Made available in DSpace on 2014-10-09T12:36:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:48Z (GMT). No. of bitstreams: 0 / Pasta de cimento é um material comum em repositórios para rejeitos radioativos, atuando como material estrutural e de imobilização. Sua utilização como material de preenchimento em um repositório tipo poço tubular profundo para fontes seladas, no entanto, requer um maior tempo de vida útil do material. O conhecimento de seu comportamento em longo prazo é necessário para garantir a segurança da instalação em milhares de anos. O presente trabalho avaliou as alterações na pasta de cimento induzidas por fatores de degradação, como ataque de agentes agressivos, alta temperatura e presença de campo de radiação. Corpos de prova (cps) de pasta de cimento foram submetidos a ensaios acelerados de degradação e os efeitos deletérios foram avaliados por meio de ensaios de resistência mecânica, variação dimensional, lixiviação/penetração de íons, DRX, TGA e MEV. Observou-se que a hidratação dos cps foi beneficiada pela imersão (em água destilada ou em solução salina) e alta temperatura, resultando em uma resistência maior. O armazenamento à seco prejudicou a hidratação, mantendo a resistência mais baixa. O tempo de imersão e a irradiação não foram capazes de alterar a mineralogia e a resistência da pasta de cimento. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-10-22T16:54:02Z No. of bitstreams: 0 / Made available in DSpace on 2015-10-22T16:54:02Z (GMT). No. of bitstreams: 0 / A utilização de radiofármacos no diagnóstico de doenças do organismo humano tem aumentado de forma significativa nas últimas décadas. O crescente desenvolvimento de novos reagentes liofilizados (RL) para a preparação de radiofármacos, embora proporcionem uma maior variedade para o mercado de radiofármacos, deixa evidente uma das lacunas na pesquisa radiofarmacêutica: a identificação de produtos de degradação. No presente trabalho, foram identificados os principais produtos de degradação dos RL de ácido 2,3-Dimercaptosuccínico (DMSA) e Etilenodicisteína Dietil Éster (ECD) utilizando as técnicas de cromatografia líquida de alta eficiência com Detecção por Arranjo de Diodos (HPLC-DAD) e cromatografia líquida acoplada à espectrometria de massas de múltiplos estágios (LC-MSn). Realizou-se o estudo de degradação forçada do RL de DMSA e do RL de ECD nas condições de estresse hidrolítico, fotolítico, oxidativo e termodegradação. As análises foram realizadas em equipamento HPLC-DAD Shimadzu e espectrômetro de massas Bruker Daltonics. Todas as análises foram desenvolvidas utilizando coluna cromatográfica Shim-Pack VP-ODS (150 mm x 4,6 mm; 5 μm). O DMSA apresentou tempo de retenção de 5,58 minutos e m/z 204,8. A hidrólise ácida do DMSA não apresentou produtos de degradação. O perfil de degradação do DMSA após hidrólise alcalina apresentou três picos cromatográficos com características mais apolares que o DMSA. No espectro de fragmentação do íon de m/z 204,8 (MS2) pode-se observar a presença do fragmento de m/z 172,9, correspondente ao aduto sodiado de ácido mercaptosuccínico (MSA); e o fragmento de m/z 139,0 (MS3), correspondente ao aduto sodiado do ácido fumárico. O íon estanho (Sn) apresentou-se coordenado ao DMSA em todos os produtos de degradação após hidrólise alcalina do RL de DMSA. As amostras submetidas à hidrólise neutra não apresentaram degradação. Nos estudos de fotólise do DMSA, o íon de m/z 267,1 pode ser identificado como o ácido diacetil dimercaptosuccínico (BATSA). O íon de m/z 127,1 foi associado ao ácido hidroximetil fosfônico e observado nos estudos de oxidação. A termodegradação do DMSA e do RL de DMSA, não apresentou uma relação de decaimento da concentração do DMSA em função do tempo. Quanto ao RL de ECD, foi observado o ECD protonado em 5,55 minutos (m/z 325,6). As análises por LC-MSn do ECD sob hidrólise alcalina mostraram que o pico com tempo de retenção de 1,71 minutos foi identificado como o íon protonado do EC ([M+H]+) em m/z 269,2. Os picos com tempo de retenção de 3,34 e 3,69 minutos foram identificados como o íon protonado do ECD na forma monoéster (ECDM). A degradação alcalina do RL de ECD apresentou os íons de m/z 441,9 (ECD-Sn) e m/z 737,9 ([ECD2+Sn]-C2H2-2H). ECD monoester monoácida (ECDM) de m/z 295,2; ECD oxidado de m/z 323,5; ECD oxidado com duas pontes dissulfeto de m/z 389,1 e dímero de ECD de m/z 645,9 foram observados da degradação oxidativa. Conclui-se que as análises por HPLC-DAD e LC-MSn podem ser utilizadas no estudo de estabilidade de RL, identificando suas impurezas e produtos de degradação. