of the jacket (causing slightly more heat loss at higher air Durable Superhydrophobic Fabrics Prepared by Surface Coating of Nanoparticle/Elastomeric Polymer Composite

Hua Zhou, Hongxia Wang, Haitao Niu, Adrian Gestos, Tong Lin Institute for Frontier Materials, Deakin University, Geelong, VIC 3217, Australia [email protected]

INTRODUCTION containing FAS to form a coating solution. This coating Superhydrophobic surfaces with a water contact angle solution was then directly applied onto the fabrics using (CA) greater than 150° and low contact angle hysteresis dip-coating method. After dip-coating, the fabrics were have attracted tremendous attention over the last decade left at room temperature to remove the solvent, followed in both academic and industrial areas [1-3]. by curing at 110° for 30 minutes. The major issue facing existing superhydrophobic A plain weave polyester fabric was mainly used as a fabrics is low washing and abrasion durability. The model substrate. After the coating treatment, the fabric conventional strategy to improving the durability typically showed a superhydrophobic surface. When water (10 µL) involves crosslinking the coating layer and/or establishing was placed on to the coated fabric, a nearly sphere-like covalent bonding between the coating and substrate [4]. water droplet was formed (Fig. 1c). The coated surface However, only limited success has been achieved in this had a water contact angle (CA) of 171° and sliding angle area so far. (SA) of 2º, indicating a very high superhydrophobicity. Recently, Wang et al [5] introduced a ‘bio-inspired’ When water was dropped on to the pristine fabric, the durable self-healing ability into the superhydrophobic water completely spread into the fabric as shown in Fig. coating, which represents an important development in 1b. A hierarchical surface roughness can be observed the area of superhydrophobic fabrics. from scanning electron microscopy (SEM) images as In our daily life, some polymeric materials have shown in Fig. 1e. shown excellent durability even if they have no self- healing function. Taking tires as an example, the basic ingredients of tires are and carbon black. However, the crosslinked rubber contains well-dispersed carbon black make tires very robust to withstand thousands of kilometers of running with tons of loading. Inspired by this classic nanocomposite, we have used polydimethylsiloxane (PDMS), silica nanoparticles and FIGURE 1 a) Procedure to prepare the coating solution and superhydrophobic fabrics; b) & c) The pictures of water drops (10 µL fluorinated alkyl silane (FAS) as materials to produce a each) on the b) untreated and c) treated polyester fabrics; d) & e) SEM superhydrophobic coating on fabrics. This simple and low images of d) pure polyester fabric and e) silica/PDMS/FAS treated cost coating showed remarkable durability against strong fabric (PDMS 1.0 wt%, FAS 2.5 wt%, and nanoparticle 1.5 wt%). acid, strong alkali, repeated machine washes, boiling in water and severe abrasion damages, whilst retained its Fig. 2a shows the change of CA and SA with laundry superhydrophobicity. cycles. With increasing laundry cycles, the CA slightly decreased, while the SA had a little increase. Both APPROACH changes in CA and SA were less than 5° after 500 Silica nanoparticles were first dispersed in washing cycles, indicating the excellent durability to polydimethylsiloxane (PDMS)/ tetrahydrofuran (THF) washing. The changes in CA and SA with abrasion cycles solution (Elastomer Base and Curing Agent mixture 10:1) are shown in Fig. 2b. The CA remained at 170° after the with the aid of ultrasonication to form homogeneously first 2,000 cycles under both pressure conditions. dispersed particulate solution prior to coating treatment. Although the CA reduced with further increasing the The as-prepared coating solutions were applied onto abrasion cycles, the coated polyester fabrics can withstand fabric substrates by dipping method. The coatings were at least 28,000 cycles of abrasion damages without losing then dried at room temperature for 30 minutes, and further their superhydrophobicity. cured at 110° for 30 minutes. a 180 40 b180 40 160 30 160 30 12 kPa )

RESULTS AND DISCUSSION ° ( 9 kPa 140 20 140 20 12 kPa CA (°)

The chemical structures and the procedure used to SA SA (°) CA (°) 9 kPa prepare the coating solution are presented in Fig. 1a. 120 10 120 10

Hydrophobic silica particles were prepared by co- 100 0 100 0 0 100 200 300 400 500 0 5 10 15 20 25 30 hydrolysis and co-condensation of tetraethylorthosilicate Laundry cycles (times) Abrasion kilo- cycles and FAS under an alkaline condition [6]. After purification, the FAS functionalized silica nanoparticles FIGURE 2. a) Water contact angle (CA, -□-) and sliding angle (SA, -●-) change with washing cycles; b) CA and SA as a function of abrasion were dispersed into a PDMS/THF solution also cycles under different loading pressures. Besides the excellent washing and abrasion durability, breathability of the fabric is poor. As shown in Fig. 5a, the coated fabric can also withstand boiling water without after the superhydrophobic treatment, the bending changing its superhydrophobicity. Fig. 3 shows the modulus increased just slightly in both the warp and weft change of water CA and SA with the boiling time. After 5 directions, indicating that the superhydrophobic coating hours of boiling in water, the coated fabric still had a doesn’t influence the natural handle property of fabric. superhydrophobic surface. Fig. 5b shows the air permeability of treated fabrics

180 40 before and after the superhydrophobic treatment. The air 3 2 160 30 permeability decreased only slightly from 17.9 cm /cm /s to 16.5 cm3/cm2/s after coating, suggesting that the coated 140 20 fabric still maintained good breathability. SA (°) CA (°) 10 120 10 ) 2 Warp 20 /s) 8 a 2 b 100 0 Weft 16 /cm

