Thermosetting polymers can cure at a gradient of cure temperatures due to a variety of factors, including heat transfer in the thermoset during heating and the exotherm due to the chemical reaction occurring during the cure. A new method for assessing the effect of cure conditions on mechanical behavior of toughened thermosets has been developed. Modeling of the phase separation process of a model thermoset system provided detailed understanding of the mechanism of property variation with cure temperature for this material. Subsequent characterization of gradient temperature cured samples has shown important variations, illustrating not only the importance of cure conditions, but the possibility of producing materials with new and useful properties. A special mold was developed to cure samples in a controlled gradient of temperature. Example systems known to show pronounced variations in microstructure cured in this gradient mold showed large variations of microstructure as a function of position within the sample, corresponding to the cure temperature at that point. A model toughened thermoset system was developed to demonstrate gradients of properties following cure in the gradient temperature mold. Cyanate ester materials were modified with hydroxyl-terminated butadiene-acrylonitrile copolymers as well as low Tg amorphous polyesters. The polyesters showed very desirable properties for a toughener, including relatively good thermo-oxidative stability in comparison with the butadiene-acrylonitrile toughener. However, the variation of properties of the cured materials with temperature was small, and to better understand the property variation possible using a gradient cure temperature technique, the butadiene-acrylonitrile toughened cyanate ester system was chosen for further study. This system showed a significant variation of glass transition temperature of the cyanate-rich phase as a function of cure temperature. Modeling of the phase separation process of this material was varied out employing a modeling procedure developed for epoxy materials. Various characteristics of the system were determined in order to apply the model to the chosen toughened thermoset. These included viscosity, surface, and thermodynamic parameters in addition to a careful characterization of the morphological parameters developed during cure at the chosen temperatures. Results show excellent predictive capability of the model for microstructure. Prediction of phase composition as a function of cure temperature is also possible, again with good agreement with experiment results. Higher cure temperatures result in a non-equilibrium phase composition, depressing the glass transition temperature of the continuous cyanate ester rich phase. This provides a mechanism by which properties of the system change as a function of position within a gradient temperature cured sample. Dynamic mechanical analysis was employed to characterize the relaxation properties of gradient and isothermally cured samples. The Havriliak Negami equation was chosen to describe the relaxation behavior of these samples. Comparison of the fitting of isotherms over the small, experimentally accessible range of frequencies showed that the use of time-temperature superpositioning could more reliably discern relatively small differences. The breadth of the relaxation corresponding to the glass transition of the polycyanurate phase was increased with a gradient cure temperature relative to isothermally cured samples. This increased broadness was expressed in an alternative way through the use of an autocorrelation function, which allows direct comparison of the time-dependent transition from a fully unrelaxed condition to a fully relaxed one. / Ph. D.

One of the major classes of polymer matrix resins under consideration for structural composite applications in the infrastructure and construction industries is vinyl ester resin. Vinyl ester resin is comprised of low molecular weight poly(hydroxyether) oligomers with methacrylate endgroups diluted with styrene monomer. The methacrylate endgroups cure with styrene via free radical copolymerization to yield thermoset networks. The copolymerization behavior of these networks was monitored by Fourier Transform Infrared Spectroscopy (FTIR) at various cure conditions. Reactions of the carbon-carbon double bonds of the methacrylate (943 cm-1) and styrene (910 cm-1) were followed independently. Oligomers possessing number average molecular weights of 700 g/mole were studied with systematically increasing levels of styrene. The Mortimer-Tidwell reactivity ratios indicated that at low conversion more styrene was incorporated into the network at lower cure temperatures. The experimental vinyl ester-styrene network compositions deviated significantly from those predicted by the Meyer-Lowry integrated copolymer equation at higher conversion, implying that the reactivity ratios for these networks may change with conversion. The kinetic data were used to provide additional insight into the physical and mechanical properties of these materials. In addition to establishing the copolymerization kinetics of these materials, the development of halogen free fiber reinforced vinyl ester composites exhibiting good flame properties was of interest. Flame retardant vinyl ester resins are used by many industries for applications requiring good thermal resistance. The current flame-retardant technology is dependent on brominated vinyl esters, which generate high levels of smoke and carbon monoxide. A series of halogen free binder systems has been developed and dispersed in the vinyl ester to improve flame retardance. The binder approach enables the vinyl ester resin to maintain its low temperature viscosity so that fabrication of composites via Vacuum Assisted Resin Transfer Molding (VARTM) is possible. The first binder system investigated was a polycaprolactone layered silicate nanocomposite, which was prepared via intercalative polymerization. Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) data indicated a mixed morphology of exfoliated and intercalated structures. The mechanical properties and the normalized peak heat release rates were comparable to the neat vinyl ester resin. Alternative binder systems possessing inherent flame retardance were also investigated. A series of binders comprised of novolac, bisphenol A diphosphate, and montmorillonite clay were developed and dispersed into the vinyl ester matrix. Cone calorimetry showed reductions in the peak heat release rate comparable to the brominated resin. / Ph. D.