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientador: Pilar Rodriguez de Massaguer / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-04T02:36:41Z (GMT). No. of bitstreams: 1 NolascoJunior_Jonas_M.pdf: 917952 bytes, checksum: 1c082a25920f5c8390a73425551d86ef (MD5) Previous issue date: 2005 / Resumo: Nesta pesquisa é proposto um processo de tratamento térmico do mosto, com máxima preservação do conteúdo em açúcares fermentescíveis (sacarose, glicose e frutose), a fim de promover a inativação térmica de seus contaminantes bacterianos e por extensão os da fermentação alcoólica. Com esse objetivo foram examinadas as cinéticas de degradação térmica da sacarose, glicose, frutose e açúcares redutores totais (ART) (110 ¿ 140ºC) e também dos esporos de B. stearothermophilus (98 ¿ 130ºC), esporulado termo-resistente contaminante típico de mosto. Todos os fatores termodegradáveis estudados apresentaram cinéticas de destruição térmicas não-lineares de forma que o índice de redução decimal (D), obtido por regressão linear, não foi representativo da velocidade de inativação térmica, e assim as cinéticas foram analisadas mediante modelos não lineares que permitiram obter as constantes de velocidade de inativação (k). Seguidamente utilizando um gráfico tipo Arrhenius a energia de ativação Ea foi determinada e o valor de z foi obtido. As curvas de sacarose remanescentes obtidas durante estudo da sua hidrólise térmica, foram ajustadas por modelos logísticos que se mostraram apropriados para descrever ombros planos e caudas finais nas curvas cinéticas. A energia de ativação e valor z obtidos foram 112,32 kJ/mol e 26,99ºC, respectivamente. Essa reação se mostrou praticamente equimolecular quanto às hexoses produzidas. As curvas de concentração de ART vs tempo remanescentes foram ajustadas por modelos logísticos bipopulacionais, apropriados em casos em que o processo global é descrito por duas frações de compostos, as hexoses glicose e frutose, que se degradam em velocidades diferentes e apresentam ombros e caudas. Os valores de energia de ativação obtidos para a frutose e glicose foram bem próximas: 140,37 kJ/mol e 140,23 kJ/mol, respectivamente. Os valores z obtidos foram 21,59ºC e 21,61ºC. Quanto às velocidades de degradação a frutose apresentou velocidade 9 vezes maior do que a da glicose. A suspensão de esporos se mostrou heterogênea em resistência. A temperatura influenciou a forma das curvas de sobreviventes, para os esporos de B. stearothermophilus ATCC1518. Nas temperaturas mais baixas, as curvas de inativação térmica apresentaram ombro plano, passando por comportamento de modelos de frações lineares consecutivas, e finalmente na temperatura mais elevada apresentou modelo linear com eliminação da fração termo-sensível. Os valores de energia de ativação e z obtidos foram 249,52 kJ/mol e 11,48ºC, respectivamente. O processo térmico para inativação dos contaminantes do mosto foi definido após o decantador, onde foram quantificados grandes grupos microbianos em amostras coletadas de Usinas situadas em regiões de clima e umidade distintas. A concentração máxima de esporos termofílicos produtores de acidez plana foi de 9x101esporos/ml de mosto em Usina localizada em região quente e úmida enquanto um valor de 4 esporos/ml de mosto foi encontrado em Usina localizada em região de clima seco e com predominância de solo com baixa capacidade de retenção de água. Foi determinada a letalidade do processo de decantação para os contaminantes do caldo de cana e mosto através da determinação da história térmica mínima detectada no ponto mais frio de dois decantadores industriais. Baseado no tempo de residência médio e na temperatura mais fria detectada foi possível estimar que a decantação produz, em média, 4,0 x 106 reduções decimais da população de Lactobacillus fermentum e apenas 0,14 reduções decimais nos esporos de