Thermosetting Resins 2018 Conference

PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE

25 – 27 SEPTEMBER 2018 BERLIN, GERMANY

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ISBN: 978-3-00-060827-8

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PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

THERMOSETTING RESINS 2018

FROM BASICS TO APPLICATIONS

INTERNATIONAL CONFERENCE

25 – 27 SEPTEMBER 2018 BERLIN, GERMANY

3 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

CONFERENCE BOARD

Prof. Dr. Monika Bauer InnoMat GmbH, Teltow, Germany

Prof. Dr. Jean-François Gérard University of Lyon, National Institute of Applied Sciences (INSA), IMP UMR CNRS 5223, Villeurbanne, France

Dr. Terry McGrail University of Limerick, Irish Composites Centre (IComp), Limerick, Ireland

4 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

SCIENTIFIC COMMITTEE

Prof. Dr. Alexander Bismarck Polymer and Composite Engineering (PaCE) group, Department of Material Chemistry, University of Vienna (Vienna, Austria)

Prof. Dr. Alex Dommann Department „Materials meet Life“, Empa – Swiss Federal Laboratories for Materials Science and Technology (St. Gallen, Switzerland)

Prof. Dr. Jannick Duchet-Rumeau University of Lyon, National Institute of Applied Sciences (INSA), IMP (Villeurbanne, France)

Dr. Jocelyne Galy University of Lyon, National Institute of Applied Sciences (INSA), IMP (Villeurbanne, France)

Prof. Dr. Reinhard Lorenz Department of Chemical Engineering, University of Applied Sciences Muenster (Muenster, Germany)

Prof. Dr. Dennis W. Smith Department of Chemistry and Marvin B. Dow Advanced Composites Institute, Mississippi State University (Mississippi State, MI, USA)

Dr. Ambrose Taylor Faculty of Engineering, Department of Mechanical Engineering, Imperial College London (London, United Kingdom)

Prof. Dr. Brigitte Voit Leibniz Institute of Polymer Research Dresden IPF (Dresden, Germany)

5 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

THANK YOU FOR SPONSORING!

6 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

CONTENT

PLENARY LECTURES ...... 13 Trends in high performance thermosetting resins ...... 14 Zoubair Cherkaoui ...... 14 Future challenges for aerospace composites ...... 15 David Tilbrook...... 15 The solidification rheology of amorphous polymers –Vitrification as compared to gelation .. 18 H. Henning Winter ...... 18 Vitrimers: Upcoming recyclable and reshapable thermosets ...... 20 Filip Du Prez ...... 20 Silicone resins –An emerging class of binders for fiber reinforced composites? ...... 21 Detlev Ostendorf1, Torsten Gottschalk-Gaudig2, Christoph Uhlig3, Olaf Kahle3, Jörg Bauer4 ...... 21 Developing and modeling thermosetting adhesives for composite and multi -material joints.. 25 Sascha Pöller & Tim Welters ...... 25

SESSION 1: CHEMISTRY ...... 28 Advanced polymer networks from fluoroalkenes and enediynes ...... 29 Ketki Shelar, Karl Mubeka, Eugene Cardona, Ganesh Narayanan, Behzad Farajidizaji, Andrzej Sygula, Charles Pittman, Dennis W. Smith, Jr...... 29 High Tg thermoplastic-modified bismaleimide matrices and related composite materials - Fracture mechanics ...... 30 Jean-Francois Gérard, Guillaume Fischer, Frédéric Lortie, Matteo Ciccotti1 ...... 30 A new class of fast curing high performance UP-resins yielding thermosets with significantly improved thermal properties ...... 31 Reinhard Lorenz ...... 31 Amphiphilic block copolymers based on chain-extended polyester – Role of compatibility and reactive groups ...... 32 Jan-Pierre Schneider1, Berthold Just1, Manfred Döring2 ...... 32