In order to reduce over-dependency on fossil fuels and to create an environment that is free of non-degradable plastics, and most importantly to reduce greenhouse gas emission, bio-based products are being developed from renewable resources through intense research to substitute conventional petrochemical-based plastics with renewable alternatives and to replace synthetic fibers with natural fibers. Many authors have done quite a lot of work on synthesizing polymers from renewable origin. Polylactic acid (PLA) has been developed and characterized, and it was found that it has enormous potential and can serve as an alternative to conventional thermoplastics in many applications. Modification of the plant oil triglycerides has been discussed by many authors, and research is still going on in this area. The challenge is how to make these renewable polymers more competitive in the market, and if possible to make them 100% bio-based. There is also a major disadvantage to using a bio-based polymer from plant oils because of the high viscosity, which makes impregnation of fibers difficult. Although natural fibers are hydrophilic in nature, the problem of compatibility with the hydrophobic matrix must be solved; however, the viscosity of the bio-based resin from plant oils will complicate the situation even more. This is why many authors have reported blending of the renewable thermoset resin with styrene. In the process of solving one problem, i.e reducing the viscosity of the renewable thermoset resin by blending with reactive diluents such as styrene, another problem which we intended to solve at the initial stage is invariably being created by using a volatile organic solvent like styrene. The solution to this cycle of problems is to synthesize a thermoset resin from plant oils which will have lower viscosity, and at the same time have higher levels of functionality. This will increase the crosslinking density, and they can be cured at room temperature or relatively low temperature. In view of the above considerations, the work included in this thesis has provided a reasonable solution to the compounded problems highlighted above. Three types of bio-based thermoset resins were synthesized and characterized using NMR, DSC, TGA, and FT-IR, and their processability was studied. The three resins were subsequently reinforced with natural fibers (woven and non-woven), glass fibers, and Lyocell fiber and the resulting natural fiber composites were characterized by mechanical, dynamic mechanical, impact, and SEM analyses. These composites can be used extensively in the automotive industry, particularly for the interior components, and also in the construction and furniture industries. Methacrylated soybean oil (MSO), methacrylic anhydride-modified soybean oil (MMSO), and acetic anhydride-modified soybean oil (AMSO) were found to be suitable for manufacture of composites because of their lower viscosity. The MMSO and MSO resins were found to be promising materials because composites manufactured by using them as a matrix showed very good mechanical properties. The MMSO resin can completely wet a fiber without the addition of styrene. It has the highest number of methacrylates per triglyceride and high crosslink density. / Akademisk avhandling för avläggande av teknologie doktorsexamen vid Chalmers Tekniska högskola försvaras vid offentlig disputation, den 6:e maj, Chalmers, KE-salen, Kemigården 4, Göteborg, kl. 10.00.

