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McFadden, Peter Daniel, and Peter Daniel McFadden. "Molecular Engineering of Specialty Thermoset Materials." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626330.
Повний текст джерелаАнотація:
This work seeks to lay the foundation for improved art conservation epoxies by addressing two of the problems which currently limit their use. The first problem with current conservation epoxies is the difficulty of removal post-cure. This can be solved by synthesizing epoxies with thermally re-workable Diels-Alder weak links. The second problem relates to difficulty in identifying epoxy joints in reconstructed artifacts and can be solved by incorporating fluorescent monomers within the epoxy network. The challenge in both of these projects is to ensure that the modified epoxies are still suitable for conservation use.
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Flores, Guillén Marjorie Yusneiry. "Toughness improvement of epoxy thermosets by adding dendritic structures." Doctoral thesis, Universitat Rovira i Virgili, 2013. http://hdl.handle.net/10803/128206.
Повний текст джерелаАнотація:
Las resinas epoxi se encuentran entre los materiales termoestables más importantes utilizados en un gran abanico de aplicaciones tales como adhesivos, matrices para materiales compuestos, recubrimientos de superficies y encapsulamiento de componentes electrónicos. La principal razón de su amplio uso es la buena combinación entre resistencia a la tracción y a la corrosión, rigidez y buenas propiedades eléctricas. Sin embargo, debido a su elevado grado de entrecruzamiento, las resinas epoxi tienen una baja resistencia al impacto, la cual limita su uso en algunas aplicaciones específicas. Para contrarrestar este efecto, a las resinas epoxi se les añaden distintos modificantes entre los que se pueden destacar los polímeros hiperramificados.
En esta tesis doctoral se plantea estudiar el efecto de la incorporación de distintos modificantes poliméricos a resinas epoxi convencionales glicidílicas y cicloalifáticas en el proceso de curado y en las características del material final. Estos agentes modificantes tienen estructuras dendríticas y son polímeros hiperramificados y estrellas. Unos son derivados de los poliésteres comerciales Boltorn® y otros con estructuras hiperramificadas de poliéter o poliéster, previamente sintetizadas y en algunos de los casos modificados en los grupos finales con estructuras alifáticas.
Respecto a los sistemas de curado utilizados han sido diferentes los agentes seleccionados. En primer lugar se estudiaron los diisocianatos catalizados por aminas, sustituyéndose estos catalizadores por triflato de iterbio. El mecanismo de reacción en ambos casos fue estudiado por FTIR y mediante calorimetría pudiéndose determinar las reacciones que tenían lugar y cuantificar la proporción de grupos funcionales presentes en la red. También se estudiaron
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otros agentes como son los anhídridos en presencia de amina terciaria, o los triflatos de lantánido, iniciadores catiónicos. Los sistemas anteriormente citados actúan térmicamente. De forma alternativa se han estudiados sistemas fotoiniciados catiónicos. Finalmente, se ha estudiado un nuevo sistema en dos etapas que se basa en una reacción tipo click (tiol-eno), que tiene lugar fotoquímicamente, y que en presencia de fotoiniciadores catiónicos, genera sales de sulfonio que son iniciadores catiónicos.
Esta Tesis Doctoral está estructurada en diferentes capítulos de la siguiente forma:
Capítulo 1:
Incluye una breve descripción del marco teórico relacionado con los materiales termoestables, así como también un breve resumen de lo reportado actualmente en el campo de los agentes modificantes dendríticos poliméricos, procesos de curado y agentes de curado, teniendo un enfoque particular sobre la mejora de las propiedades de los materiales epoxídicos termoestables. Además, en este capítulo se incluye la descripción del objetivo general y los objetivos específicos de esta Tesis Doctoral.
Capítulo 2:
Corresponde a la parte experimental donde se describen los instrumentos y técnicas utilizadas para la realización de este trabajo.
Capítulos 3 y 4:
Se muestra como en la formación de redes de oxazolidonas¿isocianuratos-éteres, el factor determinante para controlar la cantidad de cada fracción, es la relación entre isocianato y grupos epoxi presentes en las
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formulaciones. Asimismo, la selección del catalizador, base o ácido de Lewis, también modifica la estructura de la red y las propiedades termomecánicas de los materiales termoestables.
Capítulos 5:
Se modifican los grupos hidroxilo finales de hiperramificados tipo Boltorn® con cadenas alifáticas y grupos finales vinílicos o epoxídicos, que se adicionan a formulaciones epoxi/isocianato/amina terciaria. Se estudia el proceso de curado y las características termomecánicas. Se hace especial hincapié en la morfología de los materiales, estudiada por SEM.
Capítulos 6 y 7:
Se modifican los grupos hidroxilo finales de hiperramificados tipo Boltorn® con cadenas de 10-undecenoilo en diferentes proporciones y se adicionan estos modificantes en formulaciones de DGEBA/anhídrido/amina terciaria. Se estudia tanto el proceso de curado como las propiedades del material final. Los valores de resistencia al impacto se relacionan con la morfología observada por microscopia electrónica.
Capítulo 8:
Se introducen como agentes modificantes polímeros hiperramificados con distintos grados de modificación obtenidos por la acilación del poliglicidol y se estudia el efecto que ejercen éstos sobre las distintas propiedades termomécanicas de los materiales termoestables en función del grado de modificación y su compatibilidad con la matriz epoxidica.
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Capítulos 9 y 10:
Muestran la incorporación de polímeros hiperramificados de tipo estrella sintetizadas a partir de núcleos tipo Boltorn de diferente peso molecular y brazos de poli(¿-caprolactona) en formulaciones de epoxi cicloalifática. En el primero de estos capítulos el curado se efectúa en condiciones térmicas utilizando triflato de iterbio como iniciador, mientras que en el segundo se efectúa un fotocurado iniciado por una sal de sulfonio como fotoiniciador.
Capítulo 11:
En este capítulo se propone un nuevo sistema de curado dual en dos etapas que consta de una reacción tiol-eno, que tiene lugar bajo irradiación seguida por un curado térmico de resina epoxi cicloalfática. Esta segunda etapa tiene lugar a temperaturas superiores a los 100ºC y viene iniciada por las sales de sulfonio producidas en la primera etapa a partir de los tioéteres formados y su activación mediante fotoiniciación. La adición de polímeros hiperramificados con terminaciones alílicas, activas en la reacción tiol-eno, permite obtener materiales con altas Tgs, a pesar de la flexibilidad introducida en la red por el tritiol utilizado. El sistema de curado propuesto tiene características latentes con un curado en dos etapas dual fotoquímico-térmico.
La tesis recoge al final las principales conclusiones alcanzadas así como una breve lista con las contribuciones científicas relacionadas con esta tesis doctoral.
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Russo, Claudio. "Dual-curing thiol-acrylate-epoxy thermosets for functional applications." Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/672432.
Повний текст джерелаАнотація:
Avui en dia, cada vegada més aplicacions exigeixen materials amb un disseny complex, missió complicada en
polímers termoestables, i per això el curat dual és una eina extremament útil en el disseny de termoestables. El curat
dual s'obté amb una combinació de dos processos d'entrecreuament de xarxa seqüencials o simultani. Els beneficis
del processat dual es basen en la seva flexibilitat en el processat i en la possibilitat de millorar les propietats del
material curat mitjançant processats en una etapa o en multi etapes. En aquest treball, vam desenvolupar un nou
sistema de doble curat basat en dos reaccions tipus "clic": l'addició de tiol-acrilat de Michael (primera etapa) i la
reacció tiol-epoxi (segona etapa). Aprofitant el sistema desenvolupat, es va demostrar que el processat mitjançant
curat en dues etapes tenia un gran valor potencial en l'aplicació com a unions adhesives, ja que permet un control
dimensional precís de la capa adhesiva i una major resistència adhesiva que el curat en un únic pas. Finalment, el
sistema de doble curat tiol-acrilat-epoxi es va utilitzar per desenvolupar polímers d'activació elèctrica amb memòria de
forma. La capacitat de resposta / activació elèctrica es va obtenir incorporant una làmina elèctricament conductora en
el polímer amb memòria de forma obtingut a partir d'un sistema tiol-acrilat-epoxi i aprofitant el processat dual. En
aquest disseny, el tradicional escalfament directe per calor extern (és a dir, forn) es reemplaça per un escalfament
intern per efecte Joule produït a la capa conductora quan s'aplica un voltatge i que es demostra més eficient.Hoy en día, cada vez más aplicaciones exigen materiales con un diseño complejo, misión complicada en polímeros termoestables, y por ello el curado dual es una herramienta extremamente útil en el diseño de termoestables. El curado dual se obtiene con una combinación de dos procesos de entrecruzamiento de red secuenciales o simultaneo. Los beneficios del procesado dual se basan en su flexibilidad en el procesado y en la posibilidad de mejorar las propiedades del material curado mediante procesados en una etapa o en multi etapas. En este trabajo, desarrollamos un novedoso sistema de doble curado basado en dos reacciones tipo "clic": la adición de tiol-acrilato de Michael (primera etapa) y la reacción tiol-epoxi (segunda etapa). Aprovechando el sistema desarrollado, se demostró que el procesado mediante curado en dos etapas tenía un gran valor potencial en aplicaciones como uniones adhesivas, puesto que permite un control dimensional preciso de la capa adhesiva y una mayor resistencia adhesiva que el curado en un único paso. Finalmente, el sistema de doble curado tiol-acrilato-epoxi se utilizó para desarrollar polímeros de activación eléctrica con memoria de forma. La capacidad de respuesta/activación eléctrica se obtuvo incorporando una lámina eléctricamente conductora en el polímero con memoria de forma obtenido a partir de un sistema tiol-acrilato-epoxi y aprovechando el procesado dual.
Nowadays, more and more applications demand materials with complex shape designs which is a difficult task when working with thermosetting polymers. Dual-curing processing is an extremely valuable tool for thermosets design. It consists in the combination of two sequential of simultaneous crosslinking process. The benefits of dual-curing processing rely on its processing flexibility and the properties enhancement of cured parts by single- or multi-stage scenarios. In this work, we developed a novel dual-curing system based on two “click” reactions: the thiol-acrylate Michael addition (first stage) and thiol-epoxy reaction (second stage). Exploiting the developed system, dual-curing processing was proved to have high potentiality in adhesive bonding application, allowing accurate dimensional control of the adhesive layer and higher adhesive strength than on-step curing. Finally, thiol-acrylate-epoxy dual-curing system was used to develop electroresponsive shape-memory polymers. The electroresponsive ability was obtained incorporating an electrically conductive layer into a thiol-acrylate-epoxy shape-memory polymer taking advantage of the dual-processing. In this design, the direct heating from external sources (i.e., oven) is replaced by a more efficient internal Joule heating produced in the conductive layer when an controlled voltage is applied. The electro activation of the SME resulted in significantly faster recovery and, using a custom-made thermoelectric control, a precise control of the recovery process was achieved
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Kwon, Ojin. "Morphology Development and Fracture Properties of Toughened Epoxy Thermosets." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30660.