SESSION 2: MODELING & CHARACZERIZATION ...... 36 Ab initio design of binders architecture and optimization of curing conditions for cross -linked polyurethane/polyurea coatings ...... 37 Miroslava Dušková-Smrčková, Karel Dušek ...... 37 Modeling polymer nanocomposites of bio-sourced thermoset resins and carbon nanotubes ... 38 Shamil Saiev,1 Leïla Bonnaud,2 Ludovic Dumas,1 Tao Zhan ,1 Philippe Dubois,1,2 ...... 38 David Beljonne,1 Roberto Lazzaroni1,2 ...... 38 Design of functional interfaces in carbon fiber based composite materials ...... 42 Jannick Duchet-Rumeau, Vincent Lutz, Wenyong Zhang, Frédéric Lortie, Jean-François Gérard ...... 42 Non-crimp glass fibre/thermoplastic composites with functional surface properties ...... 46 Angeliki Chanteli, Rachel Kennedy, Terry McGrail, Walter Stanley ...... 46

SESSION 3: GREEN CHEMISTRY ...... 50 Isocyanate-free routes to multifunctional bio-based polyhydroxyurethane thermosets and composites ...... 51 Hannes Blattmann, Stanislaus Schmidt, Vitalij Schimpf, Burkhardt Pössel, Rolf Mülhaupt ...... 51

7 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

Isosorbide as a building block for thermosetting resins ...... 54 Jean-Pierre Pascault1,2, Françoise Mechin1,2, Etienne Fleury 1,2, Héloise Blache1,2, Senén Paz3, Clothilde Buffe4, Audrey Sahut4, René Saint-Loup4 ...... 54 High-performance recyclable thermosets from lignin derivative vanillin ...... 57 Songqi Ma ...... 57 Original route for tuning biobased oligoesters structures as thermoset precursors ...... 58 Jocelyn Clénet, Emmanuelle Richely, Mélanie Fissiaux, Daniel Portinha, Etienne Fleury ...... 58

SESSION 4: CHARACTERIZATION METHODS ...... 61 X-ray analytical methods to understand polymer functionality ...... 62 Anjani Maurya1, Amin Sadeghpour1, René M. Rossi1, Sara Dalle Vacche2, Yves Leterrier2, Alex Dommann1, Antonia Neels1 ...... 62 AFM-IR insights into epoxy resin nanostructures ...... 63 Suzanne Morsch...... 63 A novel sensor platform for thermal property measurements of thermosetting resins using the three-omega method ...... 67 Corinna Grosse1, Mohamad Abo Ras1, Karim Elabshihy1, Daniel May1,2, Yvonne Chowdhury3, ...... 67 Monika Bauer3, Aapo Varpula4, Kestutis Grigoras4, Mika Prunnila4, Bernhard Wunderle2...... 67 Cryomilling: A critical step for accurate determination of degree of cure and resin content in carbon fibre reinforced thermosetting composites ...... 71 Nessa Fereshteh Saniee, Neil Reynolds, Ken Kendall ...... 71

SESSION 5: (GREEN) CHEMISTRY ...... 74 Crosslinking mechanisms and kinetics of an innovative formaldehyde -free resole, for aerospace applications ...... 75 Lérys Granado1, Romain Tavernier1, Gabriel Foyer2, Ghislain David1, Sylvain Caillol1 ...... 75 Bio-based epoxy resin systems as potential alternatives to petroleum-based epoxy matrices in marine fibre-reinforced polymer composites ...... 77 Niamh H. Nash1, Lorcan Egan2, Carlos Bachour1, Ioannis Manolakis1, Anthony J. Comer1,2 ...... 77 Polybenzoxazine technology for lightweight and high-performance composites ...... 83 Leïla Bonnaud1, Oltea Murariu1,2, Philippe Dubois1,2, Virginie Canart3, Frederik Goethals3, Lies Willaert4, Chung-Hae Park5 ...... 83 Novel latent hardeners and catalysts for epoxy resins ...... 84 Alessandro Napoli, Kenneth B. Scobbie, Susanne Elmer, Ebrahim Farmand Ashtiani, Florian Klunker ...... 84 Epoxy-Boron nitride composites for high voltage application ...... 85 Loriane Desmars1,2, Jocelyne Galy1, Damien Bachellerie2, Antonella Cristiano-Tassi2, Servane Haller2, ...... 85 Sébastien Pruvost1,2 ...... 85 Development of thermosetting resins to improve resin performance for industrial applications ...... 89 Xaoqing Zhang, Buu Dao, Tri Nguyen, Mel Dell’Olio ...... 89 Managing flame retardant performance in modern thermoset applications ...... 92 Frank Osterod ...... 92