Visando o gerenciamento dos artigos têxteis advindos do descarte doméstico e dos refugos gerados nos processos de fabricação, a reciclagem e a reutilização surge como uma resposta emergencial aos problemas ambientais do setor de têxtil e moda. O presente estudo teve como principais objetivos realizar uma revisão bibliográfica sobre técnicas de reuso e reciclagem de têxteis, principalmente das fibras de algodão, bem como temas relacionados à ecologia industrial, ao design de moda e ao eco design. Na sua parte experimental também visou realizar ensaios de microscopia e de determinação de regain da fibra de algodão, bem como ensaios de tração, alongamento e microscopia em compósitos produzidos com três diferentes tipos de resinas termorrígidas (epóxi, poliéster ortoftálico e poliuretano) reforçadas com fibras têxteis de algodão, sugestão possível para a diminuição dos refugos têxteis em aterros sanitários. Para tais compósitos foram apontadas aplicações no setor de moda. Conclui-se que os compósitos produzidos a partir de resíduos têxteis poderiam trazer benefícios ao meio-ambiente, pois além de possuírem atribuições como resistência e coesão, podem ser destinados à área de moda, entre outras áreas, pelos atributos visuais que proporcionam. Assim, são capazes de suprir necessidades específicas de consumo do mercado, ávido por novidades, bem como de suprir a demanda por estudos de novos materiais no setor de têxtil e moda, que carece de bibliografia especifica que reúna uma análise técnica e estética abrangendo todas as fases produtivas de materiais, processos, criação e design. / Aiming management of textiles coming from household waste and scrap generated in the manufacturing processes, recycling and reuse arise as emergency responses to the environmental problems of the textile and fashion industry. The present study main objectives were to perform an interdisciplinary literature review focused on techniques of reuse and recycling of textiles, mainly cotton fibers, as well as topics related to industrial ecology, the fashion design and eco design. On experimental part it also aimed to carry out tests of microscopy and regain determination of cotton fibers as well as microscopy, tensile and elongation tests in composites made with three different types of thermoset resins (epoxy, polyester orthophthalic and polyurethane) reinforced with textile cotton fibers, configuring possible suggestion for the reduction of textile waste in landfills. For applications such composites were pointed in the fashion sector. It is possible to conclude that the composites made from textile waste could bring benefits to the environment, because besides possessing strength and cohesion functions, they could be assigned to fashion design field from the visual attributes they provide. Thus, they are able to supply specific needs of the consumer market, eager for news, and to furnish the demand for studies of new materials in the textile and fashion sectors, which lacks specific bibliography that bring together aesthetic and technical analysis covering all production phases of materials, processes, creation and design.

Biobased thermoset resins were synthesized by functionalizing the tall oil fatty acid with hydrogen peroxide and then methacrylic anhydride. The obtained resins were characterized by FTIR to confirm the conversions. The cross-linking ability of the resins were checked by curing experiments and followed by DSC analysis regarding the extent of cross linking. TGA analysis was conducted to identify the thermal degradation patterns of cured resins. The obtained resins (blended with or without 33wt% styrene) were used as matrix and knitted viscose fibers were used as reinforcements to make bio-based composites. Ten layers of knitted viscose fibers were stacked crosswise (0/90⁰С) and hand lay-up impregnation was performed. The fiber ratio of all composites was around 63-66%. The composites were characterized by flexural testing, dynamic mechanical thermal analysis and charpy testing. This work demonstrates that manufacture of composites with both matrix and reinforcement fiber coming from renewable resources is feasible, and the resulted composites have satisfied mechanical performance. / Program: MSc in Resource Recovery - Sustainable Engineering

<p>Diffusion of liquids into and through polymers is an important factor that negatively may influence the durability or lifetime of a polymer structure used in industrial applications. In this work two types of polymers, a liquid crystalline polymer (LCP, Vectra A950) and various thermoset resins as used in fibre reinforced plastics (FRP) process equipment were studied with regard to barrier properties, chemical resistance and long-term performance. LCP are known for their outstanding chemical resistance and barrier properties. FRP used in process equipment may be a cost-efficient solution in chemically aggressive environments where standard carbon or stainless steel cannot be used due to its limited corrosion resistance. Transport properties of typical industrial environments were determined for the LCP and the influence of annealing and orientation was investigated to study whether the barrier properties can be improved. The possibility to use LCP as cost-effective lining for FRP was explored. Special focus was put on the diffusion of water and its effect on long-term transport properties and stability of thermoset resins as the performance of FRP is strongly related to the diffusion of water. </p><p>The results showed that Vectra A950 was suitable for organic solvent and non-oxidising acid environments. Its transport properties were gravimetrically determined and found to be 10 to 102 times lower than that of a high barrier fluoropolymer of type FEP. The degree of molecular packing increased with annealing time both below and above the melting point. Below the melting point this was – at least – partly due to crystal formation whereas above the melting point other mechanisms were involved. The effects of annealing and orientation on the transport properties in LCP were, however, very small or not significant and probably significantly longer annealing times are required. LCP has potential to be used as lining material for FRP as the use of an LCP-lining substantially reduced the permeability of and the solute sorption in a bisphenol A epoxy-based vinyl ester resin. The bonding strength was improved significantly by a combined abrasive and oxygen plasma treatment.</p><p>The long-term sorption of water in thermoset resins including bisphenol A epoxy-based vinyl ester, novolac-based vinyl ester, urethane modified vinyl ester and bisphenol A polyester resins was found to increase with exposure time whereas the diffusion coefficient was not significantly affected. It was shown that the presence of water induced relaxation processes that were considered to be the primarily reason for the increase in sorption coefficient in comparison to degradation processes, such as hydrolysis, causing osmotic processes. A general relationship for the estimation of the sorption coefficient at 80ºC in dependence of the water activity and the sorption coefficient at unit activity independent of the resin type was established.</p>