B. stearothermophilus. Baseado no conhecimento da cinética dos principais fatores termodegradáveis foi definida uma região de tratamento térmico que se extende dos 114 a 140ºC e de 3000 a 4 segundos. Graficamente essa região é um triangulo delimitado, abaixo pela reta correspondente a 5 reduções decimais dos esporos de B. stearothermophilus e acima pela reta correspondente à preservação de 98,7% dos ART do mosto. O nível de preservação de 98,7% dos ART foi escolhido pela precisão das análises usadas na determinação dos mesmos (1,3%). Qualquer processo térmico dentro dessa região será capaz de satisfazer o requisito de 5 reduções decimais dos esporos de B. stearothermophilus e preservação de 98,7% dos ART do mosto. A prática desse processo térmico implica na adoção de uma estratégia preventiva no controle da contaminação da fermentação em oposição às estratégias corretivas baseadas no uso de antibióticos que se pratica nas Usinas de Açúcar e Álcool Brasileiras / Abstract: In this research is proposed a thermal treatment process for sugar cane must with maximum retention of fermentable sugar (sucrose, glucose and fructose), to promote a thermal inactivation of its bacterial contaminants and therefore, those of alcoholic fermentation. With this objective were examined the thermo degradation kinetics of sucrose, glucose, fructose, total reducing sugars (TRS) (110 ¿ 140ºC) and also B. stearothermophilus spores (98 ¿ 130ºC), a typical thermo resistant sporulated contaminant of musts. All thermo degradable factors showed non-linear thermal destruction kinetics due to this the D value, obtained for linear regression, could not be used, thus the kinetics were reported by Arrhenius model, obtaining the reaction rates (k), Activation Energy (Ea) and the z value through out Ea values. Sucrose remaining curves obtained as a function of time during its thermal hydrolysis, were fitted by logistic models which are suitable to describe flat shoulders and ending tales in the kinetic curves. Activation Energy and z value were 112,32 kJ/mol and 26,99°C, respectively. This reaction showed to be equimolecular in regard to the produced hexoses. TRS remaining curves vs time were adjusted by logistic bipopulational models, suitable when the overall process presents two fractions, the hexoses glucose and fructose, with different degradation rates with shoulders and tales. Ea and z values for fructose and glucose were quite close: 140,37 kJ/mol, z of 21,59°C and 140,23 kJ/mol, z of 21,61°C, respectively. As far as degradation rates are concerned, fructose showed to degrade 9 times faster than glucose. Spores suspension showed heterogeneity in thermal resistance. Temperature affected the shape of survival curves for B. stearothermophilus ATCC1518 spores. At lower temperatures, it showed flat shoulder, passing through consecutive linear fraction models behaviors, and finally at higher temperatures followed linear model with elimination of the thermo-sensible fraction. Ea and z values were 249,52 kJ/mol and 11,48°C respectively. A thermal process for sugar cane must contaminant inactivation was defined after the decanter, where microbiological quantification of various microbial groups was carried out on samples from sugar cane mills located in region with different climate and humidity conditions. The maximum thermophilic flat-sour spores count was of 9 x 101 spores/ml of must and was originated from a sugar cane mill located at the warmest and most humid region, while a count of 4 spores/ml of must was found in a plant with dry climate and with soil of low capability for water retention. Decanters lethality of must contaminant was determined based on the minimum detected thermal history in two industrial equipments. Applying the average residence time with this thermal history, it was estimated that the decantation results, on average, 4,02*106 log reductions of Lactobacillus fermentum and only 0,13 log reductions in the counting of B. stearothermophilus spores. Based on the kinetic knowledge of the thermo degradable major factors it was established a thermal process region from 114 to 140C and 3000 to 4 seconds. Graphically, this region is a triangle delimited by the line for 5 log reductions