SESSION 6: INFLUENCING NETWORK STRUCTURE & APPLICATION ...... 96 Influence of the polymer network structure on the thermal stability, the thermal and mechanical properties of epoxy matrix systems ...... 97 Björn T. Riecken, Eike Schröder, Bodo Fiedler ...... 97

8 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

Influence of phenylene ring substitution position on amine cured epoxy resin properties ... 101 Roderick Ramsdale-Capper, Joel P. Foreman ...... 101 Structure study of two cyanate ester resins ...... 105 L. Bailly1,2, B. Hassoune-Rhabbour1, A. Abadie1, B. Boniface2, V. Nassiet1 ...... 105 Nanostructured thermosetting systems with thermo- and electro-responsive ...... 109 Agnieszka Tercjak, Junkal Gutierrez ...... 109 Development of an innovative manufacturing process for the in-LINE COAting of pultruded composites (COALINE project) ...... 111 B. Redondo, N. Lardiés ...... 111 High-pressure RTM in aerospace industry ...... 115 Jan Schiller ...... 115 Characterization of release agents used in resin transfer moulding (RTM) and liquid compression moulding (LCM) processes ...... 117 Jarlath McHugh1, Fabian Grasse2 ...... 117

SESSION 7: PROCESSING...... 118 Uretdione – A versatile building block for outstanding new prepreg systems ...... 119 Eike Langkabel, Zuhal Tuncay, Christina Cron, Guido Streukens ...... 119 New isocyanate based thermoset composite matrix materials with extreme UV, chemical and weathering resistance ...... 123 Dirk Achten, Paul Heinz, Richard Meisenheimer, Florian Golling, Stamo Mentizi ...... 123 Advanced phthalonitrile resins for out-of-outoclave composite manufacturing ...... 127 B.A. Bulgakov, A.V. Babkin, E.S. Afanasieva, A.V. Kepman ...... 127 The processing of a novel polymer matrix for wind turbine blades ...... 131 Bethany K. Russell 1, Carwyn Ward 1, Shinji Takeda 2, Ian Hamerton 1 ...... 131

SESSION 8: TOUGHENING ...... 135 Toughening epoxies using nanoparticles ...... 136 Ambrose C. Taylor ...... 136 The relationship between thermoset resin compressive yielding behaviour and toughenability in addition curing resins ...... 140 Christoph Uhlig1, Olaf Kahle1, Monika Bauer1,2, Oliver Schaefer3, Helmut Oswaldbauer3, ...... 140 Torsten Gottschalk-Gaudig3, Detlev Ostendorf 3, Dirk Ewald4 ...... 140 Latest innovation in core/shell toughening agents for thermosets and composites ...... 144 Aline Couffin1, Philippe Hajji2, Alexandre Vermogen2 ...... 144 Thermoset composites from soluble thermoplastic technology: Control of morphology, in relation with applicative properties ...... 148 Eléonore Mathis, Marie-Laure Michon, Claude Billaud, Didier R. Long ...... 148

SESSION 9: CHEMISTRY ...... 151 Hyperbranched polymers as important components in coatings and resins...... 152 Brigitte Voit ...... 152 Internally acid-catalysed covalent adaptable networks ...... 155 Maarten Delahaye, Johan Winne, Filip Du Prez...... 155 Synthetic approaches to mouldable and recyclable thermosetting lightweight materials ...... 156 Katharina Koschek1, Hannes Schäfer1,2, Tobias Urbaniak1,2, Jonas Werner1 ...... 156