La cuisson rapide de préimprégnés est une problématique d'actualité qui sous entend les nécessités de rentabilité dans l'industrie aéronautique. Cette étape est basée sur la maîtrise du degré d'avancement de réaction du système thermodurcissable au cours du cycle qui régit l'ensemble des propriétés finales des pièces composites. La caractérisation et la modélisation cinétique du préimprégné aéronautique M21/T700 sont réalisées en vue d'appliquer des dynamiques de mise en oeuvre rapides applicables sur une installation de thermocompression dotée d'un moule chaué par induction de technologie Cage System de Roctool. La construction de diagrammes Temps Température Transformation et la réalisation d'un couplage thermo-cinétique par éléments finis permettent de proposer des cycles optimisés d'une durée de moins de 2 heures (au lieu de 4h30 en cuisson autoclave), en préservant la présence de particules de thermoplastiques dans la matrice. L'étude des propriétés des plaques fabriquées montre des résultats comparables à ceux obtenus pour des pièces mises en oeuvre lors de cycles standards de fabrication à l'aide du procédé autoclave. / The increase of composite content in aerospace structures requires an improvement of profitability through high curing processes. The curing step is based on the control of the degree of cure of the thermosetting system that governs the final properties of the composite parts. The Cage System technology from the Roctool company enables high curing rates thanks to induction heating system. Thus, the characterization and the kinetic modeling of the M21/T700 aeronautical prepreg have been realized for such sollicitations (i.e. high heating rates). To provide a better temperature control, the thermal and kinetic interactions are also considered by finite element modeling of composite thickness. Time Temperature Tranformation diagrams have been set up to build short curing cycle of less than 2h (instead of 4h30 in autoclave curing), considering the presence of thermoplastic particules. Finally, the part properties are in good agreement with the autoclave cycle recommended by the material supplier.