of B. stearothermophilus (lower limit), and the line for 98,7% retention of the must TRS. This preservation level was adopted considering the accuracy of the sugar analysis methodology (1,3%). Any thermal process within this region will be able to satisfy the requirement of 5 log reductions for B. stearothermophilus and 98,7% retention of must TRS. The implementation of this thermal process implies in the adoption of a preventive strategy in the contamination control of the fermenting process, opposite to the corrective strategies currently applied based on antibiotics, which is common practice in Brazilian Sugar Canes mills / Mestrado / Ciência de Alimentos / Mestre em Ciência de Alimentos

La demande actuelle du marché du transport en matériaux composites à matrice polymère est en augmentation importante afin de remplacer les pièces aujourd’hui fabriquées en alliages métalliques par des matériaux plus légers et performants. Actuellement couramment utilisés, les composites thermodurcissables présentent l’inconvénient de ne pas être recyclables. Aussi, un des objectifs du projet « Résines idéales » durant lequel cette thèse a été réalisée est de mettre au point de nouveaux composites à matrice thermoplastique, doués de propriétés équivalentes. Parmi celles-ci, le comportement au feu est un enjeu essentiel pour leur développement et l’objectif de cette thèse est de développer de nouveaux systèmes retardateurs de flamme pour des matériaux composites thermoplastiques à fibres continues. Dans un premier temps, un screening des retardateurs de flamme phosphorés potentiellement efficaces a été effectué. L’étude de l’influence du renfort taffetas sur la stabilité thermique et le comportement au feu a également été réalisée (cône calorimètre, IOL, UL94). Ensuite, afin d’améliorer le comportement au feu, et en particulier, de satisfaire aux normes feu aéronautiques (les plus exigeantes), nous avons étudié des mélanges binaires et ternaires de retardateurs de flamme constitués du RF phosphoré sélectionné et d’autres charges : alumine, hydroxyde d’aluminium (ATH), graphite expansé, et 9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide (DOPO). Dans chaque cas, la stabilité thermique et le comportement au feu ont été caractérisés et discutés / The present demand of polymer-matrix composite materials in the transport market is significantly increasing, to replace the work-pieces actually manufactured in metal alloys, the polymer-matrix composite being lighter and more performant. Thermoset composites are currently and widely used however this kind of composites presents a severe drawback due to their non- recyclable character. One of the objectives of the “Résines idéales” project and of this thesis is to develop new composites made from thermoplastic matrix, endowed with similar properties. Among them, the fire behavior is a major challenge and the aim of this work is to develop new flame retardant systems for thermoplastics composites reinforced with continuous fibers. Firstly, we have performed a screening of potentially effective phosphorus flame retardants. Also, we have studied the influence of the reinforcement taffetas on the thermal stability and fire behavior. For that, various tests have been performed such as cone calorimeter, LOI and UL-94. Then, to improve the fire behavior and particularly to satisfy the aeronautical fire standards (the most challenging), we have studied binary and ternary mixtures of flame retardants constituted by the selected phosphorus flame retardant and other additives: alumina, aluminum hydroxide (ATH), expanded graphite and 9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide (DOPO). In each case, the thermal stability and fire behavior have been characterized and discussed