012345 3 Boiling Time (hour) 6 12

4 8 FIGURE 3. CA and SA change with the boiling time. 2 4

Permeability (cm Bending modulus (g/cm modulus Bending 0 0

Stain resistance of the coated fabric was evaluated by Untreated fabric Treated fabric Untreated fabric Treated fabric staining fabric with a natural cherry powder, a standard FIGURE 5. a) Bending modulus and b) air permeability of the polyester colorant required for stain resistant test by following the fabrics before and after Silica/PDMS/FAS coating treatment. standard procedure. After 24 hours of staining, the coated fabric was easily cleaned by rinsing with water (Fig. 4a), CONCLUSION further indicating the excellent stain resistance of the We have demonstrated that a crosslinked elastomeric coating. The excellent stain resistance of the coating here thin coating possessing a nanocomposite structure with a suggests that it could also be useful for fabrics in anti- rough and low free-energy surface can endow fabrics with fouling of organic contamination applications. a highly durable superhydrophobic surface. Such a We also found that the superhydrophobic coating was durable, robust, superhydrophobic coating may be useful very stable in strong acid and strong base. When the for developing self-cleaning protective textiles for various coated fabric was immersed in an acid H2SO4 (pH = 1) or functional applications. a base KOH solution (pH = 14) for 24 hours, the fabrics were then rinsed with water and dried in room KEYWORDS: Superhydrophobic, Durability, PDMS, temperature. As shown in Fig. 4b, after the strong acid or Nanocomposite, Fabric Coating strong alkali treatment, water on the fabric can still form round ball. The contact angle changed to 168.5±3.0º and ACKNOWLEDGMENT 168±4.0º after 24 hours of immersing in the H2SO4 and Funding support from Australia Research Council through the KOH (pH = 14) solutions, respectively. The a Discovery project and Deakin University through its superhydrophobic coating is therefore durable enough to Central Research Grant scheme is acknowledged. resist strong acid and alkali attacks. REFERENCES [1] A. Nakajima, A. Fujishima, K. Hashimoto, T. Watanabe, Advanced Materials 1999, 11, 1365. [2] M. Miwa, A. Nakajima, A. Fujishima, K. Hashimoto, T. Watanabe, Langmuir 2000, 16, 5754. [3] M. Ma, M. Gupta, Z. Li, L. Zhai, K. K. Gleason, R. E. Cohen, M. F. Rubner, G. C. Rutledge, Advanced Materials 2007, 19, 255. [4] Y. Zhao, Z. Xu, X. Wang, T. Lin, Langmuir 2012, 28, FIGURE 4. a) Photos of uncoated (top) and coated (bottom) fabrics after being soaked in staining solution, drying, and rinsing with water and 6328. then dry; b) Water droplets (10 µL each) on the treated fabric before and [5] H. Wang, Y. Xue, J. Ding, L. Feng, X. Wang, T. Lin, after immersing in strong acid or strong base solutions for 24 hours. Angewandte Chemie International Edition 2011, 50, 11433. Fabric bending modulus is an indication of the fabric [6] H. Wang, J. Fang, T. Cheng, J. Ding, L. Qu, L. Dai, X. handle property. The higher the bending modulus, the Wang, T. Lin, Chemical Communications 2008, 877. more rigid the fabric is, and the fabric is less comfortable to wear, particularly if the air permeability of

Electrospun Carbon Nanofiber Webs with Controlled Density of States for Sensor Applications

Xianwen Mao, Gregory C. Rutledge, and T. Alan Hatton Department of Chemical Engineering, Massachusetts Institute of Technology [email protected], [email protected]; [email protected]

INTRODUCTION RESULTS AND DISCUSSION In molecular and biomolecular electrochemistry, The scanning electron microscopy (SEM) images of the carbonaceous materials are of enormous interest, mainly due to electrospun CNF webs synthesized at different temperatures are their superior electrocatalytic activity for various chemical and shown in Figure 1. It can be seen that the porous CNF webs biological systems.[1] The control of heterogeneous electron consist of fibers with diameters around 250 nm with a slight transfer kinetics through judicious design and structural decrease at a higher carbonization temperature. In addition, the manipulation of advanced carbon materials is of importance in BET surface areas of CNF1000, CNF1100, and CNF1200 the fabrication of many electrochemical devices such as determined by nitrogen adsorption isotherm are 19.5, 27.8, and biological sensors.[1c, 2] Common strategies to accomplish this 58.8 m2/g, respectively, indicating that a higher synthesis control include modification of surface chemistry,[1c] variation temperature results in a more porous structure. of graphene orientation,[3] and manipulation of surface (a) (b) (c) roughness.[4] These strategies, however, offer little control over the density of electronic states (DOS) near the Fermi level, which plays a crucial role in the electrochemical activity of [1c, 5] electrode materials. Lack of direct control on the intrinsic 2 µm 2 µm 2 µm properties (i.e., DOS) of the electrodes results in an inability (1) Figure 1. Scanning electron microscopy (SEM) images of (a) CNF1000, to modulate kinetics for outer-sphere systems because their (b) CNF1100 and (c) CNF1200. kinetic behavior is only affected by the DOS of the electrode, and (2) to alter universally the kinetics for different types of Control of graphite concentration and density of electronic inner-sphere systems since one particular strategy usually can states for the electrospun carbon nanofiber webs is confirmed by only influence the kinetics of a specific inner-sphere system, not X-ray photoelectron spectroscopy (XPS) C 1s spectra, Raman all of them. Also the direct electron transfer (DET) with many spectroscopy, electron energy loss spectroscopy (EELS) and redox enzymes strongly depends on the DOS of the supporting ultraviolet photoelectron spectroscopy (UPS). These results are electrode.[6] Therefore development of an electrode with summarized in Figure 2. controlled DOS is necessary to modulate the DET efficiencies (a) (b) D with enzymes for many applications such as highly selective CNF1100 G CNF1200 [7] [8] [9] biosensors, bioelectronics, enzyme catalysts, and biofuel CNF1000 CNF1100 [10] cells. CNF1200 CNF1000 Electrospinning is a simple and versatile technique to 286 285 284 Intensity (a.u.) Intensity produce continuous nanofibers from various organic and (a.u.) Intensity inorganic materials.[11] Carbon nanofibers (CNFs) synthesized via electrospinning and subsequent carbonization have attracted 300 295 290 285 280 800 1200 1600 2000 Binding energy (eV) -1 considerable attention mainly because their structures and Wavenumber (cm )

