Volume 4, Issue 1, Summer 2004

Application of for high performance

Lei Qian Institute of Technology College of Textiles North Carolina State University

Juan P. Hinestroza TECS, College of Textiles North Carolina State University

ABSTRACT

This paper summarizes the recent development of nanotechnology in textile areas including textile formation and textile . Details on two major technical aspects, using nanosize entities and employing specific techniques to create nanosize structure inside textile materials, have been elucidated. A number of nanosize fillers and their resultant performances have been reviewed. Particularly, nanolayer assembly, a new concept of textile surface coating, has been introduced. At the end, perspectives regarding future development of nanotechnology for smart and intelligent textiles have been addressed.

Keywords: Nanotechnology, nanosize fillers, nanosize structure, , cellular structure

Introduction nanosize particles in a precise and controlled manner in order to build materials with a Nanotechnology is an emerging fundamentally new organization and novel interdisciplinary technology that has been properties. The embryo of nanotechnology is booming in many areas during the recent “atomic assembly”, which was first publicly decade, including , articulated in 1959 by physicist Richard mechanics, electronics, optics, medicine, Feynman. Nanotechnology is called a plastics, energy, electronics, and aerospace. “bottom up” technology by which bulk Its profound societal impact has been materials can be built precisely in tiny considered as the huge momentum to usher building blocks, different from the in a second industrial revolution.1,2 traditional manufacture ― “top down” technology. Therefore, resultant materials The “nano” in nanotechnolgy comes have fewer defects and higher quality. from the Greek word “nanos” that means dwarf. Scientists use this prefix to indicate The fundamentals of nanotechnology lie 10-9 or one-billionth. One nanometer is one- in the fact that properties of substances billionth meter that is about 100,000 times dramatically change when their size is smaller than the diameter of a single human reduced to the nanometer range. When a hair. Nanotechnology endeavors are aimed bulk material is divided into small size at manipulating atoms, molecules and particles with one or more dimension Article Designation: Scholarly 1 JTATM Volume 4, Issue 1,Summer 2004 (length, width, or thickness) in the The main function of nanosize fillers is nanometer range or even smaller, the to increase the mechanical strength and individual particles exhibit unexpected improve the physical properties such as properties, different from those of the bulk conductivity and antistatic behaviors. Due material. It is known that atoms and to their large surface area, these nanofillers molecules possess totally different behaviors have a better interaction with polymer than those of bulk materials; while the matrices. Being in the nanometer range, the properties of the former are described by fillers might interfere with polymer chain quantum mechanics, the properties of the movement and thus reduce the chain latter are governed by classic mechanics. mobility. Being evenly distributed in Between these two distinct domains, the polymer matrices, nanoparticles can carry nanometer range is a murky threshold for load and increase the toughness and abrasion the transition of a material’s behavior. For resistance; nanofibers can transfer stress example, ceramics, which normally are away from polymer matrices and enhance brittle, can easily be made deformable when tensile strength of composite fibers. their grain size is reduced to the low Additional physical and chemical nanometer range. A gold particle of 1 nm performances imparted to composite fibers across shows red . Moreover, a small vary with specific properties of the amount of nanosize species can interfere nanofillers used. Distribution of nanofillers with matrix polymer that is usually in the in polymer matrices through mechanical and similar size range, bringing up the chemical approaches is one of the important performance of resultant system to an aspects leading to high quality of unprecedented level. These are the reasons nanostructured composite fibers. Although why nanotechnology has attracted large some of the filler particles such as clay, amounts of federal funding, research activity metal oxides, carbon black have previously and media attention. been used as microfillers in composite materials for decades, reducing their size The textile industry has already impacted into nanometer range have resulted in higher by nanotechnology. Research involving performances and generated new market nanotechnology to improve performances or interest. to create unprecedented functions of textile materials are flourishing. These research Carbon Nanofibers and Carbon endeavors are mainly focused on using Nanoparticles nanosize substances and generating nanostructures during manufacturing and Carbon nanofibers and carbon black finishing processes. nanoparticles are among the most commonly used nanosize filling materials3,4. Carbon Nanotechology in Manufacturing nanofibers can effectively increase the Composite Fibers tensile strength of composite fibers due to its high aspect ratio, while carbon black Nano-structured composite fibers are in nanoparticles can improve their abrasion the area where we see the early blooming of resistance and toughness. Both of them have nanotechnology, while many other high chemical resistance and electric applications are still way off future. Those conductivity. Several fiber-forming composite fibers employ nanosize fillers polymers used as matrices have been such as nanoparticles (clay, metal oxides, investigated including , and carbon black), graphite nanofibers (GNF) polyethylene with the weight of the filler and carbon nanotubes (CNT). Besides, from 5% to 20%5,6. nano-structured composite fibers can be generated through foam-forming process, other than using nanosize fillers.