Повний текст джерелаАнотація:
The phase separation process of a rubber modified epoxy system during cure was analyzed by a model developed on the basis of a thermodynamic description of binary mixture and constitutive equations for nucleation and growth rates. As epoxy resins are cured, rubber molecules are precipitated from the epoxy matrix to a non-equilibrium composition due to the decrease in the configurational entropy and the increase in the viscosity with conversion. If phase separation takes place in a metastable region, this model can monitor the changes of rubber compositions in both phases as well as the changes in the number and size of rubber particles upon conversion of polymerization. The particle size distribution at the completion of phase separation was also calculated. The effect of cure temperature on the final morphologies of a rubber modified epoxy system was discussed.
The computed particle size distributions for piperidine and diaminodiphenyl sulfone cured systems showed good agreements with experimentally measured values. Depending on the activation energy for viscous flow of the epoxy matrix relative to that for the polymerization, the particle size distribution may show bimodal or unimodal distribution. The size of rubber rich phase increases to a maximum and then decreases with an increase in cure temperature. However, due to limitations of temperature range to probe in an actual experiment, one may observe only either decreasing or increasing particle size as cure temperature increases. The number of rubber particles per unit volume increases for the DGEBA/DDS/ETBN system as cure temperature increases in the temperature range of 30 °C to 220 °C.
Fracture toughness of cured DGEBA/DDS/ETBN system was analyzed in terms of morphologies generated by the temperature variation. Since the volume fraction of rubber particles did not change with cure temperature, the critical stress intensity factor did not vary significantly with cure temperature as expected. However, increases in cure temperature produced smaller but more numerous particles. The critical stress intensity factor normalized by the number density of particles exhibited dependence on the radius of particles to the third power. On the other hand, the critical stress intensity factor normalized by the radius of particles showed a linear dependence with respect to the number density of particles.Ph. D.
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Savonnet, Etienne. "Development of bio-based epoxy thermosets for aerospace launchers." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0022.
Повний текст джерелаАнотація:
La grande majorité des résines époxy utilisées aujourd’hui sont issues ou dérivées du bisphénol-A (BPA). Cependant, le BPA est soumis à de très fortes régulations, notamment vis-à-vis de sa récente classification comme substance chimique extrêmement préoccupante par l’agence européenne des produits chimiques (ECHA). Dans un but d’anticiper les évolutions de régulation, ArianeGroup a décidé de remplacer cette substance chimique de ces formulations. Ces travaux de thèse portent donc sur l’élaboration de nouvelles résines époxy biosourcées ayant des propriétés similaires voire supérieures aux références dérivées du bisphénol-A. Pour cela, une bioplatforme de monomères polyépoxydés issus de la vanilline, du méthyl vanillate, du 2,6-diméthoxyphénol et de l’eugénol a été développée. Ces précurseurs biosourcés ont ensuite été utilisés comme précurseurs de réseaux époxyde par réticulation avec des amines. Les réseaux réticulés biosourcés ainsi obtenus ont démontré des propriétés thermomécaniques remarquables bien supérieures à la référence de type DGEBA, notamment en termes de température de transition vitreuse (>300 °C) et taux de coke (>50%). En parallèle de ces travaux, la synthèse de diamines biosourcées, dérivées de la divanilline, et pouvant être utilisées comme agents de réticulation de résines époxy, a été réalisée. Des réseaux époxyde entièrement biosourcés ont ainsi été synthétisés et présentent des propriétés thermomécaniques prometteusesToday, most of the epoxy resins produced are derived from bisphenol-A (BPA). However, BPA is subject to strong regulations, particularly because of its recent classification as chemical of very high concern by the European Chemicals Agency (ECHA). In order to anticipate new regulations, ArianeGroup has decided to replace this substance in its applications. The aim of this thesis is to develop new bio-based epoxy thermosets with comparable thermomechanical properties as the ones issued from bisphenol-A-based materials. For this purpose, a bio-platform of epoxy monomers from vanillin, methyl vanillate, 2,6-dimethoxyphenol and eugenol was developed. These precursors were cross-linked with amines used as curing agent to obtain bio-based epoxy networks. The latter demonstrated thermomechanical properties well above the DGEBA-type reference, especially in terms of glass transition temperature (> 300 °C) and char content (> 50%). Finally, the synthesis of bio-based diamines derived from divanillin was developed and enabled the synthesis of fully bio-based epoxy networks with promising thermomechanical properties
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Smith, Kiersten M. "Altering an Epoxy-Amine Thermoset's Performance Through Varying Mix Ratios." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2195.
Повний текст джерелаАнотація:
Epoxy resins are used in a number of different industries and therefore have application-specific material requirements, from satellites that require materials that operate in space, to paints and coatings that require high scratch resistance and mechanical durability, to medical devices, designed to be in continuous contact with biological fluids. Commercial epoxy products come with manufacturer’s information explaining the epoxy properties and recommended preparation processing conditions, which may include epoxy resin to curing agent mix ratio (Part A : Part B), cure time, and cure temperature, for example. Due to proprietary reasons, it can be difficult to understand why these values are provided, and more importantly, the consequences when deviating from the prescribed recommendations. When manufacturing bioprocessing products for the medical field, a company is under a limited capacity to change materials of construct. Determining how to modify the processing conditions in order to control the material properties of an epoxy would benefit bioprocessing product manufacturers as it would allow them to use the same epoxy that meets the different application-specific requirements of different products.
Five different epoxy systems that were designed for medical applications were characterized to determine how variations in preparation and processing conditions, such as mix ratio (by weight) and cure conditions, affect the final properties of the cured epoxy, including: glass transition temperature, chemical resistance, and coefficient of thermal expansion. For each system, it was found that one mix ratio would produce a material with a maximum glass transition temperature, while changing the mix ratio with either excess Part A epoxy resin or excess Part B amine curing agent would result in a decrease in the glass transition temperature. A higher glass transition temperature indicates higher crosslink density, as a more tightly crosslinked network requires more thermal energy to reach the “rubbery” phase. This mix ratio did not always coincide with the manufacturer’s specifications, suggesting that these recommendations are potentially application specific. While variations in the curing agent’s chemical composition impacted the final material properties of epoxy, as expected, it was also found that varying the mix ratio and annealing conditions resulted in changes in epoxy material properties. A wide range of experiments provided critical data that supported the idea that a single epoxy formulation can be used to produce epoxy materials with varied performance properties through modifications in the preparation and processing conditions, while still remaining usable to manufacture products.
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Rohly, Alison Marie. "Improving Sustainability in Protective Coating Systems." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/29267.
Повний текст джерелаАнотація:
Sustainability has been a driving factor in the recent development of protective coating systems, from reducing volatile organic compounds (VOC’s), integrating biomass for the replacement of petrochemicals, to reducing the number of synthetic or processing steps within a coating system. Incorporating changes to established technologies requires research initiatives focused on matching or exceeding performance properties while maintaining or lowering costs. As a result, sustainable changes to protective coating systems have been under heavy investigation as market demands shift from petrochemicals to renewable materials.
This research focuses on the development of unique thermoset coating systems and sustainable improvements. The first study explores the hydrolytic stability between a silanol and an isocyanate, a frequently used reaction that has been relatively understudied. Incorporation of potential hydrolytically unstable silyl carbamates into polyurethane systems may decrease the crosslinking efficiency of the overall network, negatively impacting coating performance. As a result, investigation into the stability of silyl-carbamates may prevent further inefficiencies by eliminating use of this chemistry within polyurethane systems. The second study focuses on the development of alkoxysilane sol-gel consolidants for the protection of stone materials. Sustainable approaches to consolidant formulation include the reduction and elimination of solvent while improving consolidating properties through material selection. The last two studies focus on the incorporation of lignin-derived vanillin into epoxy thermosets and melamine formaldehydes, increasing the overall biobased content of each system.Office of Naval Research (FAR0025712)
National Center For Preservation Technology and Training, NCPTT (FAR0028305)
EPSCoR/NSF (FAR0030160)
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Tomuta, Adrian Marius. "New and improved thermosets based on epoxy resins and dendritic polyesters." Doctoral thesis, Universitat Rovira i Virgili, 2013. http://hdl.handle.net/10803/129288.
Повний текст джерелаАнотація:
Epoxy resins constitute a class of thermosets which contains more than one epoxide group per molecule, which are very reactive to many curing agents like aromatic or aliphatic amines, acid anhydrides or isocyanates. They are used as reinforced composites, adhesives, high performance coatings and encapsulating materials. Epoxy thermosets have excellent electrical and mechanical properties, good adhesion to many metals and resistance to moisture and thermal and environment exposure.
Curing agents that show no activity under normal conditions but show activity by external stimulation, like temperature, can be called ’’latent curing agents”. Among the thermal latent curing agents dicyandiamide (DICY) is one of the most employed in epoxy resin technology. The latent nature of this type of curing agents is due to the insolubility in epoxy resins at room temperature. The use of dihydrazides as curing agents has been scarcely reported in scientific literature but there are some dihydrazides commercially available as latent curing agents.
In the present study a series of dihydrazides with different structures were prepared by reaction of dicarboxylic diester with hydrazine hydrate in ethanol. These compounds were studied as curing agents in DGEBA/dihydrazide 2:1 (mol/mol) formulations demonstrating their latent character. In the dihydrazides we have prepared, with aliphatic, cycloaliphatic and aromatic moieties a relationship between the melting point of the dihydrazides and the initial curing temperature was observed with the exception of the cycloaliphatic dihydrazide, which was amorphous but initiate the cure at the highest temperature.En esta tesis, hemos sintetizado y caracterizado una familia de dihidrazidasque han sido utilizadas en el curado térmico de resinas epoxi (DGEBA). Asimismo, se han sintetizado nuevos poliestereshiperramificados con grupos finales no reactivos como modificantes de resinas epoxi, curadas con dihidrazidas y con anhídridos y se han caracterizado los termoestables obtenidos. También hemos sintetizando estructuras dendríticas tipo estrella con núcleos de poliéster aromáticos y brazos de policaprolactona. Estas estructuras se han utilizado como agentes modificantes de sistemas epoxi/anhídrido y epoxi/triflato de iterbio. Se ha podido demostrar la mejora de la tenacidad en los materiales termoestables y de su degradabilidad química, manteniendo sus buenas características termomecánicas.
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Park, In. "Mesostructured silica for the reinforcement of thermoset epoxy polymers." Diss., Connect to online resource - MSU authorized users, 2006.
Знайти повний текст джерела
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de, Souza Lucio R. "SYNTHESIS AND APPLICATION OFHIGH PERFORMANCE BENZOXAZINE-EPOXY COPOLYMERS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1618528984888642.
Повний текст джерела
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Foix, Tajuelo David. "Hyperbranched polymers and other highly branched topologies in the modification of thermally and uv cured expoxy resins." Doctoral thesis, Universitat Rovira i Virgili, 2011. http://hdl.handle.net/10803/52795.