[12] (c) (d) properties can be easily adjusted by processing conditions. π* σ* CNF1000 The electrochemical applications of electrospun CNFs are CNF1200 mostly related to the development of energy storage devices CNF1100 [13] [14] CNF1000 E including supercapacitors, lithium ion batteries, and fuel 311 eV F [15] CNF1100 cells. Only a few reports focus on sensor applications of the CNF1200 Intensity (a.u.) Intensity electrospun CNFs, the electroanalytical activities and 288 eV (a.u.) Intenstiy

biosensitivities of which are often adjusted through the use of an 280 290 300 310 320 330 3 2 1 0 -1 additional active component, such as loading and deposition of Energy loss (eV) Binding energy (eV) metal nanoparticles onto the fibers.[16] Figure 2. Evidence for control of graphite concentration and DOS for the In contrast, our work concentrates on manipulation of the CNF webs synthesized at different carbonization temperatures. (a) High- intrinsic electronic properties of the electrospun CNFs for resolution X-ray photoelectron spectroscopy (XPS) C 1s spectra (the electrochemical sensing applications. We present a simple and inset is an enlarged dotted rectangle). (b) Raman spectra showing the D and G bands. (c) Electron energy loss spectra (EELS) showing the π* highly effective strategy to adjust the electrochemical activities and σ* bands. (d) Ultraviolet photoelectron spectra (UPS) showing the of electrospun CNF webs via controlling their DOS by DOS near the Fermi energy. processing conditions. We found that the use of electrospun CNF webs with adjustable DOS can modulate electron transfer High resolution transmission electron microscopy (HR- kinetics and efficiencies for various chemical and biological TEM) and atomic force microscopy (AFM) were used to probe systems. This further suggests that our strategy to control the surface nanostructures of the carbonized fibers. The HR- electron transfer processes can apply to different types of redox TEM and AFM images of the CNF surfaces are shown in Figure species, which is highly challenging since their electron transfer 3. behaviors are usually affected by different factors.[1c]

(a) 3nm 3nm 3nm redox systems and adjustable DET efficiencies for Cyt c. HRP- modified CNF webs with a high DOS exhibited effectively the desired electrocatalytic response. Our findings indicate the utility of these materials in molecular and biomolecular electrochemistry, and enable novel applications for carbonized electrospun nanofiber webs in sensing and electrocatalysis. CNF1000 CNF1100 CNF1200 (b) 2.6 mV 2.6 mV 2.6 mV REFERENCES [1] a) J. M. Saveant, Chem Rev 2008, 108, 2111; b) J. M. Savéant, Elements of Molecular and Biomolecular Electrochemistry; Wiley: New York, 2006. c) R. L. McCreery, Chem Rev 2008, 108, 2646. 40 nm 40 nm CNF1000 CNF1100 CNF1200 40 nm [2] a) I. Dumitrescu, P. R. Unwin, J. V. Macpherson, Chem −2.6 mV −2.6 mV −2.6 mV Commun 2009, 6886; b) M. Pumera, Chem Soc Rev 2010, 39, 4146. Figure 3. CNF surface nanostructures. (a) High-resolution transmission electron microscopy (HR-TEM) images (the insets are Fourier [3] a) A. Ambrosi, T. Sasaki, M. Pumera, Chem-Asian J 2010, 5, transforms of the corresponding TEM micrographs). (b) Atomic force 266; b) E. C. Landis, K. L. Klein, A. Liao, E. Pop, D. K. Hensley, microscopy (AFM) amplitude images. A. V. Melechko, R. J. Hamers, Chem Mater 2010, 22, 2357. [4] A. Ueda, D. Kato, R. Kurita, T. Kamata, H. Inokuchi, S. Next we examine the electrochemical activity and Umemura, S. Hirono, O. Niwa, J Am Chem Soc 2011, 133, 4840. biosensitivity of the CNF webs with differing DOS. The [5] a) W. J. Royea, T. W. Hamann, B. S. Brunschwig, N. S. Lewis, J 0 Phys Chem B 2006, 110, 19433; b) R. Parsons, Surf Sci 1964, 2, obtained apparent electron transfer rate k app for an outer-sphere system and three different kinds of inner-sphere systems are 418. [6] C. Leger, P. Bertrand, Chem Rev 2008, 108, 2379. shown in Figure 4a and 4b, respectively. In addition, the direct [7] L. Stoica, R. Ludwig, D. Haltrich, L. Gorton, Anal Chem 2006, electron transfer efficiencies of the CNF webs with redox 78, 393. enzymes were studied. The DET-type electrocatalytic activity [8] M. Pita, E. Katz, J Am Chem Soc 2008, 130, 36. for cytochrome c is presented in Figure 4c. Furthermore, the [9] K. A. Vincent, X. Li, C. F. Blanford, N. A. Belsey, J. H. Weiner, horse radish peroxidase (HRP)-modified CNF web showed F. A. Armstrong, Nat Chem Biol 2007, 3, 760. bioelectrocatalytic activity towards reduction of hydrogen [10] a) J. A. Cracknell, K. A. Vincent, F. A. Armstrong, Chem Rev peroxide; the results are illustrated in Figure 4d. 2008, 108, 2439; b) S. C. Barton, J. Gallaway, P. Atanassov, Chem this work literature results (a)0 (b) 10 4 Rev 2004, 104, 4867; c) M. Hambourger, M. Gervaldo, D. Svedruzic, P. W. King, D. Gust, M. Ghirardi, A. L. Moore, T. A. 3 -1 Moore, J Am Chem Soc 2008, 130, 2015. 10 (cm/s) [11] a) D. Li, Y. N. Xia, Adv Mater 2004, 16, 1151; b) Y. Dzenis, -3 -3 2 (cm/s)

-2 *10 Science 2004, 304, 1917. 0 app

k 10 app 0 1

k [12] M. Inagaki, Y. Yang, F. Y. Kang, Adv Mater 2012, 24, 2547. [13] a) C. Kim, B. T. N. Ngoc, K. S. Yang, M. Kojima, Y. A. Kim, -3 10 0 Y. J. Kim, M. Endo, S. C. Yang, Adv Mater 2007, 19, 2341; b) Q. H. Guo, X. P. Zhou, X. Y. Li, S. L. Chen, A. Seema, A. Greiner, H. Q. Hou, Journal of Materials Chemistry 2009, 19, 2810; c) B. H. 3+/2+ Fe(CN) 3-/4- DA Fe 6 Kim, K. S. Yang, H. G. Woo, Electrochem Commun 2011, 13, 1042; d) H. T. Niu, J. Zhang, Z. L. Xie, X. G. Wang, T. Lin, Carbon (c) (d) 2011, 49, 2380; e) B. H. Kim, K. S. Yang, Y. A. Kim, Y. J. Kim, B. 8 0.5 CNF1200 0 An, K. Oshida, J Power Sources 2011, 196, 10496. 6 a )