Article Designation: Scholarly 2 JTATM Volume 4, Issue 1,Summer 2004 into polyproprene before it is extruded. As a result, polyproprene with clay nanoparticles by weight percentage of 5% can be colored Clay Nanoparticles by acid dyes and disperse dyes.9

Clay nanoparticles or nanoflakes are Metal Oxide Nanoparticles composed of several types of hydrous aluminosilicates. Each type differs in Nanosize particles of TiO2, Al2O3, ZnO, chemical composition and crystal structure. and MgO are a group of metal oxides that Clay nanoparticles possess electrical, heat possess photocatalytic ability, electrical and chemical resistance and an ability of conductivity, UV absorption and photo- blocking UV light. Therefore, composite oxidizing capacity against chemical and fibers reinforced with clay nanoparticles biological species. Intensive researches exhibit , anti-UV and anti- involving the nanoparticles of metal oxides corrosive behaviors. For example, have been focusing on , self- nanoparticles of montmorillonite, one of decontaminating and UV blocking functions most commonly used clay, have been for both military protection gears and applied as UV blocker in nylon composite civilian products 6. Nylon fiber filled fiber. The mechanical properties with a clay with ZnO nanoparticles can provide UV mass fraction of only 5 % exhibits a 40% shielding function and reducing static higher tensile strength, 68% greater tensile electricity of nylon fiber. A composite fiber with of TiO2/ MgO can provide self-sterilizing function 18.