Повний текст джерелаАнотація:
RESUM
Les reïnes epoxi constitueixen un dels polímers més emprats en el món de la industria, si bé presenten una sèrie d’inconvenients, els més importants dels quals són: la seva inherent fragilitat, la seva excessiva resistència tèrmica que en dificulta l’eliminació d’un substrat un cop finalitzada la seva vida útil i l’encongiment que experimenten durant el procés de curat. Per tal de reduir o eliminar aquests problemes aquesta tesi proposa l’ús de polímers hiperramificats així com polímers estrella i copolímers lineal-hiperramificat de bloc com a modificants químics de reïnes comercials. Amb aquesta estratègia s’han aconseguit millorar la tenacitat degut a efectes flexibilitzants o a separacions de fase del modificant en la matriu epoxídica, així com reduir l’encongiment en el curat o la degradabilitat de les reïnes, sense afectar altres propietats de la reïna com la seva Tg o la seva duresa.ABSTRACT Epoxy resins are one of the most used polymers in the field of technological applications. However, they present some drawbacks being the most important the following: they are inherently brittle materials; they present excessive thermal resistance that limits their reworkability; and the shrinkage they experiment during curing. To overcome these problems this thesis proposes the use of hyperbranched polymers, as well as star polymers and lineal-hyperbranched block copolymers as chemical modifiers of commercially available epoxy resins. With this strategy tougher materials have been obtained due to either a flexibilizing effect or a phase separation of the modifier within the epoxy matrix. Moreover, the shrinkage on curing and the degradability of the thermosets have been improved without compromising other properties of the resin such as its Tg or its hardness.
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Zeytin, Cigdem. "Synthesis And Characterization Of Epoxy-acrylate Vinylester Resin And Network Structure." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12610115/index.pdf.
Повний текст джерелаАнотація:
Vinylesters are termosets resins that have reactive double bond at the chain ends. They are produced by the reaction of various epoxies and acrylic acids by step growth polymerization. Vinylester chains are oligomers with molecular weight from 600 to 1200 g/mol. The resin viscosity is very hightherefore, diluent is used for easy application. The generally used diluent is styrene with, reactive double bonds to form a crosslink between the chains. The diluted resin viscosities are between 200 &
#8211
2000 cps. Peroxide initiators are used for network formation. The mechanical properties of vinylester resin are enhanced with reinforcements such as glass fiber, carbon fiber, Kevlar or nanoparticules to make composites. Various molecular weights of vinylester resins were synthesized and the samples were prepared with different styrene contents. The effects of the styrene content, temperature and molecular weight on the viscosity were measured and examined. The main effects were determined as styrene content and temperature, while the effect of molecular weight is negligible. The resins were characterized with IR and NMR spectroscopy. The molecular weights were determined by theoretical calculations, titration and H-NMR spectroscopy. Peroxide initiators were used to cure the resins with the cobalt complex accelerator. The resins were post-cured at different temperatures. The completion of the curing was monitored by the disappearance of the carbon-carbon double bonds of methacrylate (943 cm-1) and styrene (910 cm-1), by FT-IR spectrum. The effects of styrene content, post-cure conditions, and molecular weight on the mechanical properties were discussed. The glass transition temperatures were determined by DSC and DMA. The crosslink densities and rheological properties were determined by creep test. The important properties of vinylester resins, which are modulus, tensile and flexural strength, shrinkage, water absorption, glass transition temperature, HDT values and impact strength were investigated.
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Kazilas, Michalis C. "Acquisition and interpretation of dielectric data for thermoset cure monitoring." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/97.
Повний текст джерелаАнотація:
The interpretation and modelling of the dielectric response of thermosetting materials during cure was the main focus of this study. The equivalence of complex permittivity and complex impedance in terms of information content was outlined in a series of case studies covering the separate effects of dipolar movements and charge migration as well as the combined effect of the two polarisation mechanisms. Equivalent electrical circuits were used in order to model the evolution of the complex impedance during cure. A numerical method that can model consecutive spectra throughout the cure was developed. The method is based on Genetic Algorithms and requires only input from the modelling of the initial spectra. Complex impedance spectra were collected during the cure of a commercial epoxy resin formulation under isothermal and dynamic heating conditions. The spectra were analysed and modelled. The modelling was successful over the whole frequency range of the measurements (1 Hz – 1 MHz). The analysis of the estimated model parameters showed that charge migration dominates the dielectric response in a wide frequency range. In addition, the modelling algorithm also distinguished between the effects of electrode polarisation and dipolar movements in the signal. A new equivalent circuit was used in order to map the frequency regions where the each one of the three phenomena that together comprise the dielectric signal can be monitored most effectively. A chemical cure kinetics model was developed for the studied system. A correlation between the maximum point of the imaginary impedance spectrum and the reaction conversion was established. A mathematical model, based on a simple linear dependence of the dielectric signal on conversion and temperature, was built. The model predictions agreed well with the experimental data. The aim of simplifying the interpretation of the dielectric signals led to the development of a new experimental technique. Temperature Modulated Dielectric Analysis employs temperature modulations superimposed on an underlying thermal profile in order to separate the influence on the signal of the temperature alone from that of the cure reaction. The early study carried out here shows that such measurements are feasible and reveals important issues for its further development.
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Girouard, Natalie. "Cellulose nanocrystal thermoset composites: A physical and chemical route to improving dispersion and mechanical properties." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54928.
Повний текст джерелаАнотація:
Cellulose nanocrystals (CNCs) are crystalline nanoparticles that are extracted from renewable sources such as trees or bacteria through mechanical or chemical treatments of their source. CNCs are of interest to several research communities concerned with sustainable technologies. Specifically, CNCs have attracted great interest in the polymer composite community given their high theoretical specific strength and modulus. Two key obstacles surround the use of CNCs in polymer composites, namely their comparatively lower thermal stability and hydrophilicity render their dispersion, and therefore mechanical reinforcement, in polymer matrices challenging. This research considered a waterborne epoxy and a polyurethane elastomer for CNC/polymer composites since these composites are seldom reported in literature or often suffer from degraded mechanical properties. In the epoxy/CNC composites, samples were prepared by two methods, first an epoxy emulsion was mixed with an amine crosslinker and an aqueous based CNC suspension (1-step mixing), and second, the epoxy emulsion was premixed with the aqueous based CNCs and the amine crosslinker was added some time later (2-step mixing). Both composites were mixed by magnetic stirring, however the samples prepared by the 2-step mixing method exhibited enhanced dispersion and mechanical properties, specifically the storage modulus (E’), tensile strength, and work of fracture. Zeta potential measurements and chemical analysis by FTIR indicated that the dispersion mechanism was physical in nature, rather than chemical. In the second composite system, CNCs were chemically modified with an isophorone diisocyanate (IPDI) monomer having unequally reactive isocyanate groups. The goal of the modification step was to react only one isocyanate group with the CNC surface and have a free isocyanate group available for further modification. The chemical structure of one linked isocyanate (urethane bond) and one free isocyanate was confirmed by FTIR and 13C NMR. The particles modified by IPDI (m-CNC) and the neat particles (um-CNC) were incorporated into a polyurethane matrix based on IPDI and a triol crosslinker. Upon visual inspection of the cured composites, it was clear that the modification step produced homogeneously dispersed nanoparticles in the polyurethane while the um-CNCs were aggregated. When the mechanical properties were tested by uniaxial tensile testing, it was determined that the m-CNC composites resulted in improvements in the tensile strength and work of fracture without degradation of the elongation of break property when compared to the neat matrix. Overall the findings in this research highlight important considerations for designing CNC/thermoset composites with enhanced dispersion and mechanical performance.
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Mora, Anne-Sophie. "Élaboration de revêtements époxy pour contact alimentaire à empreinte environnementale réduite A perspective approach on the amine reactivity and the hydrogen bonds effect on epoxy-amine systems vanillin-derived amines for bio-based thermosets synthesis of biobased reactive hydroxyl amines by amination reaction of cardanol-based epoxy monomers synthesis of pluri-functional amine hardeners from bio-based aromatic aldehydes for epoxy amine thermosets cardanol-based epoxy monomers for high thermal properties thermosets." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2019. http://www.theses.fr/2019ENCM0012.
Повний текст джерелаАнотація:
Les travaux de thèse présentés sont issus d’une collaboration industrielle avec la société Nouvelle Sogatra, spécialisée dans la conception, la fabrication et la commercialisation de revêtements de protection bi-composants répondant aux normes d’alimentarité. L’objectif principal de ce projet est de proposer de nouveaux revêtements époxydiques performants en utilisant des produits biosourcés et, dans l’idéal, moins dangereux pour l’Homme et pour l’environnement. Ces travaux de thèse s’axent autour de l’identification de nouvelles méthodologies de synthèse de durcisseurs aminés biosourcés qui soient facilement applicables industriellement.L’amination directe des groupements époxy par ouverture de cycle en présence d’ammoniaque ainsi que l’amination réductrice via la synthèse d’imine ont été sélectionnées comme voies de synthèse pour leur facilité d’application et leur caractère respectueux de l’environnement. Pour cela, des précurseurs commerciaux biosourcés et/ou à toxicité réduite ont été sélectionnés. De nouveaux durcisseurs aminés ont été synthétisés à partir de bio ressources telles que la vanilline, le cardanol et le benzaldéhyde. Ces durcisseurs ont ensuite été utilisés pour la synthèse de système époxy-amine thermodurcissables dont les propriétés physico-chimiques et thermodynamiques ont été caractériséesThe presented PhD works were initiated by an industrial collaboration with the company Nouvelle Sogatra, specialized in the design, manufacturing and marketing of two component protective coatings for food contact. The aim of this project is to offer new high-performance epoxy thermosets from bio based reactants and, ideally with a low impact on the health and the environment. This PhD works focus on the identification of new synthesis methodologies of bio-based amine hardeners, which could be easily industrialized.The direct epoxy amination by ring opening using ammonia and the reductive amination via imine synthesis were selected as synthesis routes for their simple utilization and their eco friendly character. Hence, bio based and/or reduced toxicity commercial precursors were selected. New amine hardeners were synthesized from bio resources, such as vanillin, cardanol and benzaldehyde. These hardeners were then used to synthesize epoxy-amine thermosets, whose thermomechanical and physicochemical properties were characterized
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Cho, Hosouk. "Chemical incorporation of polyhedral oligomeric silsesquioxane into thermoset matrices." Diss., Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
Повний текст джерела
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Fache, Maxence. "Fonctionnalisation et polymérisation de dérivés phénoliques naturels : Vers des matériaux aromatiques biosourcés Vanillin, a key-intermediate of biobased polymers Vanillin, a promising biobased building-block for monomer synthesis Biobased epoxy thermosets from vanillin-derived oligomers Amine hardeners and epoxy cross-linker from aromatic renewable resources Epoxy thermosets from model mixtures of the lignin-tovanillin process." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0014.