2 CNF1100 4 -0.5 b [14] a) Y. Yu, L. Gu, C. L. Wang, A. Dhanabalan, P. A. van Aken, 0 -1 c J. Maier, Angew Chem Int Edit 2009, 48, 6485; b) C. Kim, K. S. A/cm 2 CNF1000 d  -1.5 -1 0 CNF Yang, M. Kojima, K. Yoshida, Y. J. Kim, Y. A. Kim, M. Endo, Adv e I (mA) -2 -2 HRP-CNF -2 (mA) Current Funct Mater 2006, 16, 2393; c) Y. Yu, L. Gu, C. B. Zhu, P. A. van -4 -2 0 Current ( -2.5 e 10 10 10 -4 [H O ] (g/L) Aken, J. Maier, J Am Chem Soc 2009, 131, 15984; d) L. W. Ji, K. H. -3 2 2 -6 -0.5 0 0.5 -0.8 -0.6 -0.4 -0.2 0 0.2 Jung, A. J. Medford, X. W. Zhang, Journal of Materials Chemistry Potential (V) Potential (V) 2009, 19, 4992; e) L. Zou, L. Gan, R. T. Lv, M. X. Wang, Z. H. Figure 4. The adjustable electrochemical activity and biosensitivity of Huang, F. Y. Kang, W. C. Shen, Carbon 2011, 49, 89. 0 the electrospun CNF webs. (a) Comparison of k app with literature [1c] 3+/2+ 0 [15] M. Y. Li, G. Y. Han, B. S. Yang, Electrochem Commun 2008, results for an outer-sphere system, Ru(NH3)6 . (b) k app for three 10, 880. different types of inner-sphere systems (Fe3+/2+, DA, and 3−/4− [16] a) J. S. Huang, D. W. Wang, H. Q. Hou, T. Y. You, Adv Funct Fe(CN)6 ).(c) Background-subtracted cyclic voltammograms of 100 Mater 2008, 18, 441; b) G. Z. Hu, Z. P. Zhou, Y. Guo, H. Q. Hou, µM Cyt c on the CNF webs. (d) Cyclic voltammograms corresponding S. J. Shao, Electrochem Commun 2010, 12, 422; c) Y. Liu, D. W. to the electrocatalytic reduction of H O by a horse radish peroxidase 2 2 Wang, L. Xu, H. Q. Hou, T. Y. You, Biosens Bioelectron 2011, 26, (HRP)-modified CNF1200 web; concentration of H2O2 in g/L: a) 0.001, b) 0.005, c) 0.025, d) 0.05, e) 0.250, f) 0.5. The inset shows the 4585; d) Y. Liu, H. Q. Hou, T. Y. You, Electroanal 2008, 20, 1708; amperometric response at the potential of −0.60 V of a HRP-modified e) Y. Liu, J. S. Huang, H. Q. Hou, T. Y. You, Electrochem Commun CNF web, and of an unmodified CNF web. 2008, 10, 1431.

CONCLUSIONS KEYWORDS We have demonstrated a new strategy to develop a sensing Molecular electrochemistry, biosensor, electrospinning, carbon platform with exceptional electrochemical activity and nanofiber, electron transfer. biosensitivity. The DOS of the CNF webs can be easily varied by controlling their nanosized graphite concentration through ACKNOWLEDGMENT manipulation of carbonization conditions. The CNF webs This work was supported by U.S. Department of Energy. showed controlled kinetic behavior for four different types of

Flexible and Transparent Fiber-Based Ionic Diode Fabricated from Oppositely Charged Microfibrillated Cellulose

Xiaodan Zhang1, Wei Zhang2, Youjiang Wang1, Yulin Deng2 1School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30313, USA 2School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA [email protected]

INTRODUCTION APPROACH The unidirectional current behavior can be MFC was prepared from bleached draft soft wood traditionally found in semiconductor diodes by pulp by mechanically force. The p-type(anionic) scattering electrons and holes to form a depleted MFC was prepared by an oxidation and sulfonation region, which is called p-n junction. Recently, method: organic diodes have attracted great research interest because of their unique applications in flexible electronics. Although some researches employ “paper-like” plastic polymers to fabricate p-n junctions, none of them have used real cellulose- based paper. Hereby, we report a transparent, The n-type(cationic) MFC was prepared by a flexible, green fiber-based ionic diode(FID) made of chemical reaction between MFC and 2,3- two oppositely charged microfibrillated epoxypropyltrimethylammonim chloride. cellulose(MFC) sublayers. The current rectification ratio is around 15 at ±5 V and exhibits good repeatability at room temperature. Unlike the conventional p-n junctions using electrons and holes as charge carriers, the FID relies on transportation of The thus made p-type MFC was poured in a dish to ions to conduct current. The asymmetric charge half-dry and then n-type MFC was carefully poured distribution between the two sublayers will help on the top to form bi-layer FID. selectively transport cations and anions under positive and negative bias, to allow an electric current RESULTS AND DISCUSSION to pass in only one direction. It was found that the moisture content, thickness of paper, scanning frequency will influence the performances of the diode paper. The diode made of microfibrillated cellulose(MFC) has outstanding optical, mechanical, biological advantages which especially can be envisioned to be applied in biomedical and environmental-friendly electronic areas.

STATEMENT OF OBJECTIVE 1) Chemically modify MFC with positive and negative charge; 2) Characterize the morphology of p-, n-type MFC; 3) Fabricate ionic paper diode with oppositely charged MFC. 4) Test the I-V curve of FID; 5) Identify the important factors which will influence the performance of MFC-based diode. 6) Figure 1. SEM images of : a) anionic (p-type) MFC Study the mechanism of MFC-based diode. (scale bar: 300nm); b) cationic (n-type) MFC (scale bar: 200 nm); c) transparency of a 60 μm thickness FID; d) Flexibility of FID.