9 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

Temperature dependent size exclusion chromatography for the in situ investigation of thermoreversibly bonding polymers ...... 159 Josef Brandt1, Johannes Lenz1, Kai Pahnke2,3, Friedrich Georg Schmidt4, Christopher Barner-Kowollik2,3,5, Albena Lederer1 ...... 159

SESSION 10: CHARACTERIZATION & APPLICATION ...... 162 Using zinc oxide nanoparticles to improve the thermal stability of a high -performance benzoxazine resin ...... 163 Jérémy Horion1, Carl van Tieghem de ten Berghe1, Leïla Bonnaud2, Christian Bailly1 ...... 163 Development of novel high-temperature polyimide-like inks for PolyJet 3D printing – Curing kinetics and properties of printed material ...... 164 Annika Wagner1, Irina Gouzman2, Nurit Atar2, Eitan Grossmann2, Leo Schranzhofer1, Mariana Pokrass3, Christian Paulik4 ...... 164 High temperature resins and their use in hot flue gas applications ...... 165 Michael Jaeger, Arie van Buren ...... 165 Inline cure monitoring in engineered wood with paper sensors – Inspiration for carbon- prepregs ...... 169 S. Bauer1, B. Liedl2, U. Müller2, R. Schwödiauer1, M. Steiner2, T. Stockinger1, S. Tambe2 ...... 169

POSTER SESSION ...... 173 C/C composites developed from phthalonitrile based composites ...... 174 V.V. Aleshkevich, B.A. Bulgakov, O.S. Morozov, A.V. Babkin...... 174 Core-shell particles with improved dispersibility into epoxy networks ...... 178 Vivien André, Jocelyne Galy, Frédéric Lortie ...... 178 New adhesive films with high glass transition temperature and storage stability at room temperature ...... 179 Monika Bauer, Andreas Bernaschek, Dirk Dietrich ...... 179 Synthesis and characterization of triblock copolymer PLA-PEG-PLA catalyzed by Maghnite- H+ ...... 181 Mohamed Benachour, Amine Harrane, Mohammed Belbachir ...... 181 Requirement and performance of high precise functional coating technologies for the production of prepreg ...... 182 Andrea Glawe, Lutz Böwe ...... 182 Volume dilatometry – Online investigation of shrinkage during thermal or radiation cure .. 186 Yvonne Chowdhury, Dirk Dietrich, Annette Bauer ...... 186 Internally carboxylic acid-catalysed CANs ...... 188 Maarten Delahaye, Johan Winne, Filip Du Prez...... 188 UV-LED curable thermosetting resins and composites thereof - Applications from micrometer to meter scale ...... 189 Christian Dreyer ...... 189 New unsaturated polyesters for thermosets with high heat resistance ...... 190 Marco Grahneis...... 190 Advanced benzoxazine/epoxy hybrid resins and composites ...... 191 Sergiy Grishchuk1, Bernd Wetzel1, József Karger-Kocsis2 ...... 191 Microwave-assisted curing of fiber reinforced plastics - Electromagnetic simulations ...... 194 Lutz Hartmann, Christian Dreyer ...... 194 A thermo-mechanical and rheological approach for the characterization of thermosets in automotive friction materials ...... 197

10 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

Valentina Iodice1, Finizia Auriemma2, Claudio De Rosa2, Mauro Milazzo2, Agusti Sin1 ...... 197 Biobased epoxides as binders for coating electrodes in lithium-ion-batteries ...... 199 Helene Jeske ...... 199 Use of condensate generated during kiln-drying step of wood as a natural formaldehyde scavenger for urea- and melamine-formaldehyde resins ...... 200 Tolga Kaptı1, Nadir Ayrılmış2 ...... 200