Повний текст джерелаАнотація:
Ce travail s'inscrit dans le domaine très actif de la synthèse de polymères biosourcés. Les polymères époxy ont été choisis comme cible car ils présentent une double problématique de substitution du bisphénol A et d'utilisation de ressources renouvelables. L'objectif de ce travail est donc de préparer des polymères époxy biosourcés et d'évaluer leur potentiel en tant que substituts des solutions actuelles. Afin d'atteindre des propriétés thermo-mécaniques suffisantes, des composés naturels aromatiques doivent être utilisés. En effet, le cycle aromatique apporte rigidité et stabilité thermique au réseau. La vanilline est une des seules molécules aromatiques extraites de la biomasse qui soit disponible en quantités industrielles. Elle est obtenue par dépolymérisation en milieu basique et oxydant de lignine. Récemment, la préparation de polymères renouvelables à partir de vanilline a été intensivement explorée ; une revue sur ce sujet a été rédigée. La vanilline a servi de brique de base pour la préparation d'une plateforme de dérivés possédant des fonctionnalités variées. Des monomères diamine, diepoxy, ou dicyclocarbonate dérivés de vanilline ont – entre autres – été synthétisés. Les monomères diepoxy ont été réticulés avec un durcisseur amine commun et les polymères obtenus ont été caractérisés. Leurs propriétés thermo-mécaniques ont été reliées à la structure des monomères. Ces polymères époxy potentiellement biosourcés ont des propriétés comparables à la référence à base de bisphenol A. Afin de pouvoir moduler ces propriétés, des oligomères époxy de longueurs différentes ont été synthétisés à partir de vanilline selon la même méthode que celle utilisée industriellement. Ces oligomères et les polymères époxy qui en sont issus présentent effectivement des caractéristiques modulables. D'autres méthodes de contrôle des propriétés ont été testées, comme la préparation et la polymérisation de nouveaux durcisseurs aminés biosourcés, ou celle d'un monomère époxy trifonctionnel à partir de vanilline. Le polymère potentiellement biosourcé préparé à partir de ce dernier composé présente de meilleures propriétés que la référence à base de bisphénol A. Finalement, un travail portant plus sur la ressource a été réalisé. Des mélanges de composés phénoliques modélisant les produits obtenus lors du procédé de synthèse de vanilline à partir de lignine ont été préparés. L'utilisation de tels mélanges au lieu de la vanilline pure serait bénéfique autant économiquement qu'écologiquement. Ces mélanges ont été glycidylés, puis polymérisés, et les matériaux obtenus caractérisés. Les excellentes propriétés obtenues permettent d'envisager d'intégrer ce débouché à une bioraffinerieThe background of this work is the synthesis of bio-based polymers, a very active area of research. Epoxy thermosets were chosen as target because of the double problematic of bisphenol A substitution and of renewable resources use. Thus, the aim of this work is to prepare bio-based epoxy thermosets and to evaluate their potential as substitutes of current formulations. In order to display good thermo-mechanical properties, these polymers have to be prepared from renewable aromatics. Indeed, aromatic cycles bring rigidity and thermal stability to the network. Vanillin is one of the only aromatic molecules available from biomass at an industrial scale. It is obtained from the alkaline oxidative depolymerization of lignin. Recently, the preparation of renewable polymers from vanillin has been intensively explored; a review on this subject was compiled. Vanillin served as a building-block to prepare a platform of derivatives bearing various functions. Di-amine, di-epoxy, or di-(cyclic carbonate) monomers – among others – were synthesized. The di-epoxy monomers prepared were cross-linked with a common amine hardener and the polymers obtained were characterized. Their thermo-mechanical properties were linked to the monomers structure. These potentially bio-based epoxy thermosets have properties comparable to the bisphenol A-based reference. In order to tune these properties, vanillin-based epoxy oligomers were synthesized by the same method as the one used industrially. The properties of these oligomers and of the thermosets prepared from them could indeed be modulated. Other means of controlling the properties were tested, like the preparation and polymerization of new bio-based amine hardeners, or of a vanillin-based, tri-functional epoxy monomer. The thermoset prepared from this last compound displayed better properties than the bisphenol A-based reference. Finally, a work more centered on the resource was performed. Mixtures of phenolic compounds modelling the products of the lignin-to-vanillin process were prepared. The use of such mixtures instead of pure vanillin could be advantageous both from an economic and an ecologic point of view. These mixtures were glycidylated, polymerized, and the materials obtained were characterized. The excellent properties displayed by these materials allow a potential integration of this strategy in a bio-refinery
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Paris, Christophe. "Étude et modélisation de la polymérisation dynamique de composites à matrice thermodurcissable." Phd thesis, Toulouse, INPT, 2011. http://oatao.univ-toulouse.fr/6966/1/paris_partie_1_sur_2.pdf.
Повний текст джерелаАнотація:
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.
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Stemmelen, Mylène. "De la fonctionnalisation d'une huile végétale aux matériaux polymères bio-sources : étude de lipopolymères en solution et de résines epoxy lipidiques." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20077.
Повний текст джерелаАнотація:
Ce travail de thèse examine trois voies de valorisation de l'huile de pépins de raisin au travers de l'élaboration de matériaux polymères auto-associatifs, réticulés ou hybrides. L'huile végétale ou un modèle lipidique (l'oléate de méthyle) sont d'abord fonctionnalisés grâce à leurs insaturations menant à des huiles hydroxylées, aminées, ou phosphorées.Dans une première étude, l'huile et l'oléate de méthyle ont été hydroxylés par réaction thiol-ène. Les alcools gras sont ensuite transformés en macroamorceurs capables d'amorcer la polymérisation cationique par ouverture de cycle de la 2-méthyl-2-oxazoline. Les lipopolymères (LipoPOx) amphiphiles ainsi synthétisés sont capables de s'auto-associer et de former des nanoparticules monodisperses observées par DLS. Dans une deuxième étude, l'huile et certains de ses dérivés amide ont été modifiés sous UV par addition radicalaire du chlorure de cystéamine, conduisant à une diamine linéaire et à une polyamine ramifiée. Ces dernières ont été utilisées comme durcisseurs d'huile époxydée permettant la réticulation de résines époxy à fort taux de carbone biogénique. L'étude thermomécanique par analyse rhéologique montre que ces matériaux thermodurcissables ont des Tg comprises entre -38 et -9°C.Dans une troisième étude, les lipides ont été fonctionnalisés par addition radicalaire de diméthylphosphite par voie photochimique ou thermique. La transformation ultérieure des esters phosphonés en fonctions silylées a rendu ces composés réactifs vis-à-vis du titane et de ses oxydes. L'ancrage de lipides sur des particules de TiO2 ou des feuilles de Titane influe sur leurs propriétés de surfaceThis Ph-D work deals with the valorization of grapeseed oil for the preparation of novel and various bio-based polymers. Three pathways are developed starting from lipids and leading to polymeric materials such as self-assembled polymers, thermosets and hybride polymers. First, the vegetable oil and methyloleate were modified using radical addition on their double bonds. Following, hydroxylated, aminated and phosphonated lipids were synthesized.In a first study, the oil was hydroxylated via thiol-ene coupling reaction. The fatty alcohol was then converted into initiator for the cationic ring-opening polymerization of 2-methyl-2-oxazoline. These Lipopolymers so-called LipoPOx exhibit hydrophilic POx block and fatty block. Their amphiphilic nature confer them a self-organization ability in water. A monomodal and narrow distribution of nanoparticles was observed by DLS and AFM.In a second study, the oil and some fatty amides were also functionalized by UV-induced radical addition using cysteamine hydrochloride. A linear diamine and a branched polyamine were synthesized and used as hardeners of epoxidized vegetable oil leading to thermosets with high level of bio-carbone. The investigation on thermo-mechanical properties showed a Tg between -38 and -9°C.In a last study, the lipids were modified by radical addition of dimethylphosphite using thermal or photochemical process. Then, the phosphonate esters were converted into silylated moieties making them reactive toward titanium. The anchoring of lipids onto titanium based materials induced a modification of their surface properties
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Menard, Raphaël. "Synthèse de retardateurs de flamme phosphorés biosourcés pour résines époxy Synthesis of biobased phosphate flame retardants Synthesis of biobased phosphorus-containing flame retardants for epoxy thermosets Comparison of additive and reactive approaches From bio-based phosphorus-containing epoxy monomer to fully bio-based flame-retarded thermosets Synthesis of new flame-retardants by radical chain transfer copolymerization of glycidyl methacrylate and dimethoxy-phosphorylmethyl methacrylate." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0013.
Повний текст джерелаАнотація:
La toxicité avérée et le caractère bio-accumulatif des retardateurs de flamme halogénés usuels (PBDE) ont entrainé la mise en place de restrictions d'usage au sein de l'union européenne (REACH). Les retardateurs de flamme phosphorés (RFP) se sont imposés comme alternatives aux solutions halogénées pour leur moindre toxicité et leurs propriétés ignifugeantes adaptées à la composition chimique des résines époxy. Avec l'essor des résines époxy biosourcées, la dépendance aux ressources fossiles pour la synthèse des additifs en tout genre qui entre dans leur composition est devenue problématique. Ainsi, ces travaux s'inscrivent dans une dynamique de développement durable à travers la valorisation d'un composé biosourcé représentatif des structures phénoliques disponibles: le phloroglucinol. La fonctionnalisation directe du phloroglucinol par des groupements phosphates a permis de réaliser une première série d'additifs RFP biosourcés présentant une action ignifugeante prononcée en phase condensée qui réduit le pouvoir calorifique des matériaux ignifugés. A l'échelle macroscopique, une forte intumescence entraîne une décomposition partielle du matériau ignifugé par effet barrière du résidu formé. Cependant, ces additifs réduisent fortement les températures de transitions vitreuse et mécanique par plastification du réseau thermodurcissable. La fonctionnalisation en deux étapes du phloroglucinol a conduit à deux RFP biosourcés additif (P3SP) et réactif (P2EP1SP) de structures comparables. Nous avons ainsi pu mettre en évidence l'intérêt de l'approche réactive qui, en plus de garantir la durabilité des propriétés des matériaux ignifugés, permet une meilleure action en phase condensée qui entraîne une plus forte intumescence. L'approche réactive semblant plus performante, nous avons poursuivi avec la synthèse d'un dernier RFP biosourcé réactif (P2EP1P) dont la structure a été adaptée pour réduire l'effet plastifiant du groupement phosphoré. Enfin, l'étude de différents matériaux 100 % biosourcés contenant le RFP P2EP1P a montré que les inconvénients de l'approche réactive dus à la faible fonctionnalité du RFP réactif peuvent en partie être compensés par l'incorporation d'un co-précurseur époxy de haute fonctionnalité ou d'un agent de réticulation biosourcé aromatiqueThe toxicity and the bioaccumumulative character of the usual halogenated flame retardants(RFX) lead to uses restrictions of the main FRX (PBDE) in the EU as REACH. The phosphorus-containing flame retardants (FRP) are suitable for the epoxy thermoset because of their action on the hydroxyl groups. Moreover, the FRP are less toxic than the FRX. With the rise of the biobased epoxy thermosets, the dependence on fossil fuels for the additives synthesis has become problematic. Thus, these works are designed in a sustainable development approach through the valorization of a biobased compound which is representative of the biobased phenolic structures. The directe functionalization of the phloroglucinol with phosphate functions has achieved a first generation of biobased additives FRP which exhibit a significant action in the condensed phase and reduce the heat released during the thermal degradation of the fire retarded thermosets. This effect results in a strong intumescence at macroscopic scale and the expanded residue acts as a barrier and leads to a partial degradation of the thermoset. However, these additives plasticize the thermoset network and reduce the glass and the mechanical transition temperatures. A two-steps functionalization of the phloroglucinol leads to two new biobased FRP, an additive (P3SP) and a reactive (P2EP1SP), with similar chemical structures. We were able to highlight the benefit of the reactive approach which favors the condensed phase action and the intumescence. Moreover, the reactive approach ensures the durability of the flame retarded thermoset properties. Since the reactive approach seems more efficient than the additive one, an other reactive FRP was synthesized, whose the structure was optimized to reduce the plasticizing effect of the phosphorus-containing group. Finally, the study of different 100% biobased phosphorus-containing thermosets highlighted that the disadvantages of the reactive approach may be balanced by the incorporation of a high functionality epoxy precursor or an aromatic curing agent
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Aucher, Jérémie. "Etude comparative du comportement composites à matrice thermoplastique ou thermodurcissable." Phd thesis, INSA de Rouen, 2009. http://tel.archives-ouvertes.fr/tel-00557897.