Figure 2. a) Current as a function of applied bias for FID; b) current as a function of applied bias for the p- type and n-type MFC paper.

The diameters of p-, n- type MFC are in nano-scale as shown in Figure 1a, b. The thus made FID is quite Figure 4. a) Rectifying behavior of the MFC diode transparent and flexible as indicated in Figure 1c, d. under AC signal frequency of 10 mHz. The effects of The I-V curve of only p-type or n-type MFC appears different factors that influence the current-voltage to be symmetric about original point(Figurre 2b). But behaviors are shown in: b) moisture content, c) MFC if the p-n FID is tested, FID appears to have a paper thickness and d) voltage scanning frequency. rectification effect of 15 at ±5V. The mechanism for FID is illustrated in Figure 3. The positive and negative charged MFC sublayers can selectively CONCLUSIONS transport these ions under different bias, leading to Transparent, flexible and green FID was successfully current flow in only one direction. made by combining p-type and n-type MFC sublayers together to allow current flow in only one direction. The FID has a rectification effect of 15 at ±5V. The I-V behavior of FID can be influenced by moisture content, thickness and frequency. FID was promising to be used in biomedical areas.

KEYWORDS Microfibrillated Cellulose; Nanofibrils; Ionic diode; Transparent; Electronic paper

ACKNOWLEDGMENT Thanks go to Institute of Paper Science and Technology at Georgia Tech for supporting this research through a scholarship awarded to X. Zhang.

REFERENCES 1. H. Reiss, Journal of Chemical Physics, 21 (1953) 1209-1217. 2. B. Lovrecek, A. Despic, J.O.M. Bockris, Journal of Physical Chemistry, 63 (1959) 750-751. 3. J. Zhang, N. Jiang, Z. Dang, T.J. Elder, A.J. Figure 3. a) Schematic illustration of the fabrication Ragauskas, Cellulose, 15 (2008) 489-496. of FID. b) demonstration of ionic current rectification 4. L. Yan, H. Tao, P.R. Bangal, Clean-Soil Air mechanism for the diode MFC paper under forward Water, 37 (2009) 39-44. or c) backward bias. 6. O.J. Cayre, S.T. Chang, O.D. Velev, Journal of the American Chemical Society, 129 (2007) 10801- 10806.

Polyacrylonitrile-Metal Organic Framework (MOF) Composite Electrospun Nanofibers Designed to Remove Chemical Warfare Agent Simulants from a Solution

Laura E. Lange, Fredrick O. Ochanda, S. Kay Obendorf, Juan P. Hinestroza Cornell University [email protected]; [email protected]; [email protected]

STATEMENT OF PURPOSE MOFs are of interest is due to their large surface The goal of this research was to create a area compared to their weight and their lightweight nonwoven composite material with controllable pore size leading to an increased the ability to adsorb and degrade potential for selectively adsorbing chemicals and organophosphates. gases6, 7, 8, which could include chemical warfare agents and pesticides. INTRODUCTION Organophosphates (OPs) are a group of organic APPROACH phosphorous compounds that are of wide interest Using electrospinning, a fiber mat with MOF- due to their use as neurotoxic 199 enmeshed in polyacrylonitrile (PAN) pesticides/insecticides. These compounds pose a nanofibers was developed (Figure 1). MOF-199 threat to humans through dermal absorption and is composed of dimeric cupric tetracarboxylate then have the ability to bind to units with a short Cu-Cu internuclear separation acetylcholinesterase, thereby disrupting nervous and exhibits a unique turquoise-blue color. impulses and inhibiting the normal functions of MOF-199 was chosen for this research because it nerve cells1. Exploring novel and efficient ways contains open metal sites, which are necessary to to isolate or decontaminate OPs, with minimal achieve high storage capacities of gases such as environmental impact, has become a global hydrogen and methane, and is commercially necessity2. Using adsorbents and active available3, 9, 10, 11. The adsorption and compounds and immobilizing them on degradation performance of these composites nonwoven substrates are novel and promising was tested with methyl parathion. Methyl materials for the development of protective parathion was chosen as the test chemical clothing. The advantages of using a nonwoven because it also acts as a mimic for VX, which is substrate include breathability, low weight, and an organophosphate chemical warfare agent. high levels of comfort. Many active agents have Both 31P Solid State Nuclear Magnetic been incorporated into nonwoven nanofibrous Resonance (NMR) and Raman Spectroscopy mats to create materials that have the ability to were utilized to investigate the degradation of bind or detoxify chemical warfare agents and methyl parathion in the MOF-199 structure. pesticides. The problem presented with some of these technologies lies with the fact that in some cases the degradation products of OPs result in even more toxic substances. Isolating and containing the toxin and its degradation products from the environment is necessary to ensure safety. Creating a fabric that can keep the wearer safe, while maintaining a breathable and lightweight fabric, has become an important challenge. Aiming to meet this challenge, we have employed metal organic frameworks (MOFs) as an adsorbent and degradation agent. MOFs are crystalline nanoporous materials that consist of two main components, which are metal clusters that are held together by Figure 1. MOF-199 particles enmeshed in multifunctional organic linkers3, 4, 5. The reason electrospun polyacrylonitrile nanofibers.