Integration of tunable low Tg thermoplastic polymers in thermosetting resins as toughening and damping modifiers ...... 203 Mathias Köhler, Christoph Herfurth, Christoph Uhlig, Antje Lieske ...... 203 Novel transparent organic-inorganic composites based on metal fluoride nanoparticles ...... 207 Thoralf Krahl, Erhard Kemnitz ...... 207 Tailor-made innovative thermoset resins to validate proof of concept in the Industrial world ...... 210 Cédric Loubat, Alain Graillot, Agathe Bouvet-Marchand ...... 210 Biobased building-blocks for repairable, reprocessable and recyclable thermoset epoxy resins ...... 211 Cédric Loubat1, Alain Graillot1, Samuel Malburet1, Aratz Genua2, Alice Mija3 ...... 211 Dual-curing phthalonitrile-propargyl ether resins for CFRP ...... 212 O.S. Morozov, S.Nechausov, B.A. Bulgakov, A.V. Babkin, A.V. Kepman ...... 212 Dual curing hybrid resin ...... 216 Thomas Richter, Reinhard Lorenz ...... 216 How to qualify a resin for SGRE Offshore IntegralBlade® ...... 218 Harald Stecher...... 218 Towards formaldehyde-free and fully biobased resoles for aerospace applications ...... 221 Ségolène Henry1, Romain Tavernier1, Lérys Granado1, Gabriel Foyer2, Ghislain David1, Sylvain Caillol1 ...... 221 Vicinal tricarbonyl compound – The key to reversible crosslinking thermosetting materials ...... 224 Tobias Urbaniak1,2, Katharina Koschek2 ...... 224 Does the ratio between diglycidyl ether of bisphenol A resin and 4,4'-diaminodiphenyl sulfone hardener affect the materials properties of the resulting cross -linked polymer? A molecular dynamics study ...... 225 Pradeep R. Varadwaj1, Paul Fons1, Masataka Ohkubo1,Kiyoka Takagi2 ...... 225 Predicting phase separation in polymer blends that contain branched molecules ...... 228 Emma Wood, Nigel Clarke ...... 228

11 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY

CRYOMILLING: A CRITICAL STEP FOR AC CURATE DETERMINATION OF DEGREE OF CURE AND RESIN CONTENT IN CARBON FIBRE REINFORCED THERMOSET- TING COMPOSITES

Nessa Fereshteh Saniee, Neil Reynolds, Ken Kendall Warwick Manufacturing Group (WMG), University of Warwick, Coventry, UK