Carbon Nanotubes

Carbon nanotube (CNT) is one of the most promising building blocks existing. Its higher strength and high electrical conductivity are not comparable by carbon nanofibers. CNT consists of tiny shell(s) of graphite rolled up into a cylinder(s). With 100 times the tensile strength of steel at one- sixth weight, thermal conductivity better than all but the purest , and modulus, 60% higher flexural strength, and electrical conductivity similar to copper, but a 126% increased flexural modulus7. In with the ability to carry much higher addition, the heat distortion temperature currents, CNT seems to be a wonder (HDT) increased from 65oC to 152oC. material. Nanosize clay flakes are arranged densely and alternately than the therefore, the Generally, CNTs are classified into has barrier performance single-walled (SWNT) and to , chemicals or other harmful multi-walled carbon nanotube (MWNT). species.7,8 They are usually made by carbon-arc discharge, laser ablation of carbon, or Another function of clay nanoparticles is chemical vapor deposition. The potential to introduce dye-attracting sites and creating applications of CNTs include conductive dye-holding space in polyproprene fibers, and high-strength composite fibers, energy storage and energy conversion devices, known as non-dyeable fiber due to its 10,11 structural compactness and lack of dye- sensors, and field emission displays. attracting sites. Nanoparticles of montmorillonite are modified with One of the successful examples of CNT quaternary ammonium salt and then mixed composite fiber is the SWNT- polyvinyl Article Designation: Scholarly 3 JTATM Volume 4, Issue 1,Summer 2004 alcohol fiber with fiber diameters in One of the approaches is to make use of micrometer range produced by using a thermodynamic instability to produce nano- coagulation-based spinning process. The cellular materials. Controlled dosing of fiber exhibits twice the stiffness and supercritical CO2 is used to tailor the strength, and 20 times the toughness of steel of a polymer melt. The domains of wire of the same weight and length. CO2 embedded in the polymer melt expand Moreover, the fiber toughness can be four in volume when the pressure applied to the times higher than that of spider silk and 17 system is suddenly reduced. These times greater of fibers used in nanobubbles are then permanently entrapped bulletproof vests.10 Therefore, this type of in the polymer when the temperature falls fibers has potential applications in safety below the solidifying temperature of the harnesses, explosion-proof blankets, and polymer matrix. The porosity of the final electromagnetic shielding. Continuing composite can be in the range of 10-20nm. research activities on CNT fibers involve In order to keep the pore size within study of different fiber polymer matrices nanometer range, a great effort is made in such as polymethylmethacrylate (PMMA) controlling the thermodynamics of the foam- and polyacrylonitrile (PNA) as well as CNT forming process. The resultant nanocellular dispersion and orientation in polymers. fibers can be used as high-performance Processing approaches such as wet spinning, composite fibers as well as for sporting and melt spinning and electron spinning were aerospace materials. extensively explored.12,13,14 Nanotechnology in Textile Finishing Nanocellular Foam Structures The in the Using nanosize fillers is one of the most textile finishing area has brought up common approaches to create innovative finishes as well as new nanostructured composite fibers. Another application technique. Particular attention approach is to generate nanosize cellular has been paid in making chemical finishing structures in polymer matrices.15 more controllable and more thorough. Ideally, discrete molecules or nanoparticles of finishes can be brought individually to designated sites on textile materials in a specific orientation and trajectory through thermodynamic, electrostatic or other technical approaches.

Upgrade of Chemical Finishes and Resultant Functions

Nanotechnology not only has exerted its influence in making versatile fiber composites but also has had impact in making upgraded chemical finishes. One of A certain amount of nanosize porosity in the trends in synthesis process is to pursue a material results in attributes such as nanoscale emulsification, through which lightweight, good , high finishes can be applied to textile material in cracking resistance without sacrificing in a more thorough, even and precise manner. mechanical strength. A potential application Finishes can be emulsified into nano- of cellular structure is to encapsulate micelles, made into nano-sols or wrapped in functional components inside of nanosize nanocapsules that can adhere to textile cells. substrates more evenly. These advanced finishes set up an unprecedented level of textile performances of stain-resistant,

Article Designation: Scholarly 4 JTATM Volume 4, Issue 1,Summer 2004 hydrophilic, anti-static, wrinkle resistant and One of the technical approaches is to use shrink proof abilities.16 electrostatic attraction to self-assemble nanolayer coatings on textile materials for protective and self-healing function. The electrostatic approach is particularly Nanoparticles in Finishing appealing as the thickness, homogeneity and sequence of these nanolayers can be Nanoparticles such as metal oxides and precisely controlled by control of molecular ceramics are also used in textile finishing to architecture, self-assembly and electrostatic alter surface properties and impart textile interactions.20-23 In addition, the self-healing functions.17 Nanosize particles have a larger capability makes this technique particularly surface area and hence higher efficiency tolerant to defects. 24 than larger size particles. Besides, nanosize particles are transparent, and do not blur color and brightness of the textile substrates. However, preventing nanoparticles from aggregation is the key to achieve a desired performance.