RESULTS (2) Yang, Y. C.; Baker, J. A.; Ward, J. R. Chem. These composite fiber mats were shown to Rev. 1992, 92, 1729–1743. remove methyl parathion, an organophosphate (3) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; pesticide, more effectively as time increases and Wachter, J.; O'Keeffe, M.; Yaghi, O. M. were equally effective as the MOF-199 alone Science 2002, 295, 469–472. after two hours (Figure 2). This is proven by (4) Bordiga, S.; Regli, L.; Bonino, F.; Groppo, doing another ANOVA with just the specimens E.; Lamberti, C.; Xiao, B.; Wheatley, P. S.; reacted for 120 minutes. When comparing just Morris, R. E.; Zecchina, A. Phys. Chem. MOF and PAN/MOF-199 at 120 min, an Chem. Phys. 2007, 9, 2676-2685. ANOVA shows that these two specimen types (5) Prestipino, C.; Regli, L.; Vitillo, J. G.; are not significantly different from one another Bonino, F.; Damin, A.; Lamberti, C.; (F ratio =3.1876, Prob > F = 0.1487). This Zecchina, A.; Solari, P. L.; Kongshaug, K. shows that these fiber mats are an effective O.; Bordiga, S. Chem. Mater. 2006, 18, method for immobilizing MOF-199 particles 1337-1346. without severely hindering the adsorption (6) Britt, D.; Furukawa, H.; Wang, B.; Glover, T. performance of the particles themselves. G.; Yaghi, O. M. PNAS 2009, 106 (49), 20637-20640. Both 31P Solid State Nuclear Magnetic (7) Britt, D.; Tranchemontagne, D.; Yaghi, O.M. Resonance (NMR) and Raman Spectroscopy PNAS 2009, 105 (33), 11623-11627. demonstrated evidence of degradation of the (8) Furukawa, H.; Yaghi, O. M. J. Am. Chem. methyl parathion in the MOF-199 structure. Soc. 2009, 131, 8875-8883. (9) Rowsell, J. L. C.; Yaghi, O.M. Angew. Chem. Int. Ed. 2005, 44, 4670-4679. (10) Tranchemontagne, D. J.; Hunt, J. R.; Yaghi, O. M. Tetrahedron 2008, 64, 8553–8557. (11) Chui, S. S. Y.; Lo, S. M. F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. Science 1999, 283 (5405), 1148 – 1150.

Figure 2. Removed amount of methyl parathion (μg) vs. time (min) for three different specimen types, which include MOF-199 particles (black circles), composite PAN/MOF-199 electrospun fiber mats (white circles), and electrospun PAN fiber mats (black triangles).

CONCLUSIONS The method of making fiber mats that can adsorb methyl parathion could potentially work for other pesticides depending upon their solubility parameters. The fibers developed in this research may have applications that include protective clothing for agricultural workers or military personnel due to their observed adsorption properties and degradation capabilities.

REFERENCES (1) Banks, K. E.; Hunter, D. H.; Wachal, D. J. Environ. Int. 2005, 31, 351–356. Thermal and Comfort Measurements of Mattress Protectors Used for Prevention of Pressure Ulcers

Liliana Fontes1, Maria José Abreu1, Miguel Carvalho1, and Jorge Santos2 1University of Minho, Department of Textile Engineering; 2University of Minho, School of Psychology, Department of Basic Psychology, Centro Algoritmi and Centro de Computação Gráfica [email protected]

100% OBJECTIVE 80% cotton; A004 - polyuretha This work attempts to characterize several mattress 20% polyester protectors in terms of their ability to prevent Pressure ne 100% 100% Ulcers by testing their thermal and mechanical A005 100% cotton characteristics. polyester cotton 75% cotton; 100% A006 100% polyester 25% polyester PVC INTRODUCTION

Pressure Ulcers develop when there is excessive RESULTS AND DISCUSSION pressure on a bony prominence for a long period of Samples A001 and A005 showed the highest mass time, which may compress the tissue and blood per unit surface (approximately 700g/cm2) and vessels between the bone and the support surface. thickness (7-8mm), whereas samples A003 and A004 This compression, when prolonged, can cause where the ones with the lowest mass (between 100 ischemia, and eventually necrosis of the tissues. See and 150 g/cm2), and less than 1.5mm thick. Figure 1 for an example of the four stages of an ulcer.

It was found that only two samples were permeable to air – A001 and A005. This is explained by the fact that all the other textiles had an impermeable coating of PVC or polyurethane.

Figure 1 – Stages of a Pressure Ulcer As for draping properties, most samples showed a drape coefficient higher than 0.9, making them Pressure Ulcers show a high incidence and extremely stiff. The exceptions were samples A003 prevalence, are extremely costly to treat, and provoke and A004 (0.6). These results confirm the stiffness immense suffering for patients, who are at risk of test, in which we calculated flexural rigidity. dying from related complications, such as sepsis. KES was used to evaluate compression, tension and Pressure Ulcers are the result of a combination of shear. Only two samples were analyzed for their factors, with some of the most important being compressive properties. Results showed that sample pressure, temperature and humidity. The assessment A003 had the best recovery from compression (52%), of these properties in different textiles is a first but it was sample A004 that showed the best crucial step for the objective of a broader project: the compressibility (70%). development of textiles that aid in the prevention of Pressure Ulcers by redistributing pressure, reducing It was impossible to test sample A001 in both tensile temperature and managing humidity. and shear evaluation, due to its thickness. As for the other fabrics, it was found that tensile resilience APPROACH varied between 29% and 50% (A005 and A002, The characteristics of the six tested mattress respectively). Moreover, results indicated that all protectors are summarized in Table I. samples tended to be inelastic – the highest value was achieved by sample A004 (17%). Table I – Characteristics of all samples Code Fabric Filling Base Shear testing revealed that sample A002 had the 70% bamboo; 70% polyester; 100% highest shear stiffness. On the other end of the scale, A001 30% polyester 30% bamboo cotton samples A003 and A004 denoted the lowest stiffness. 100% Again, this appears to confirm both draping and A002 100% cotton 100% polyester polyuretha stiffness results. ne 100% Friction was determined using FricTorq. Again, it A003 100% cotton - polyuretha was not possible to test sample A001 due to its ne thickness. All samples showed similar values Table III – Evaluation of samples (approximately 0.2), with the exception of A004 Thermo Mechanic Humidity Struct. (0.3), making it the smoother fabric. This was A001 Good No data Good Excel. expected, given previous results of stiffness, drape A002 Good Fair Excellent Good and other mechanical properties. A003 Good Excel. Poor Fair A004 Excel. Excel. Excellent Fair The evaluation of thermal properties included testing A005 Excel. Poor Good Excel. with the Alambeta equipment and with a dry thermal A006 Excel. Fair Fair Good manikin. The Alambeta yields four relevant parameters: thermal conductivity (λ), diffusion (α), Sample A005 is extremely thick and has a low absorptivity (b) and resistance (r). Table II shows the coefficient of friction. Its thickness is expected to results obtained. absorb pressure from the user and distribute it across its surface, thereby delaying a situation where too Table II – Alambeta results much pressure would lead to the development of λ α b r Pressure Ulcers. Moreover, its low coefficient of (W/mºK) (m2/s) (W.s1/2/m2 (m2ºK/W) friction means that it is capable of sustaining the ºK) user’s body without the person sliding, which could A001 64.3 0.79 71.04 125.8 cause the skin to break down. However, sample A004 A002 48.62 0.62 61.8 114.4 showed opposite, less desirable results. A003 40.2 0.14 114.44 8.82 A004 36.98 0.53 52.62 37.94 Although sample A005’s mechanical properties are A005 52.18 0.41 82.62 135 not the best (high stiffness, low drapeability, inelastic and with a low recovery from mechanical forces), it A006 50.26 0.76 57.78 127.2 appears that this is a necessary trade-off in order to