Visando o gerenciamento dos artigos têxteis advindos do descarte doméstico e dos refugos gerados nos processos de fabricação, a reciclagem e a reutilização surge como uma resposta emergencial aos problemas ambientais do setor de têxtil e moda. O presente estudo teve como principais objetivos realizar uma revisão bibliográfica sobre técnicas de reuso e reciclagem de têxteis, principalmente das fibras de algodão, bem como temas relacionados à ecologia industrial, ao design de moda e ao eco design. Na sua parte experimental também visou realizar ensaios de microscopia e de determinação de regain da fibra de algodão, bem como ensaios de tração, alongamento e microscopia em compósitos produzidos com três diferentes tipos de resinas termorrígidas (epóxi, poliéster ortoftálico e poliuretano) reforçadas com fibras têxteis de algodão, sugestão possível para a diminuição dos refugos têxteis em aterros sanitários. Para tais compósitos foram apontadas aplicações no setor de moda. Conclui-se que os compósitos produzidos a partir de resíduos têxteis poderiam trazer benefícios ao meio-ambiente, pois além de possuírem atribuições como resistência e coesão, podem ser destinados à área de moda, entre outras áreas, pelos atributos visuais que proporcionam. Assim, são capazes de suprir necessidades específicas de consumo do mercado, ávido por novidades, bem como de suprir a demanda por estudos de novos materiais no setor de têxtil e moda, que carece de bibliografia especifica que reúna uma análise técnica e estética abrangendo todas as fases produtivas de materiais, processos, criação e design. / Aiming management of textiles coming from household waste and scrap generated in the manufacturing processes, recycling and reuse arise as emergency responses to the environmental problems of the textile and fashion industry. The present study main objectives were to perform an interdisciplinary literature review focused on techniques of reuse and recycling of textiles, mainly cotton fibers, as well as topics related to industrial ecology, the fashion design and eco design. On experimental part it also aimed to carry out tests of microscopy and regain determination of cotton fibers as well as microscopy, tensile and elongation tests in composites made with three different types of thermoset resins (epoxy, polyester orthophthalic and polyurethane) reinforced with textile cotton fibers, configuring possible suggestion for the reduction of textile waste in landfills. For applications such composites were pointed in the fashion sector. It is possible to conclude that the composites made from textile waste could bring benefits to the environment, because besides possessing strength and cohesion functions, they could be assigned to fashion design field from the visual attributes they provide. Thus, they are able to supply specific needs of the consumer market, eager for news, and to furnish the demand for studies of new materials in the textile and fashion sectors, which lacks specific bibliography that bring together aesthetic and technical analysis covering all production phases of materials, processes, creation and design.

La présente étude vise à comprendre l'influence du comportement visco-élasto-plastique d'une matrice TP (PPS) et TD (Epoxy) sur le comportement en fatigue à haute température de composite tissés à fibres de carbone. Une analyse fractographique a permis de révéler le rôle déterminant des zones riches en matrice au niveau des plis à ±45° dans la chronologie d'endommagement et sur le comportement en fatigue de stratifiés à plis croisés et quasi-isotropes. Afin d'évaluer la contribution de la viscoélasticité et de la viscoplasticité de la matriceTP au comportement thermomécanique des stratifiés C/TP à T>Tg, un modèle viscoélastique de Norton généralisé ont été implémentés dans le code Eléments Finis Cast3m. Une technique de corrélation d’images numériques (CIN) a été mise œuvre pour tester la capacité du modèle à prédire la réponse du stratifié dans le cas de structures à forts gradients de contraintes. / The present work was aimed at investigating the influence of the matrix visco-elastoplasticbehavior on the high-temperature fatigue behaviour of carbon woven-ply TP (PPS)-and TS (Epoxy)-based laminates. A fractography analysis showed that matrix-rich areas at the vicinity ±45° plies proved to be instrumental in modifiyng the damage chronology and the fatigue behaviour of angle-ply and quasi-isotropic laminates.In order to evaluate the contribution of viscoelasticity and viscoplasticity to the thermo-mechanical response of C/TP laminates at T>Tg, a linear spectral viscoelastic model and a generalized Norton-type viscoplastic model have been implemented int the Finite Elements code Cast3m. A digital image correlation technique has been used to validate the model's ability to predict the response of high gradient structures to various loading.

Semiconductor die attach materials for high voltage, high reliability analog devices require high thermal conductivity and retention of dielectric strength. A comparative study of effective thermal conductivity and dielectric strength of selected thermoset/ceramic composites was conducted to determine the effect of ceramic particle size and ceramic particle loading on thermoset polymers. The polymer chosen for this study is bismaleimide, a common aerospace material chosen for its strength and thermal stability. The reinforcing material chosen for this study is a ceramic, hexagonal boron nitride. Thermal conductivity and dielectric breakdown strength are measured in low and high concentrations of hexagonal boron nitride. Adhesive fracture toughness of the composite is evaluated on copper to determine the composite’s adhesive qualities. SEM imaging of composite cross-sections is used to visualize particle orientation within the matrix. Micro-indentation is used to measure mechanical properties of the composites which display increased mechanical performance in loading beyond the percolation threshold of the material. Thermal conductivity of the base polymer increases by a factor of 50 in 80%wt loading of 50µm hBN accompanied by a 10% increase in composite dielectric strength. A relationship between particle size and effective thermal conductivity is established through comparison of experimental data with an empirical model of effective thermal conductivity of composite materials.