Abstract the pan, and therefore the DSC sensor. The above men- tioned variations results in up to ±20% error in the total A new specimen preparation method is proposed for heat measured per normalised weight specimen. Not thermal analysis to characterise the cure kinetic of only do these variations affect the evaluation of the thermosetting fibre-reinforced polymers (FRPs). For degree of cure of the final product, but also makes the instance, differential scanning calorimetry (DSC) thermokinetic analysis of such materials impossible measurements according to commonly used interna- (considering the fact that the neat resin is not provided tional standards leads to coefficient of variation up to by the manufacturers of prepreg in most cases). For the 23% in enthalpy of reaction and a deviation from the composite manufacturer to optimise the cure time, an nominal resin content of up to 17% for inhomogeneous accurate total heat flow of the uncured prepreg is re- materials such as NCF and woven pre-impregnated quired as a reference to avoid premature moulding or (prepreg) composites. To address this issue and de- under-cured product. Traditionally for Thermokinetic crease the coefficient of variation, prepreg fabrics were analysis, DSC specimens are prepared according to cryogenically milled to develop a homogeneous pow- ASTM or ISO standards such as ISO 11357 for 5 heat- der without altering the chemical reaction in the ma- ing rates and modelled with either ASTM standards or trix. The quantitative results showed cryogenic milling free model system. In this study it has been shown that decreased the coefficient of variation in enthalpy of cryomilling is an excellent pre-step that can be used in reaction to as low as 0.2% and deviation from the nom- the analysis of cure kinetics [2]. Cryomilling is a inal resin content of 0.5%. common technique used in multiple industries where the homogenising of materials is crucial but the chemi- Introduction cal characteristics of the materials must stay intact such as nanocomposite and thermoplastics processing [3, 4]. Due to new environmental challenges, novel materials such as carbon fibre reinforced plastic (CFRP) composites are replacing their metallic counterparts in the Experimental procedure transportation industry. Most problems in manufac- Thermal analysis of epoxy based prepreg CFRP was tured CFRP composite parts are related to ineffective performed on samples of ~10 mg in sealed aluminium optimisation of the curing process. To improve the pans with a Mettler Toledo HP-DSC-1 differential quality of the CFRP parts, it is essential to precisely scanning calorimetry (DSC) over a temperature range control and evaluate the cure process[1]. of 30 to 230 °C at a 10 °C/min heating rate under a DSC is one of the most versatile methods that is widely nitrogen flow. Specimens were prepared both with used to monitor the curing of thermosets. The main cryogenic milling and conventional method that is challenge in evaluating the CFRP cure kinetics or de- cutting the samples with a scalpel. Both sets were char- gree of cure is that only the resin contributes to the acterised using DSC, DSC/TGA, FTIR, optical and total heat of reaction, while the carbon fibre generates scanning electron microscopy (SEM) to investigate the no chemical reaction and only manipulates the effec- effect of Cryomilling on the crosslinking and micro- tive weight of the specimen. The degree of cure that is structure of prepreg CFRP composites. directly influenced by the measured heat flow will be inaccurate for the normalised DSC specimen and more Materials likely will be overestimated. This is not the only ad- verse effect of the fibres in the DSC specimens. The The family of the thermosetting CFRPs studied in this best specimens for DSC measurement are in a powder work are commercially available epoxy based prepreg form that allows homogeneous contact at the bottom of materials. Materials were purchased commercially

SESSION 4: CHARACTERIZATION METHODS 71 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY from various suppliers such as Cytec and Mitsubishi in prepreg materials were reported to be below 1% indica- a prepreg form. They were stored at -20 °C in a freezer tive of a highly reproducible process. This can be ex- and were tested within their expiry date. They are plained by knowing that the best samples for thermal named in this work based on their architecture and analysis measurements are in either a liquid or powder nominal carbon fibre content as NCF-50 (EF7312), form to allow maximum contact for heat transfer dur- Woven-40 (368) and unidirectional-30 (368). ing the non-isothermal or isothermal measurements.

Results and discussion Non-isothermal DSC was used to measure the total enthalpy of reaction for the uncured prepreg composites. The total enthalpy of reaction can be calculated by integrating the heat flow as a function of time over the complete exothermic reaction. The resin content can then be calculated from the total heat released in DSC data such that:

퐻푐 퐶푟 = 푥 100 퐻푇 where Cr is the resin content ranging from 0 (no resin) to 100 (only resin). Hc is the total enthalpy of the reac- Figure 2: Resin content measured by DSC and TGA from cryomilling vs hand-cut for woven 40 % prepreg. tion for the prepreg composite and HT corresponds to the total enthalpy of the reaction for the neat resin. To confirm that the variation in the total enthalpy of the curing is not due to the pre-curing during the han- Results and discussion dling of the prepreg materials, simultaneous TGA/DSC was performed (Figure 2) and the respective resin con- The dynamic DSC curves for the epoxy based prepreg tents calculated (Table 1). with a woven structure were examined for 3 hand-cut,

3cryomilled and neat (extracted from the side of the Measured Resin Content (%) prepreg rolls) resins and shown in Figure 1. The hand

cut and cryomilled traces are comparable to each other Materials Cryomilled Hand-cut

with enhanced reproducibility observed with the cry-

omilled samples. Similar results were observed with

SD SD SD SD

DSC DSC TGA the other two types of prepregs. TGA 40.8 0.9 40.1 0.1 39.9 10.9 41.3 8.2

40% Woven Table 1: Resin content by combined TGA/DSC measurements for the cryomilled vs the hand-cut samples.