have good results in other properties. In terms of To determine the thermal isolation of the fabrics we mechanical properties the best sample was by far used a thermal manikin on a constant temperature A004. program, and employed the parallel method for determining isolation. Results showed small Finally, sample A005’s thermal properties were fairly differences between samples, with values varying good – excellent water absorbency, reasonably good between 0.6 and 0.8 Clo (samples A002 and A006, wicking capability and excellent thermal isolation. respectively). These results indicate that all mattress On the other hand, sample A004 did not absorb water protectors have good thermal properties, but sample and had poorer thermal isolation, although it did A006 is the best at keeping the body’s temperature show the best wicking capacity. constant.

In sum, these results suggest that samples A004 and Finally, we tested the protectors for their ability to A005 perform best for the purposes of preventing wick water vertically. Results showed that all Pressure Ulcers. Therefore, future work will focus on samples have similar wicking abilities in both how to best apply them in a clinical setting. directions, with the exception of sample A006, which only wicks water in the direction of the warp. Sample FUTURE WORK A003 showed the slowest wicking velocity Future work will focus on conducting water-vapor (approximately 0.05cm/min), whereas sample A004 permeability tests and on analyzing the protector’s was the fastest – approximately 0.5cm/min. capacity to manage and distribute pressure. This will Moreover, it was found that samples A004 and A002 be accomplished by using a pressure-sensing mat in achieved the highest height in water wicking – conjunction with the thermal manikin. approximately 5cm.

ACKNOWLEDGMENT CONCLUSIONS This work was supported by FCT with the grant All these results combined appear to indicate that SFRH/BD/79762/2011. samples A004 and A005 would be the best choices for the prevention of Pressure Ulcers. Table III shows REFERENCE a qualitative evaluation of all samples tested. Theaker, C. (2003). “Pressure sore prevention in the

critically ill: what you don’t know, what you should

know and why it’s important.” Intensive and Critical

Care Nursing, 19 163–168.

The Influence of Copper (II) Ions on Wool Photostability in the Dry State

Hu Zhang1, Santanu Deb-Choudhury1, Jeffrey Plowman1, Keith Millington2 and Jolon Dyer1 1AgResearch, Proteins & Biomaterials, Lincoln Research Centre, Christchurch, New Zealand 2CSIRO Materials Science and Engineering, Belmont, VIC 3216 Australia [email protected]

ABSTRACT in the dry state. Vis/near infrared reflectance spectra, The metal ion content of wool is of significance both tryptophan-type fluorescence (λEx=295 nm, λEm=340 to its biological growth and to subsequent post-harvest nm) and photo-induced chemiluminescence (PICL) properties of wool textiles [1-3]. The formation of free emissions of natural wool and copper (II) treated radicals catalyzed by trace metal elements of wool, wool were obtained and contrasted. Changes of CIE especially copper and iron, has been proposed to be a whiteness of wool treated with copper (II) solution key mechanism contributing to the photoyellowing of indicate that under blue light irradiation it wool, particularly in the wet state. Nevertheless, there photobleached at a relatively similar rate has been little research on the influence of these independent of the amount of bound copper ions metals on wool discoloration in the dry state [4-6]. (Figure 1), whereas D1925 yellowness indices indicate that at a higher concentration it yellowed faster and experienced greater overall color changes under UVA and UVB irradiation (Figure 2). In addition, binding copper ions to wool caused a decrease in tryptophan-type fluorescence and PICL emissions relative to controls.

Using proteomic techniques, our future studies will investigate the molecular process of the photoyellowing of wool, in particular tryptophan and tyrosine residues, in the presence of known Figure 1: Changes of CIE whiteness of natural wool amounts of copper (II) ions. and treated wool under blue light irradiation ACKNOWLEDGMENT This work is financially supported by a Wool Research Organisation of New Zealand Inc and New Zealand Wool Industry Charitable Trust Postdoctoral Fellowship.

REFERENCES 1. J Court, J W Ware and S Hides, Sheep Farming for Meat & Wool (Collingwood, CSIRO Publishing, 2010 ) 66. 2. P I Hynd and D G Master, in Nutrition and Figure 2: Changes of yellowness of natural wool and Wool Growth , Eds M Freer and H Dove treated wool under UVB and UVA irradiation (Collingwood, CSIRO Publishing, 2002) 174. 3. G E Rogers, Exp. Dermatol., 15 (2006) 931. In this study, wool fabric samples were treated with 4. K R Millington, Color. Technol., 122 (2006) 0.05M, 0.01 M and 0.1 M Cu(ClO ) solutions. 301. 4 2 5. K R Millington, L.J. Kirschenbaum, Color Treatment with 0.1M KClO4 solution was used as a - Technol., 118 (2002) 6. control to take into account any influence of ClO4 anion on the wool photodiscoloration. The relative 6. G J Smith, J. Photoch.Photobio. B, 27 (1995) photodiscoloration of copper (II) treated wool was 187. examined under UVA, UVB and blue light irradiation Open-Architecture Composite Tube: Design and Manufacture

David Branscomb1, Austin Gurley2, David Beale3, Roy Broughton3 1PhD Candidate 2Undergraduate Research Assistant 3Faculty Advisor Department of Polymer and Fiber Engineering Auburn University, Auburn, Alabama, USA