Повний текст джерелаАнотація:
Cette thèse consiste en une étude comparative des propriétés thermomécaniques de composites tissés à matrice thermoplastique (PEEK ou PPS) et thermodurcissable (époxy). Une analyse bibliographique a permis la comparaison les comportements des ces stratifies en fonction de la nature de la matrice, de la sollicitation et des conditions environnementales. Une étude expérimentale a conduit à une base de données des trois matériaux sous diverses sollicitations mécaniques (essais monotones élémentaires et structures) et différentes conditions environnementales (température et V.H.). Des essais sur assemblages boulonnes (simple et double recouvrement) ont également été réalisés. Une technique de mesure de champ par corrélation d'images numériques a permis d'étudier le comportement de stratifies troues. Enfin, un modèle de comportement élastoplastique orthotrope de stratifies tisses a matrice thermoplastique a été implémenté dans le code E.F. cast3m et valide pour différentes températures.
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Matoušová, Klára. "Dielektrické vlastnosti epoxidových pryskyřic." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-402126.
Повний текст джерелаАнотація:
This diploma thesis deals with the fundamental properties of epoxide mixtures, as determining of these fundamental properties of epoxide mixtures could in the case of favorable results lead to diminishing the amount of defects in epoxide-embedded instrument transformers. As the influence of effects in the manufacturing process of transformers causing poor quality is very extensit, the biggest emphasis is laid capitally on the influence of the epoxide casting mixture composition. The thesis describes the manufacture technology including used methodics and materials. The compositions of epoxide resins and the mechanisms of their curing. Also, the definitions of fundamental properties of dielectric materials and the description of diagnostic methods used to relative permitivity, dissipation factor and inner resistivity are included. suitable casts of acquired samples were set and dried out within the experimental part, followed by measurement of fundamental electrical properties in temperature and frequency relations. Hereafter a comparison of individual samples and the evaluation of their electrical properties will be carried out.
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Horák, Luděk. "Analýza elektrických vlastností epoxidových pryskyřic s různými plnivy v teplotní a kmitočtové závislosti." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-376991.
Повний текст джерелаАнотація:
Presented master's thesis is focused on studying electroinsulating epoxy resin-based sealings. It describes the chemical composition, production, properties and measuring methods of basic electric quantities of these materials. The aim of the thesis is to compare several sets of samples of composite epoxy resins with different kinds of micro-ground siliceous sand as a filling. The temperature and frequency dependence of relative permittivity, dissipation factor and inner resistivity are measured for given samples.
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Pavlík, Ondřej. "Návrh kompozitní objímky rotoru vysokootáčkového rotačního stroje." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382567.
Повний текст джерелаАнотація:
The diploma thesis focuses on manufacturing carbon fiber and epoxy composite material using filament winding method. Material properties of manufactured composite are ap-proximated using analytical and numerical homogenization models. Calculated material properties are applied to design and evaluate reserve factor of retaining sleeve for high speed brushless permanent magnet synchronous motor. Margin of safety of designed rotor is evaluated using composite failure criteria. Test stand for both static and dynamic testing is designed, static test stand is manufactured and assembled. Static strength test is carried out.
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Seghini, Maria Carolina. "Mechanical Analysis and Fibre/Matrix Interface Optimization for Next Generation of Basalt-Plant Fibre Hybrid Composites." Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0003.
Повний текст джерелаАнотація:
La prise de conscience mondiale des enjeux environnementaux a conduit à l’émergence de composites«verts», dans lesquels les fibres naturelles sont amenées à remplacer les fibres synthétiques. Ces nouveaux matériaux offrent des alternatives écologiques aux composites synthétiques traditionnels mais sont difficilement utilisables pour des applications semi-structurales ou structurales. Une solution possible à ce problème est le développement des composites hybrides, en combinant ensemble fibres naturelles et synthétiques. Dans ce cadre, l'objectif de cette étude était de développer des composites hybrides à base de fibres de basalte et de lin. Les composites hybrides ont été élaborés par moulage par infusion sous vide avec une matrice époxy. À des fins de comparaison,des composites 100% à fibres de lin et100%à fibres de basalte ont également été produits. Une caractérisation mécanique quasi-statique et dynamique amontré que l'hybridation permet d’obtenir un composite avec des propriétés mécaniques intermédiaires comparées à celles des composites à fibres de lin ou de basalte. Cependant, l’analyse approfondie des dommages a montré la nécessité d'optimiser la qualité d'adhésion de l'interface fibre/matrice afin d'accroître les performances mécaniques des composites hybrides obtenus. Pour cette raison, différents traitements de modification de surface ont été développés et étudiés pour les fibres de lin et de basalte. Un traitement physique par plasma (Plasma Enhanced Chemical Vapor Deposition) a été appliqué aux fibres de lin et de basalte. Les fibres de lin ont également été soumises à deux traitements chimiques utilisant des espèces enzymatiques et du CO2supercritique. Les effets des traitements sur la stabilité thermique, la morphologie et les propriétés mécaniques des fibres de lin et de basalte ont été étudiés. L’adhérence fibre/matrice a été analysée en réalisant des tests de fragmentation sur des composites monofilamentaires. La qualité de l'adhésion entre les fibres et les matrices époxy et vinylester a été évaluée en termes de longueur critique de fragment, de longueur de décohésion interfaciale et de résistance au cisaillement interfacial. La micto-tomographie haute résolution a été utilisée pour analyser les mécanismes d'endommagement lors des tests de fragmentation. Pour les deux types de fibres, les meilleurs résultat sont été obtenus grâce au traitement par plasma. Ce traitement a consisté à déposer un revêtement homogène de tétravinylsilane à la surface des fibres de basalte et de lin, ce qui a permis une augmentation significative de l’adhérence fibre/matrice, ouvrant ainsi la voie à la prochaine génération de composites hybrides plus respectueux de l’environnement et utilisables pour des applications semi-structuralesGlobal awareness of environmental issues has resulted in the emergence of “green” composites, in which natural fibres are used to replace synthetic ones. However, in semi-or structural applications, it can be inconvenient to use composites based on natural fibres. A possible solution to this problem is the development of hybrid composite materials, combining together plies of natural and synthetic fibres. In this framework, the aim of this research project was to develop basalt-flax fibre hybrid composites with a view to obtaining more environmentally friendly composites for semi-structural applications. Hybrid composites were produced through vacuum infusion molding with epoxy matrix.For comparison purposes, 100% flax fibre composites and 100% basalt fibre composites were also manufactured. A quasi-static and dynamic mechanical characterization showed that the hybridization allows the production of a composite with intermediate mechanical performances compared to those possessed by flax and basalt composites. However, the damage analysis has revealed the need to optimize the fibre/matrix interface adhesion quality, in order to increase the mechanical properties of the resulting hybrid composites. For this reason, different surface modification treatments have been specifically designed and investigated for flax and basalt fibres. Flax and basalt fibres were treated by the physical process of Plasma Enhanced Chemical Vapor Deposition. Flax fibres were also subjected to two chemical treatments using enzymatic species and supercritical CO2. The effects of the surface modification treatments on the thermal stability, morphology and mechanical properties of flax and basalt fibres have been investigated. The degree and extent of fibre/matrix adhesion were analyzed by micromechanical fragmentation tests on monofilament composites. The adhesion quality between fibres and both epoxy and vinylester matrices has been assessed in terms of critical fragment length, debonding length and interfacial shear strength. High-resolution μ-CT has been used to support the analysis of the damage mechanisms during fragmentation tests. For both flax and basalt fibres, the best results were obtained after the plasma polymer deposition process. This process was able to produce a homogeneous tetravinylsilane coating on the surface of basalt and flax fibres, which resulted in a significant increase in the fibre/matrix adhesion, thus paving the way for the next generation of more environmentally friendly hybrid composites for semi-structural applications
26
Maenz, Torsten. "Spritzgießtechnische Herstellung duroplastgebundener Dauermagnete." Universitätsverlag der Technischen Universität Chemnitz, 2017. https://monarch.qucosa.de/id/qucosa%3A23550.
Повний текст джерелаАнотація:
Kunststoffgebundene Dauermagnete kommen bereits seit einem dreiviertel Jahrhundert in diversen Anwendungen zum Einsatz. Dabei werden die gängigen Kunststoffverarbeitungsverfahren wie beispielsweise Spritzgießen, Extrudieren, Pressen und Kalandrieren angewandt. Ähnlich zu der Aufteilung in der Verarbeitung von herkömmlichen Kunststoffen, werden auch für die kunststoffgebundenen Dauermagnete nur selten duroplastische Matrixmaterialien im Spritzgießverfahren eingesetzt. Dabei bringt gerade diese Werkstoffklasse hervorragende Eigenschaften mit sich, die eine Verbesserung der Eigenschaften von kunststoffgebundenen Dauermagneten zur Folge haben können. Neben der Medien- und Temperaturbeständigkeit dieser Werkstoffklasse spielt dabei auch deren Viskosität eine bedeutende Rolle für diese Anwendung. Im Rahmen der vorliegenden Arbeit soll geprüft werden, ob der Einsatz duroplastischer Matrixmaterialien zu einer Verbesserung der Eigenschaften kunststoffgebundener Dauermagnete führen kann. Hierfür werden
anisotrope Magnetpartikel in den Kunststoff eincompoundiert und während der Verarbeitung im Spritzgießverfahren orientiert. Dies geschieht durch ein integriertes Magnetfeld im Spritzgießwerkzeug. Insbesondere sollen der Einfluss des Matrixmaterials, der Partikelgeometrie, der Fließrichtung sowie des Richtfeldes auf die Partikelorientierung untersucht werden. Zusammen mit grundlegenden analytischen Untersuchungen der Ausgangsmaterialien sollen abschließend Richtlinien für eine Bauteilauslegung definiert und erste Ansätze
für eine Simulation der magnetischen Bauteileigenschaften erarbeitet werden.Polymer bonded magnets are used for different applications for over 70 years yet. These materials are produced within known polymer processing procedures as injection molding, extruding, compression molding and calendaring. However, as for standard plastics thermoset materials are seldom used in injection molding even though they show great potential regarding temperature and media resistance as well as in terms of a low viscosity. These properties could be of use in case of polymer bonded magnets. Within this work the use of thermoset matrix materials for polymer bonded magnets should be evaluated and thus their properties shall be improved. Therefore anistotropic magnetic particles will be incorporated in the thermoset matrix and they will be oriented during the injection molding process which requires a magnetic field in the cavity during processing. Especially the influences of the matrix material, the particle geometry, the flow direction and the aligning field on the particle orientation should be investigated and together with fundamental analytical procedures guidelines for engineering of parts should be generated as well as first approaches for a simulation of the part properties shall be given.