He et al. has reported that difference in obtained fibre content from TGA analysis is about 1-3 wt % higher than those measured from the processing statistical (PS) method. Furthermore, PS and carbonization in nitrogen (CIN) [5] methods do not show repeatability Figure 1: Schematic illustration of cryomilling process vs hand better than 4.7 wt % [6]. However, these reported val- cut and DSC cure behaviour of woven prepreg. ues are for cured prepreg materials only. It can be ex- pected that an uncured prepreg has more deviation in From the results shown in Table 1, it is clear that cryo- the resin content than the cured part because when the genic milling generates a resin content closer to the resin is at its minimum viscosity it will fill any resin nominal value when compared to the conventional poor areas. Lower standard deviations obtained for the hand-cut DSC samples. This is consistent across each TGA analysis of precured cryomilled samples are of the prepregs. Higher variations can be seen in the achieved when compared to these previously reported prepregs with higher resin content. The highest devia- values highlighting the enhanced accuracy of the cry- tion was measured to be 11.4 % for the biaxial Non- omilled method [2]. For thermosetting resins, there is Crimp Fabric (NCF). The standard deviation for all

SESSION 4: CHARACTERIZATION METHODS 72 PROCEEDINGS OF THE THERMOSETTING RESINS 2018 CONFERENCE, 25 – 27 SEPTEMBER 2018, BERLIN, GERMANY no possibility to use the DSC method for measuring Nominal resin content with the resin content measured carbon content but again using cryomilling to produce by stand-alone DSC is shown in Figure 4 using the a homogeneous powder ensures reliable dispersion of conventional Hand-cut preparation method versus the the fibre for the cured specimen and also improved Cryomilling preparation method for four different contact between the DSC sensor and the aluminium. CFRP uncured prepregs. The faint red line specifies the Table 1 shows that the standard deviation decreased by perfect match. 100 times for the TGA method. The lower reproducibility of DSC could be due to the less sensitive DSC Conclusion sensor used in the hybrid equipment and the use of Alumina crucibles. By using simultaneous DSC-TGA analysis one can get the accurate degree of cure for each part that is essential for manufacturing. In addition, in the extreme case where it might be impossible to gain such information on the neat resin, this method can be used to reverse engineer the total heat if the fibre-volume is known.

References [1] Hardis R. et al.: Composites Part A: Applied Science and Manufacturing. 2013; 49: 100-8. [2] Fereshteh-Saniee N et al.: Composites Part A: Applied Science and Manufacturing. 2018;107: 197-204. [3] Zhu YG etal.: Journal of Polymer Science Part B: Polymer Physics. 2006; 44(21): 3157-64. [4] Delogu F et al.: Progress in Materials Science. 2017; 86: 75-126. [5] Wang Q et al.: Composites Part A: Applied Science and Manufacturing. 2015; 73: 80-4. Figure 3: Optical micrographs of 3 different prepreg systems 5x [6] He H-w et al.: International Journal of Poly- stitched-images of the prepreg systems. mer Analysis and Characterization. 2016; To understand the homogenising effect of Cryomilling 21(3): 251-8. better, optical microscopy was employed and the optical micrographs are shown in Figure 3. The brighter Contact patches are representative of resin rich areas. It is clear that the UD has a more homogenous structure when Nessa Fereshteh Saniee, Ph.D. compared with the other two prepregs in line with the University of Warwick, WMG, International Manufac- lower standard deviation shown in Figure 4. The resin turing Centre poor areas might have been created where the tows are CV4 7AL Coventry crossing due to differences in height. United Kingdom

[email protected]

www.warwick.ac.uk

Figure 4: Four different CFRP uncured prepregs were measured by conventional and cryomilled methods.

SESSION 4: CHARACTERIZATION METHODS 73