INTRODUCTION RESULTS In designing components of structural systems, truss Table I shows the initial target steel drive shaft geometries are often utilized to minimize weight and properties along with the predicted properties of the maintain strength and stiffness. We have applied this two composite tubes. approach to cylindrical composite components of power transmission devices – drive shafts, etc. While Table I Mechanical Properties and Targets thin walled tubes theoretically have sufficient strength to transmit torque, complex loads induced by Reference Analysis Input/ Target Output 5.Carbon even slight misalignment and centrifugal forces can 1. 2. Standard 3.Composite 4.Optimization Open Properties Driveshaft Tube Starting Point precipitate large bending deformations - a particular Structure problem at high rotational speeds. Resistance to Material 4130 Carbon Fiber Carbon buckling (and bending) requires out-of plane Steel Fabric Fiber Yarn Length stiffness, which is difficult to obtain in light-weight 431.8 431.8 431.8 (mm) (thin-walled) cylindrical structures [1-3]. This work Outer is directed toward the design, manufacture and Diameter 15.88 61.14 60.96 60.96 analysis of lightweight, cylindrical composite (mm) structures having high resistance to buckling. Inner Diameter 9.5 60.33 54.61 54.61 (mm) APPROACH Weight (g) 1120.37 260.82 2085.16 280.09 The following is a list of the steps used in the design Weight {reference} 77% N/A 75% and construction of a composite drive shaft: Reduction 1. Properties of a steel drive shaft were used as a Target Stiffness 1005.2 1510.1 N/A 1510.1 benchmark (Table I). (Nm/rad) 2. A CAD-based, topological-optimization design process was used to develop an open architecture Figure 1 is a schematic of the design process. composite tube. A target of 75% weight reduction and 50% increase in torsional stiffness was selected (Figure 1 and Table I). 3. Large diameter yarn/tow structures were fabricated from 12 3-K carbon prepreg yarns in the core of an overbraid and after curing, their mechanical properties were measured (Table II). 4. A CAD/FEA model (Figure 4) was constructed similar to the topological optimization but using the yarn structures and properties derived from 3 (above). FEA was used to predict the properties Figure 1. CAD Based Optimization Design Process of the future drive shaft construction. 5. A composite preform drive shaft was produced on Figure 2 shows the starting point for topological optimization. Figure 3 shows the truss like structure a Maypole braiding machine using the large carbon prepreg yarns of 3 (above), and following at the end point of the topological optimization. the CAD optimization of 2 as closely as possible (shown in Figure 5). 6. A similar weight composite tube was made from a thin, full cover cylindrical braided tube, via wet layup (Shown in Figure 6). 7. The composite drive shaft was cured and tested. 8. The test results were compared with the predicted Figure 2. Initial tube with “seed” holes mechanical properties from 4 (Figure 7). CONCLUSIONS We have developed a light weight open-structure composite tube for transmitting torque. A design methodology based on shape optimization and finite element analysis is presented to predict the ideal shape of an open-architecture composite tube used as Figure 3. Shape optimized surfaces of tube a drive shaft. Design goals are made and certain features are input to a topological optimization Figure 4 shows the CAD model superimposed on the algorithm. The results of the optimization are altered optimized surfaces. from their triangulation form into a solid model by recognition of patterns in the optimized shape. A robust large yarn suitable for braiding open- architecture composites has been formed by consolidating pre-impregnated tows. With this yarn a Maypole braiding machine is used to manufacture the Figure 4. CAD model and shape optimized surfaces open-architecture composite tube. A solid full Table II shows the measured properties for the cured, coverage composite tube of similar weight and major 36 K- filament prepreg yarns with overbraid. dimensions is also manufactured and compared. The open-architecture composite tube is less stiff in Table II Measured properties of large composite yarn torsion but is observed to be stiffer in the radial and longitudinal directions. We have shown a design Tensile Tensile Percent Weight/Length of process which may be applied to future open Strength Modulus Elongation Pre-impregnated Yarn structure geometries in general. Using the method presented, geometries may be found whose properties 2.17 GPa 149.62 GPa 1.3 % 3.37 g/m in certain loading conditions will surpass those of metallic and full-coverage composite alternatives. Figures 5 and 6 are photographs of the open structure and full cover factor braided tube composites REFERENCES (respectively) produced on a Maypole braiding [1] E.R. Lancaster, C.R. Calladine and S.C. Palmer, machine. Figure 7 shows how these two composite Paradoxical buckling behavior of a thin cylindrical tubes respond to applied torque. shell under axial compression. International Journal of Mechanical Sciences, 42, 843–865, 2000. [2] von Kármán Th, Dunn LG, Tsien HS. The influence of curvature on the buckling characteristics of structures. Journal of Aeronautical Sciences

Figure 5. Photo of open architecture composite 1940;7:276–81. [3] Pircher, M., Bridge, R., “Buckling Of Thin- Walled Silos And Tanks Under Axial Load—Some New Aspects”, Journal Of Structural Engineering, October 2001, pp. 1129 – 1136.

Figure 6. Photo of full coverage composite tube ACKNOWLEGMENTS The authors would like to acknowledge the Auburn Office of University Scholars Spirit of Auburn Presidential Scholarship, Alabama Space Grant Consortium NASA Training Grant #NNG05GE80H, TCR Composites, and AU Department of PFEN, Dr. Stephen Bigbee, Hayes Johnson, and Jonathan Hebert for their contributions to this project.

Figure 7. Results of torsion physical testing and FEA

We Gratefully Acknowledge Our

SPONSORS

Fiber Society Officers 2012

• President Cheryl Gomes, QinetiQ North America, Inc.

• Vice-President Rudolf Hufenus, Empa

• Secretary Michael Ellison, Clemson University

• Treasurer Stephen Michielsen, North Carolina State University

Fiber Society Governing Council 2012

• Ian R. Hardin, Past-President (2011), University of Georgia

• Janice R. Gerde, Department of Homeland Security

• Gang Sun, University of California, Davis

• Xungai Wang, Deakin University

• Glen Simmonds, DuPont

• Konstantin Kornev, Clemson University

• Gregory Rutledge, Massachusetts Institute of Technology

• Michael Jaffe, New Jersey Institute of Technology