27
IQBAL, NAHID. "CORE SHELL POLY (DIMETHYLSILOXANE) - EPOXY MICROSPHERE AS IMPACT MODIFIER FOR EPOXY THERMOSETES." Thesis, 2013. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15711.
Повний текст джерелаАнотація:
We report a two-step method for preparation of core shell elastomeric microspheres (CSR) by suspension polymerisation route and demonstrate its potential as an effective impact modifier for thermosetting epoxy resin. The first step involves suspension addition curing of siloxane macromonomer in the presence of platinum based hydrosilylation catalyst. The effect of reaction parameters on the particle size distribution was determined and the elastomeric microspheres were subsequently coated to prepare core-shell (PDMS-epoxy) microspheres. Epoxy composites containing varying amounts of microspheres (3-10 %w/w) were prepared and the effect of coating on the mechanical properties, both in terms of quasi-static as well as dynamic properties were evaluated. The mechanical properties were found to improve at low loadings (≤ 5 % w/w), and the presence of an epoxy coating on the PDMS in the CSR led to improved dispersion, which was evident from its improved mechanical properties. The charpy impact strength increased by 148 % on introduction of core shell PDMS - epoxy (5% w/w). Morphological studies revealed that the roughness of the fractured surface increased due to introduction of microspheres. In contrast to the PDMS containing composites, where the microspheres were removed entirely due to impact loading, the fractured surface of CSR containing composites revealed the presence of broken microspheres, which is a direct evidence of improved adhesion between the elastomeric phase and the epoxy matrix. A representative schematic of the entire process is shown in figure below.
28
Wang, Charng-Shiuan, and 王長炫. "Polyetherimide/Epoxy thermoplastic/thermoset polymer alloy." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/22702317178603945342.
Повний текст джерелаАнотація:
碩士國立交通大學
應用化學系
81
In the thermoplastic/thermoset polymer alloy of PEI/Epoxy, the content of accelerator in the sytem is able to control the curing rate of the thermoset epoxy. When the curing rate is above a critical level, the thermoplastic PEI resin oringinally dissolved in the pre-cured epoxy monomer is being trapped within the epoxy network and can not diffuse out of the epoxy matrix to form a separate phase, a homogeneous polymer alloy is formed. Inhomegeneous polymer alloy can be formed with PEI separated as spherical particles if the epoxy curing rate is below the critical level. Both types of polymer alloys can improve the epoxy toughness significantly by different toughening mechanisms. The homogeneous polymer alloy fractures by a mechanism similar to the unmodified epoxy except larger crack tip plastic zone during crack initiation. In the phase separated polymer alloy, the PEI particles act as stress concentrators to initiate multiple shear nduced cracks and also function as cracki terminators.
29
DENG, GONG-JUN, and 鄧公駿. "Epoxy/Phenoxy thermoset/thermoplastic polymer alloy." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/41508889558995593203.
Повний текст джерела
30
Marotta, Angela. "Renewable furan-derived epoxy thermosets and nanocomposites for coating applications." Tesi di dottorato, 2018. http://www.fedoa.unina.it/12479/1/Renewable_Furan-Derived.pdf.
Повний текст джерелаАнотація:
Research on bio-based polymers is rapidly increasing in last years, pushed by growing environmental and economic concerns, as well as by the uncertainty about future availability of finite petrochemical resources. Sustainability is a keyword in this process. In this frame, products that are respectful towards the environment, including eco-compatible building blocks and additives, are now researched to replace petroleum-based polymers with those derived from naturally occurring feedstocks.
Epoxy resins are very versatile thermosetting polymers, extremely resistant to corrosion, moisture and chemicals, with good adhesive strength toward most materials (wettability) and low shrinkage upon curing. Due to their high glass transition temperatures and excellent mechanical strength, epoxy resins are widely employed in a broad range of applications, such as electronics, structural adhesives, aerospace composites and protective coatings.
More than two-thirds of epoxy resins nowadays are based on diglycidyl ether of bisphenol A. In this industry the trend to replace petrol-derived materials with bio-based ones is related also to the necessity to substitute the Bisphenol A (BPA), a controversial building block recognized as an endocrine disrupter and reprotoxic substance. In particular in application as coating, the use of BPA results in hazard for customers of food and beverage products packed into containers treated with epoxy resins. The effects of human body contamination caused by BPA are diabetes, cardiovascular diseases, altered liver enzymes and reproductive apparatus damages. For these reasons, this molecule has been banned in many countries for the manufacturing of child products, and in France and Canada from all the materials in direct contact with food. The necessity to develop new epoxy resins results therefore urgent.
Bio-derived molecules since now developed show the most various chemical structure, each of them producing different properties of final polymers. Peculiar characteristic shown by epoxy resins are related to the aromatic structure of its components. Aromatic molecules present in natural feedstock are mainly derived from lignin, one of the principal constituents of natural cell walls. However, to extract aromatic moieties from lignin, difficult and energy consuming processes are required. A valuable replacement of aromatic molecules, easily recoverable from glucose, are furanic molecules; their validity has been supported by several studies.
In the light of the above, the work here presented is focused on production of furanic bio-based epoxy resins as potential substitute of DGEBA in can coating industry. The complete cycle of the material has been studied: the synthesis of furanic epoxy monomers and epoxy thermosets, the characterization of their chemical and physical properties (study of curing kinetics, mechanical and thermal properties). Furthermore, the application of bio-based epoxy thermosets as cans internal lining has been evaluated. Experimental results demonstrated that the obtained resins have good potential to be proposed as good alternatives to the traditional BPA-containing epoxy resins.
31
Chou, Ming-Hsuan, and 周明璿. "Synthesis and properties of epoxy thermosets based on phosphinated multifunctional active ester." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/34353242805544753057.
Повний текст джерелаАнотація:
碩士國立中興大學
化學工程學系所
105
The traditional epoxy resin has a high polarity and high dielectric properties, and no flame retardant effect. In order to enhance the flame retardancy of the cured product, the phosphorus-containing structure is introduced into the hardening agent. Bisphenol A under acid catalysis with DOPO to obtain the phosphorus phenolic monomer. Now high frequency communication needs, with the active ester for modification, so that with the curing of epoxy resin can produce ester exchange can effectively reduce the generation of secondary alcohols, reducing the polarity of the cured product. The synthetic hardener and epoxy resin HP7200, CNE, DGEBA curing, from the thermal properties, dielectric properties, and the moisture absorption to do the analysis. It can be seen from the measured dielectric properties that the dielectric constant (3.02~2.71) and the loss tangent (0.008~0.017) can be successfully reduced by the increase of the active ester and there is a tendency to decrease in the moisture absorption(1.93~1.36).
32
Luo, Yu-Shun, and 羅裕舜. "Preparation and Characterization of Porous Epoxy Thermosets via Chemically Induced Phase Separation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/d2sj4a.
Повний текст джерелаАнотація:
博士國立臺北科技大學
工程科技研究所
99
Epoxy thermosets were prepared from a commercial epoxy resin, D.E.R. 331 cured with a tertiary amine, 2,4,6-tris-(dimethylaminomethyl) phenol (DMP-30) in the presence of a solvent, diisobutyl ketone (DIBK). During the curing process, the polymerization resulted in an increase in the molecular weight of polymer and a decrease in its solubility in DIBK; the solution thus phase-separated, usually referred to as chemically induced phase separation (CIPS). The phase separation formed solvent rich phase that then became interconnected pores after the removal of DIBK. By varying the content of DIBK from 32 to 40 vol.% , the epoxy thermosets with interconnected pores were prepared, of which surface pore size ranging from 0.20 to 2.33 μm, overall porosity from 0.41 to 0.60, and ethanol permeability from 10 to 4717 L/(m2．h．bar). The glass transition temperatures of the epoxy thermosets, determined by differential scanning calorimetry, were all higher than 100oC. The thermal stability of the porous epoxy thermosets were further investigated by thermal gravimetry analysis. It was found that temperatures of 5% weight loss, were higher than 350oC. A novel and simple method for producing epoxy thermoset with controlled surface morphology is demonstrated in this study. The epoxy thermosets were made via stepwise polymerization of a mixture of epoxy resin, D.E.R. 331, and diethylene triamine in diisobutyl ketone (DIBK). Both the surface and bulk morphology of the cured polymers are dependent on the solvent fraction of the reactive solution. With higher than about 30 vol.% of DIBK, the chemically induced phase separation, CIPS, occurred during polymerization, and closed spherical pores, about 4 μm in diameter, appeared in the bulk of the cross-linked polymers, which increased to about 4.5, and 9 μm when the solvent was increased to 40, and 50vol.%, respectively. The surface morphology of the epoxy thermosets might be different from that in the bulk. Smaller pore size or dense skin was formed via the CIPS process, which can be tailored by covering the reactive solution with different contacting films during cure. The competition between the solvent-rich and polymer-rich phase absorbed onto the surface of contacting film could change the surface morphology. Therefore, the porous epoxy thermosets having similar bulk morphology could be prepared with a variety of surface structures. In order to understand the different mechanism of phase separation between the porous epoxy thermosets cured by DMP-30 and DETA. A DSC and rheometer were further used to monitor the phase separation process. The DSC curve for the solution cured with DMP-30 shows a phase separation behavior much different from that cured with DETA. For the system with DMP-30, there are two main exothermic peaks on the DSC curve, the first peak is considered to be contributed a quaternary ammonium alcoholate formed via the initiation reaction of the epoxy and tertiary amine groups, and the second one from the chain propagation proceeds by the active site via the anionic polymerization. While, for the system with DETA, via a step-wise polymerization only one exothermic peak was found during the curing process. The rheological results as indicated, the D.E.R. 331/DMP-30 system after phase separation, its storage modulus and loss modulud curves was closing mean that the polymer-rich domain was easier to gel and the domain size of polymer rich or solvent rich was small. Different structures of the cured epoxy thermosets have been observed in the epoxy resin, D.E.R. 331 cured with DMP-30/DETA curing agents mixture, in the presence of a solvent, diisobutyl ketone (DIBK) via chemically induced phase separation. The epoxy thermosets increase in pore size of cross-section and decrease in pore size of surface with increasing amount of DETA. Moreover, have the dense structure of the surface epoxy thermoset, while the content of DMP-30/DETA was increased to 1/0.4. When mixture of curing agent DMP-30/DETA was 1/1 and 0/1, the pore structure of epoxy thermoset transform from interconnected pore into close pore mophology.
33
TRIPATHI, MANORAMA. "INVESTIGATING THE INFLUENCE OF MICROENCAPSULATED HEALING AGENTS ON THE PROPERTIES OF EPOXY THERMOSETS." Thesis, 2017. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16140.