As an example, the fabric treated with nanoparticles TiO2 and MgO replaces fabrics with active carbon, previously used as chemical and biological protective materials. The photocatalytic activity of TiO2 and MgO nanoparticles can break harmful and toxic chemicals and biological agents. These nanoparticles can be pre- engineered to adhere to textile substrates by The self-assembly process begins by using spray coating or electrostatic 18 exposing a charged surface to a solution of methods. Finishing with nanoparticles can an oppositely charged polyelectrolyte. The convert fabrics into sensor-based materials. amount of adsorbed material is self-limiting If nanocrystalline piezoceramic particles are by the charge density of the substrate21. incorporated into fabrics, the finished fabric Surplus polymer solution adhering to the can convert exerted mechanical forces into support is removed by simply washing it in a electrical signals enabling the monitoring of neutral solution. Under the proper bodily functions such as heart rhythm and 19 conditions, the polyion is adsorbed with pulse if they are worn next to skin. more than the stoichiometric number of charges relative to the substrate, reversing Self assembled Nanolayers the sign of the surface charge. In consequence, when the substrate is exposed Self-assembled nanolayer (SAN) coating to a second solution containing a polyion of is a challenge to traditional textile coating. opposite charge, an additional polyion layer Research in this area is still in embryo stage. is adsorbed reversing in this way the sign of In self-assembled nanolayer (SAN) coating, the surface charge once again. Consecutive target chemical molecules form a layer of cycles with alternating adsorption of thickness less than nanometer on the surface polyanions and polycations result in step- of textile materials. Additional layers can be wise growth in total thickness of polymer added on the top of the existing ones films25. creating a nanolayered structure. Different SAN approaches are being explored to The fundamentals of the electrostatic confer special functions to textile materials. self-assembly are more complicated than they appeared to be.26 Although this technique is based on the electrostatic Article Designation: Scholarly 5 JTATM Volume 4, Issue 1,Summer 2004 attraction between positively and negatively horizon of textile materials under this charged species, the interaction between irresistible technology wave. these charged species is specific to the nature of the substrate and that of the References polyelectrolytes.23,27 Polyelectrolyte adsorption is nearly irreversible, so the built- 1. Cover story, , A Big up films do not represent equilibrium Market Potential, Chemical Week, structures. This behavior adds to the October 16, 2002, p17 versatility of the method, but implies that a 2. David R. Forrest, The Future Impact close kinetic control of the adsorption of Molecular Nanotechnology on process is required in order to control film Textile Technology and on the thickness and growth. The electrostatic self- Textile Industry, Copyright 1996, assembly may depend on factors controlling David R. Forrest and the Industrial the entropy of the polymer chains, such as Fabrics Association International, molar mass, flexibility of the chains, ion http://www.salsgiver.com/people/for exchange capacity as well as the rest/IFAI_text.html hydrophobic interactions, charge transfer 3. Harholdt, K., Carbon Fiber, Past and interactions, π-π stacking forces, and Future, Industrial Fabric Products hydrogen bonding.28 No single theory is Review, Vol 88, No 4, 2003, p14 available that can provide a complete 4. Xu C., Agari Y. and Matsuo M., description of the self-assembly process; Mechanical and Electric Properties moreover, deeper understanding of the of Ultra-High-Molecular Weight specificity of ion-ion and ion-substrate Polyethylene and Carbon Black interactions on surface of textile materials Particle Blends, Polymer