Повний текст джерелаАнотація:
The primary motivation behind the present research work is to study the effect
of inclusion of healant loaded microcapsules on specific properties (thermal,
structural and mechanical) of a representative epoxy thermoset. In addition, we also
explore alternate chemistry for introducing self healing functionality in epoxy
composites. Two distinct healing systems have been investigated, namely
cycloaliphatic epoxy and unsaturated polyester. The healants were encapsulated in
urea-formaldehyde microcapsules by adopting an in-situ dispersion polymerization
route and in polystyrene shell through solvent evaporation process. The effect of
operating parameters particularly stirring speed on the particle size distribution has
been studied. Under optimal conditions, the core content of the epoxy loaded
microcapsuleswas found to be 65 ± 4%for microcapsules prepared by dispersion
polymerization route and 38 ± 2%for microcapsules prepared using solvent
evaporation route.
It is to be noted that the healing efficiency is strongly influenced by the
internal microstructure of the microcapsule and we also developed an analytical
model for predicting the amount of healant released in the event of microcapsule
rupture. In microcapsules possessing “reservoir” type microstructure, the healant
exists as a single droplet, where the entire content is expected to be released upon
rupture. On the other hand, in monolithic microcapsules, the healant is dispersed in
the form of discrete micro-droplets, and only the healant available within the cracked
microcapsule is expected to be released and cause healing. Our model predicted that
significantly lower amounts of healant is released in monolithic microspheres in
comparison to reservoir microcapsules, especially when the micro-droplet dimensions
and core content, both are low.
V
Triethylenetetramine (TETA) hardener was encapsulated by adopting two
methods, namely interfacial polymerization and physical entrapment technique. The
effects of experimental parameters, namely reaction temperature (50-75°C), stirring
speed (400-700 rpm) and epoxy: amine concentration ratio (10:1.2-10:4.3) on the
microcapsule properties was investigated. A polymeric surfactant was used to
stabilize the suspension in order to modulate the particle size distribution of the
resultant microcapsules. Highest encapsulation efficiencies resulted when the
reaction medium was maintained at 70°C under a stirring speed of 600 rpm, while
maintaining an epoxy: amine ratio of 10:3.2. The microcapsule dimensions and core
content could be tailored, following the interfacial polymerisation route. Under
optimal conditions, spherical microcapsules with 100 % yield and 12% core content
were obtained.
Physical entrapment approach was also explored for the immobilisation of
amine hardener in mesoporous silica. For this purpose, mesoporous silica (SBA-15)
was synthesised using polymer-templated technique and employed as a substrate for
immobilization. Vacuum infiltration of TETA led to its entrapment within the porous
structure of SBA-15 with loadings as high as 5g/g, which could be attributed to
hydrogen bonding and acid–base interactions.
The curing kinetics of self-healing epoxy compositions was investigated by
non-isothermal differential scanning calorimetric (DSC) studies. Epoxy loaded
microcapsules and immobilised amine was dispersed into epoxy resin, and cured
using TETA. DSC studies revealed the autocatalytic nature of epoxy curing, which
remained unaltered due to addition of the fillers responsible for introducing self
healing functionality. The kinetic parameters of the curing process were determined
using both Friedman and Kissinger–Akahira–Sunose (KAS) method. The activation
VI
energy at different degree of conversion (E ) was found to decrease with increasing
degree of cure ( ). Although urea-formaldehyde possess secondary amine
functionalities, which have the potential to react with the epoxy groups, no significant
differences in the curing kinetics of the base resin were observed.Kinetic parameters
were used to predict the curing behaviour of compositions at higher heating rates
using KAS method. As expected, the onset curing temperature (Tonset) and peak
exotherm temperature (Tpeak) of epoxy shifted towards higher temperatures with
increased heating rate; however introduction of fillers do not affect these
characteristic temperatures significantly. Also, the overall order of reaction does not
vary significantly. The results suggest that although 2° amino groups are available
with the urea-formaldehyde (UF) resin, these do not directly participate in the curing
reaction, as the primary amino groups in TETA are more easily accessible.
To evaluate the effect of self healing additives on the mechanical properties
and healing efficiency, epoxy composites containing UF and PS microcapsules (5
30%, w/w) were prepared by room temperature curing and their mechanical
behaviour and healing efficiency was studied under both quasi-static and dynamic
loadings. The tensile strength, modulus and impact resistance of the matrix was found
to decrease with increasing amount of microcapsule in the formulation, the
detrimental effect being less pronounced for polystyrene microcapsules due to its
monolithic internal microstructure. Morphological investigations on the cracked
surface revealed features like crack pinning, crack bowing, microcracking and crack
path deflection, which were used to explain the toughened nature of microcapsule
containing epoxy composites.
VII
Healing efficiency was quantified in terms of the ratio of impact strength
before and after healing. For the purpose of validation of the developed analytical
model, composites were prepared using epoxy encapsulated microcapsules with
varied internal structures. Ni and Cu-imidazole complexes were prepared for use as
latent hardeners for epoxy. Both the imidazole-metal complexes could effectively
cure the epoxy released from within the microcapsules in the event of damage
followed by thermal treatment. In line with our predictions, the extent of healing was
much lower in the case of samples containing monolithic microcapsules. At 20% w/w
microcapsule loadings, healing efficiencies close to 60% was observed upon
introduction of reservoir type microcapsules, while under similar loadings, only 10%
healing could be evidenced in the presence of monolithic microcapsules.
For reservoir type microcapsules, complete healing (efficiency ~ 100±2%)
could be effected at 30% microcapsule loading, in the presence of metal imidazole
complexes. In comparison, the complete healing was evidenced at relatively lower
microcapsule loading (20%, w/w) when amine immobilised SBA-15 was used.
The potential of encapsulated unsaturated polyester resin (USP) towards
introduction of healing functionality was also explored. USP was encapsulated in
urea-formaldehyde shell and polystyrene shell by dispersion polymerization and
solvent evaporation technique respectively both resulting in the formation of free
flowing microcapsules. Calorimetric studies confirmed the chemical activity of the
encapsulated USP, which spontaneously polymerised in the presence of a free radical
initiator, 2,2‟-Azobis(2-methylpropionitrile) (AIBN), at temperature as low as 80°C.
Temperature triggered healing of epoxy-microcapsule composites was performed at
110° C and healing efficiency was quantified as the ratio of impact strength of healed
and virgin specimens. The same was found to increase with increasing amount of
VIII
microcapsule in the formulation and reached a maximum (100 ± 2%) at 20% (w/w)
loading. Fractographic analysis of the surface revealed the flow pattern of chemically
active polyester resin from the ruptured microcapsules, which subsequently cured in
the presence of AIBN available within the matrix.
34
Chen, Yu-Jane, and 陳育甄. "Synthesis and characterization of the thermoset maleimide-epoxy and bismaleimide resins." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/86207682028880630165.
Повний текст джерелаАнотація:
碩士中原大學
化學工程研究所
91
英文摘要 A novel compound (4-maleimidophenylglycidylether, MIE) containing both maleimido and epoxide groups was synthesized as use as monomers for preparation of new thermosetting resins. The chemical structure of MIE was characterized with FTIR and 1H NMR. Thermosetting resins showing high glass transition temperatures (>210 ℃), good thermal stability (higher than 350 ℃), and excellent flame retardance (LOI = 38) were obtained from curing MIE with conventional epoxy curing agents of DDM and DICY. The kinetics of the curing reactions was also studied. Reacting MIE with various biphenol compounds gave a convenient approach to prepare bismaleimide compounds having epoxy linkages between the maleimide groups. These bismaleimides exhibited good organosolubility, low melting points, and wide processing windows, consequently referred their good processibility. It was found that incorporating silicon group into the bismaleimide resulted in superior thermal stability of the cured bismaleimides.
35
Tsai, Kun-Ling, and 蔡昆霖. "Synthesis of phosphorus-containing multifunctional epoxy resin and thermal properties of the resulting thermosets." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/94863378360763921449.
Повний текст джерелаАнотація:
碩士國立中興大學
化學工程學系所
102
Based on phosphorus-containing polymer P5, and polymer P5-N3 which was prepared by P5 and polyformadehyde, we produced epoxy resins P5-EP and P5-N3-EP. The structures of P5-EP and P5-N3-EP were confirmed by FTIR and NMR spectra. By checking epoxy equivalent weight with theoretical value, we produced high purity epoxy resins. Then, P5-EP and P5-N3-EP were curing with amine、benzoxazine and phenol novolac. Properties such as glass transition temperature, coefficient of thermal expansion, thermal decomposition temperature, and flammability of the resulting epoxy thermosets were evaluated and compared with each other. Because of high epoxide functional group numbers , the resulting of P5-N3-EP thermoset shows high Tg, high char yield and excellent flame retardancy.
36
Chang, Sheng-Lung, and 張勝隆. "Facile Synthesis of Benzoxazines and Diamines for High-performance Epoxy/benzoxaine Thermosets and Polyimides." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/qv4t5t.
Повний текст джерелаАнотація:
博士國立中興大學
化學工程學系所
99
In this thesis, we revealed facile strategies to prepare benzoxaines and diamines for high-performance epoxy/benzoxazine thermosets, polyimides and polyimide/silica hybrids. The detailed studies were discussed as follows: First, three aromatic diamine-based benzoxazines were successfully prepared by a facile, clean, one-pot procedure from 1,4-phenylenediamine (1), 4,4’-diaminodiphenyl ether (2), and 4,4’-diaminodiphenyl methane (3), respectively. Their structures were confirmed by NMR spectra and single crystal diffractogram. The effect of the reactivity of diamines on the purity of the resultant benzoxazines was discussed. The resultant benzoxazines were applied as hardeners for cresol novolac epoxy (CNE). The processing window, the latent curing characteristic, and the miscibility of benzoxazine/CNE systems were discussed. Compared with diamines (1 and 3), (1 and 3)-based benzoxazines show latent curing characteristic as epoxy hardeners, and wide processing windows can be obtained. Compared with diamine (2) which is immiscible with CNE in the molten state, benzoxazine (5) shows good miscibility with CNE. Dynamic mechanical analysis shows the Tgs of the benzoxazine/CNE thermosets are as high as 242-243 oC. Thermogravimetric analysis shows the outstanding thermal stability of the resultant thermosets. Secondly, Two phosphinated diamines, 1-(4-aminophenyl)-1-(3-t-butyl-4-aminophenyl) -1- (6-oxido-6H -dibenz <c,e> <1,2> oxaphosphorin-6-yl)ethane (1) and 1-(4-aminophenyl) -1-(3-methxoy-4-aminophenyl)-1-(6-oxido-6H -dibenz <c,e> <1,2> oxaphosphorin-6-yl)ethane (2), were prepared via a facile, one-pot reaction of DOPO, 4-aminoacetophenone and 2-tertbutylaniline or 2-anisidine in the catalysis of p-toluenesulfonic acid. Based on diamine (1-2), a series of asymmetric polyimides (3-4) were prepared in NMP/xylene by high-temperature solution polymerization. The ortho t-butyl or methoxy substitution increases the steric and electronic repulsion, resulting in reduced intramolecular interaction. Therefore, transparent polyimides can be obtained. In addition to good transparency, polyimides 3-4 display flexibility, good organo-solubility, high Tg values (310-384 oC), good dimensional stability (23-48 ppm/oC), and moderate thermal properties (Td5wt%, nitrogen: 461-477 oC; air, 456-474 oC). Thirdly, A hydroxyl diamine, 1-(4-aminophenyl)-1-(3-hydroxyl-4-aminophenyl)-1-(6-oxido-6H -dibenz <c,e> <1,2> oxaphosphorin-6-yl)ethane (1), was prepared via a facile, one-pot procedure. Based on diamine (1), a series of hydroxyl polyimides, polyimides (2), were prepared in NMP/xylene by high-temperature solution polymerization. Polyimides (2) are readily soluble in some organic solvents, and can be solution casted into flexible and creasable films. Polyimide/SiO2 hybrids were prepared based on the sol-gel reaction of tetraethoxysilane (TEOS) with polyimide (2e), which was prepared from (1) and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). The hydroxyl group on the backbone of the polyimides could provide organic-inorganic bonding, and transparent and flexible polyimide/SiO2 films with TEOS content up to 40 wt % can be obtained without any coupling agent. TEM data showed the formation of well-dispersed SiO2 clusters. The optical and thermal properties of polyimide 2e were improved via the incorporation of silica.