Journal, with complicated contour remains a 30, No 5, 1998, p372 challenge.29,30,31,32 5. Chen J. and Tsubokawa N., Electric Properties of Conducting Composite Future Prospect from Poly(ethylene oxide) and Poly(ethylene oxide)-Grafted Caron Future developments of Black in Solvent Vapor, Polymer in textiles will have a two- Journal, 32, No 9, 2000, p729 fold focus: 1) upgrading existing functions 6. (a) Kim Y. K. Lewis A. F. et al., and performances of textile materials; 2) Nanocomposite Fibers, National developing smart and intelligent textiles Textile Center Annual Report M00- with unprecedented functions. The latter is D08, 2002 (b) more urgent from the standpoint of http://www.nanophase.com/applicati homeland security and advancement of ons/ technology. The new functions with textiles 7. (a)http://fire.nist.gov/bfrlpubs/fire99 to be developed include 1) wearable solar /art164.html cell and energy storage; 2) sensors and (b)http://www.ccmr.cornell.edu/~gi information acquisition and transfer; 3) anellis/research/silicates.html multiple and sophisticated protection and 8. Tassinari T. H. and Auerbach M., detection; 4) health-care and wound healing Nonwovens for Military Combat functions; 5) self-cleaning and repairing Systems, The International functions. Nonwovens conference and Exposition, 2001 Undoubtedly, Nanotechnology holds an 9. Qinguo Fan, Samuel C. Alton R. enormously promising future for textiles. It Wilson, et al., nanoclay-Modified is estimated that nanotechnology will bring Dyeable with Acid about hundreds of billions dollars of market and Disperse Dyes, AATCC review, impact on new materials within a decade; June 2003, p25 textile certainly has an important share in 10. (a) Ray H. Baughman, Anvar A. this material market. We expect to see a new Zakhidov, and Walt A. de Heer, Article Designation: Scholarly 6 JTATM Volume 4, Issue 1,Summer 2004 Carbon Nanotubes ― the Route s/PDF/2001/cr/NASA-2001- Toward Applications, Science, Vol cr211265.pdf 297, 2, August 2002, p787 (c)http://www.empa.ch/plugin/templ (b)http://www.smalltimes.com/docu ate/empa/225/21999/--- ment_display.cfm?document_id=62 /l=2/changeLang=true/lartid=21999/ 04 orga=/type=/theme=/bestellbar=/ne 11. Apparao M. Rao, Rodney Andres w_abt= and Frank Derbyshire, Nanotube 20. Decher, G.; Lvov, Y.; Schmitt, J. Composite , Energeia, Thin Solid Films 1994, 244, 772- Vol 9, No 6, 1998, p1 777. 12. M. Sennett, E. 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Colloids 2002, Milwaukee, WI (b) Frank K. and Surfaces A: Physicochemical Ko, Sakina Khan, et al., Structure and Aspects 1999, 146, and Properties of Carbon Nanotube 337-346. Reinforced Nanocomposites, AIAA 27. Park, S. Y.; Rubner, M. F.; Mayes, 2002-1426 A. M. Langmuir 2002, 18, 9600- 15. Hilyard N.C. and Cunningham A., 9604. Low Density Cellular Plastics, 28. Delcorte, A.; Bertrand, P.; Arys, Chapman & Hall, London, UK, X.; Jonas, A.; Wischerhoff, E.; 1994 Mayer, B.; Laschewsky, A. Surface 16. http://textileinfo.com/en/tech/nanote Science 1996, 366, 149-165. x/page02.html 29. Ninham, B. W.; Kurihara, K.; 17. David S. Soane, Nanoparticle-based Vinogradova, O. I. Colloids and permanent treatments for textiles, Surfaces, A: Physicochemical and United State Patent, No 6,607, 994, Engineering Aspects 1997, 123-124, 2003 7-12. 18. Scott M. Hartley and holly Axtell, 30. Fogden, A.; Ninham, B. W. The Next Generation of Chemical Advances in Colloid and Interface and Biological Protective Material Science 1999, 83, 85-110. Utilizing Reactive Nanoparticles, 31. Decher, G. ACS Symposium Series Gentex Corporation, Carbondale, 1997, 672, 445-459. PA 18407 32. Lvov, Y.; Price, R.; Gaber, B.; 19. (a) Ward D, Small-Scale Ichinose, I. Colloids and Surfaces Technology with the Promise of Big A: Physicochemical and Rewards, Technical Textiles Engineering Aspects 2002, 198-200, International, 12, No 2, 2003, p13 375-382. (b)http://techreports.larc.nasa.gov/ltr Article Designation: Scholarly 7 JTATM Volume 4, Issue 1,Summer 2004