37
Hsueh, Yu-Heng, and 薛育珩. "A Study on Toughen Property of Epoxy-Anhydride Thermosets with an Aliphatic Long Chain Hardener." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/bjy6b5.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
材料科學與工程系
105
In this study, an anhydride-typed Long Chain Hardener with aliphatic chains will be used to improve epoxy fracture toughness and other mechanical properties. For the sake of chemical toughening,the liquid phase can be homogeneous before curing reaction start and no phase separation happen in epoxy-anhydride network. We use FTIR, NMR, MASS to determinate Long Chain Hardener functional groups and aliphatic chains in the structure of the distribution.Then use DSC, TGA, DMA to analyze processing conditions and thermal properties, the mechanical properties of the use of tensile test, three-point bending and IZOD impact test to confirm the impact strength. We found that the structure with soft segments will decrease the glass transition temperature. However the tensile, bending performance improved and impact resistance also increased. This is caused by chemical structure and cross-linking density. The experimental results also show that the soft chains can enhance its fracture toughness in the glassy state without losing its main mechanical properties.
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Whalen, Casey Allen. "Dispersion and Characterization of Nickel Nanostrands in Thermoset and Thermoplastic Polymers." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10686.
Повний текст джерелаАнотація:
Nickel Nanostrands (NiNS) are nano-particles that are highly branched and have a high aspect ratio. These particles show promise as excellent additives to composites when electrical conductivity is desired. Unfortunately, there is very little research done on dispersing powdered NiNS in various polymer matrices. This thesis covers the research in dispersing NiNS in three separate polymer systems, and related composite processing and characterization. An aromatic polyimide (CP2) is first used as a thermoplastic matrix and attempts to incorporate NiNS via an in-situ processing technique concurrent with in-situ polymerization are detailed. Epoxy is then used as a representative thermoset where the NiNS are dispersed in the resin before a hardener is added. The last polymer tested is thermoplastic Polyvinylidene Fluoride (PVDF). NiNS are introduced to this polymer in a solution mixture. Once dispersed, the PVDF solution is heated until the solvent evaporates leaving a PVDF melt containing NiNS, which is subsequently cooled. Samples of all three polymer nano-composites are created and dispersion is observed with an optical microscope. Using DSC, DMA and dielectric spectroscopy, thermal, mechanical and electrical properties are measured and analyzed.
Results for the CP2 nano-composites showed that during the cure phase, the NiNS settled to the bottom of the films resulting in a non-dispersed composite. This result highlighted the difference between NiNS and other more conventional nano-particles, namely that the NiNS are larger and heavier, therefore are not 'locked into' a dispersed state by the polymer chains. Several techniques were investigated for dispersing NiNS in the epoxy matrix. A method without solvent was shown to be the most effective and resulted in a well-dispersed nano-composite that showed increases in electrical conductivity and dielectric constant as NiNS concentration increases. Enhancement in storage modulus was observed above the composite's Tg as well. PVDF nano-composites also showed good dispersion and a general increase in electrical properties. Below Tg, storage modulus decreases at first before a slight recovery with increasing NiNS. Beyond Tg, the opposite effect is observed. FTIR measurements for the PVDF were also taken and showed no significant changes in the polymer morphology with additions of NINS.
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(8704884), Matthew N. Korey. "Tannic Acid: A Key To Reducing Environmental Impacts of Epoxy." Thesis, 2020.
Знайти повний текст джерелаАнотація:
Epoxy thermosets have revolutionized the coating, adhesive, and composite industries but the chemicals from which they are synthesized have significant effects on the environment and human health not only pre-cure but also after crosslinking has occurred. Many flame retardants (FR), hardeners, and other additives used in epoxy thermosets are synthesized from petroleum-based monomers leading to significant environmental impacts at the industrial scale. Various bio-based modifiers have been developed to circumvent these environmental concerns; however, dispersing biologically-based molecules into the system without tradeoffs with other properties, especially mechanical properties and the glass transition temperature, has proven challenging. Tannic acid (TA) is a bio-based high molecular weight organic (HMWO), aromatic molecule. Although biologically sourced, TA is a pollutant in industrial wastewater streams, and there is desire to find applications in which to downcycle this molecule after extraction from these streams. The unique properties that make TA applicable in a variety of applications including leather tanning, burn wound treatment, and water purification are desirable in epoxy thermosets. In this study, we propose TA as an alternative additive for epoxy. We will uncover the usefulness of TA as an epoxy hardener and as a FR additive. Previous work uncovered that TA could be dispersed in epoxy with weights up to 37 wt%, the highest loading level achieved in literature for this molecule. Using TA as an epoxy hardener resulted in materials that had glass transition temperatures at and above 200⁰C. Using TA as a FR additive resulted in intumescent-behavior previously unseen with TA in epoxy. Chemical functionalization with acetic anhydride further enhanced the behavior resulting in a reduction of the peak heat release rate of the materials by 80%. Ongoing research in the use of solvent, metal ion complexation, and water-borne epoxy containing TA will additionally be explored. The result of this work indicated that TA showed significant promise as a biologically-based functional additive as a flame retardant and epoxy hardener and could reduce environmental impact of many currently available products.
40
Tsai, Yi-Lin, and 蔡易霖. "Synthesis and properties of epoxy thermosets based on (2,6-dimethyl phenylene oxide) active polyester and phosphinated crosslinkable active polyester." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/97801529135134440160.
Повний текст джерелаАнотація:
碩士國立中興大學
化學工程學系所
105
In order to meet the requirement for high-speed communication, epoxy thermosets used in electronic components need continuous update in dielectric and thermal properties. Epoxy thermosets with both low dielectric and high thermal properties are a nowadays target. It is known that active ester type of epoxy hardener can enhance dielectric properties by converting the high polarity secondary alcohol to ester group. However, it leads to the reduction of the thermal properties. For the sake of maintaining the thermal properties, this work particularly study on the active polyester with enhancing dielectric and thermal characteristics. In part 1 of this work, a series of active polyesters, SA-PE, are synthesized from the phenol-end capped oligo(2,6-dimethyl phenylene oxide) (SA90) and diacid chloride by high-temperature polymerization. The epoxy thermosets based on SA-PE and commercial epoxy resins show low dielectric properties. In part 2 of this work, a series of active polyester, A-PE, with phosphinated and allylic linkage are synthesized from a allylic-containing phosphinated biphenol (Allyl-DMP) and dicarbonyl dichloride by interfacial polymerization. The epoxy thermosets based on A-PE and commercial epoxy resins exhibit high thermal properties. In part 3 of this work, the allylic linkage in A-PE was epoxide by meta-chloroperoxybenzoic acid (mCPBA) to obtain EP-PE with both the active ester and epoxide unit. EP-PE was self-cured to obtain high-performance epoxy thermosets without other epoxy resins or hardeners
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lLai, Ching, and 賴慶. "Usage of beads-milled waste silicon sawdust in Epoxy thermoset for advanced anticorrosion coatings application upon metallic substrate." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/f37xn6.
Повний текст джерелаАнотація:
碩士中原大學
化學研究所
106
The main target of this dissertation is to prepare the composite coatings containing waste silicon sawdust, followed by applied as an anticorrosion coatings. First, the waste silicon sawdust provided by company was beads-milling process with Zr beads in the diameter of 5 mm and 10 mm. Subsequently, the as-prepared silicon sawdust was introduced into epoxy resin coating by performing the thermally ring-opening polymerization reactions. A series of electrochemical corrosion measurements were performed to investigate the as-prepared composite coatings containing epoxy resin and waste silicon sawdust. It should be noted that the anticorrosion studies of composite coatings have drawn three conclusions: (1) Composite coatings showed better anticorrosion performance than neat epoxy coating. (2) At same feed loading, composite coatings containing grounded silicon sawdust showed better anticorrosion performance than that containing non-grounded sawdust. (3) Composite coatings with higher loading of silicon sawdust exhibited better anticorrosion performance. Keywords: silicon sawdust, epoxy, ball mill, anti-corrosion
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Detwiler, Andrew Thomas. "Aspects of network formation and property evolution in glassy polymer networks." 2011. https://scholarworks.umass.edu/dissertations/AAI3482611.
Повний текст джерелаАнотація:
Experimental and theoretical characterization techniques are developed to illuminate relationships between molecular architecture, processing strategies, and physical properties of several model epoxy-amine systems. Just beyond the gel point partially cured networks are internally antiplasticized by unreacted epoxy and amine which leads to enhanced local chain packing and strain localization during deformation processes. Additional curing causes the antiplasticization to be removed, resulting in lower modulus, density, yield stress, and less strain localization. Physical and mechanical probes of network formation are discussed with respect to several different partially cured model epoxy-amine chemistries. The non-linear fracture energy release rate and the molecular architecture of virgin and healed epoxy networks are related through an effective crack length model. The inelastic component of the fracture energy release rate is attributed to the failure of network strands in a cohesive zone at the crack tip. Data from fracture and healing experiments are in good agreement with the model over more than three orders of magnitude. Changes in the shape of the process zone and deviation from planar crack growth cause deviations from the model for the toughest networks tested. Double network epoxies are created from stoichiometric blends of an epoxy resin cured sequentially with aliphatic and aromatic amine curing agents. Unreacted epoxide and aromatic amine functionality antiplasticize the partially cured materials. The thermal and mechanical properties of the fully cured networks vary according to composition. No evidence of phase separation is observed across the entire composition and conversion range. However, the breadth of the glass transition in the double networks increases due to the difference in the molecular stiffness of the two curing agents. Techniques are developed to monitor the evolution of residual stresses and strength in complex multicomponent epoxy-amine based coatings. The evolution of properties is attributed to loss of volatile small molecules from the coatings. The stresses that develop in biaxially constrained membranes are monitored through mechanical excitation. The strength of the membranes is determined by monitoring the size and shape of center cracks. This fracture analysis technique allows the evolution of stresses and toughness of the materials to be monitored simultaneously.