La durabilité des matériaux employés en génie civil est remise en question par le vieillissement physico-chimique de ces matériaux pouvant engendrer des dégradations significatives qui peuvent mettre en péril la stabilité des structures du génie civil. Pour pallier à certains inconvénients des bétons hydrauliques, l'utilisation des matériaux composites à l'instar des bétons de résine, qui possèdent des qualités remarquables par rapport aux matériaux de construction conventionnels, s'avère très intéressant.À l'heure actuelle, les freins majeurs quant aux développements des bétons résines sont d'une part le coût de la résine dont le taux varie, selon l'application industrielle, de 5% à 25% et d'autre part leurs comportements aux températures élevées et au feu puisque les liants dans ces bétons sont des substances organiques qui résistent beaucoup moins à la chaleur que les matières inorganiques. L'objectif de l'étude est de favoriser le développement des bétons résines par la diminution du taux de la résine en optimisant les constituants du béton et l'amélioration de leurs ténues aux températures élevées par l'ajout des additions tout en assurant des performances mécaniques raisonnables. L'optimisation de la formulation du béton est menée sur deux étapes ; la première vise à optimiser le squelette granulaire (sable 0/4 et Gravier 4/10, silico-calcaires) expérimentalement en confrontant les résultats à ceux issus du modèle d'empilement compressible. La deuxième étape vise à optimiser la fraction massique du liant époxydique (6%, 9%, 13% et 16%) sur la base des essais de caractérisation mécaniques et physiques. Le deuxième objectif de l'étude a était menée par l'ajout des ignifugeants appartenant à deux familles différentes c'est-à-dire les hydroxydes de métal et les produits phosphorés inorganiques. Les propriétés physiques, thermiques et mécaniques des bétons additionnées et témoins, avant et après exposition à un cycle de chauffage-refroidissement de la température ambiante à une température de consigne de 100°C, 150°C, 200°C, 225°C et 250 °C avec une vitesse de montée fixée à 0.5°C/min, ont été évaluées par les techniques de caractérisation usuelles en plus des essais d'analyses chimiques et thermiques.Cette étude aboutit à la formulation d'un béton optimal en terme de composition et à évaluer l'effet de l'addition des ignifugeants surtout sur les propriétés thermiques et mécaniques.Mots clés : béton de résine, optimisation, température élevée, ignifugeants, propriétés mécaniques, propriétés physiques, propriétés thermiques. / The material used in civil engineering applications must be re-evaluated because of their physicochemical ageing which can generate significant damages and hence put the stability of civil engineering structures in danger.The replacement of the hydraulic concrete by composite materials as the polymer concrete which offer higher properties compared to conventional construction materials seems to be very interesting. At the present time, the major restrain for the development of polymer concrete are on one hand the cost of the polymer whose ratio varies according to the industrial applications between 5% and 25%, and on the other hand their behaviour when exposed to high temperatures or fire since the resin acting as binder in these polymer concretes are organic substances which are more sensitive to heat than the inorganic matters as cement.The aim of this study was to help the development of polymer concrete by optimizing the formulation and improving their behaviour when exposed the high temperatures by incorporating additions while keeping acceptable mechanical performances.The optimisation of the formulation is done in two steps; the first step consists of optimising the aggregates content (Natural River sands 0/4 mm and crushed gravels 4/10 mm). Experimental results are compared to those given by means Compressible Packing Model. The second step consists of optimizing the amount of polymer (6%, 9%, 13% et 16%) based on mechanical and physical tests.The second aim of this work was fulfilled by the incorporation of two flame retardants belonging to metal hydroxide and phosphorous components types. Physical, thermal and mechanical properties of concretes with or without flame retardant, before and after heating-cooling cycle from ambient temperature to exposure temperature of 100°C, 150°C, 200°C, 225°C et 250 °C with a rate of 0.5°C/min, are evaluated by common characterisation tests besides chemical and thermal ones. This study has leading to obtaining an optimum polymer concrete and evaluates the effect of flame retardant particularly on the thermal and mechanical properties.Keywords: polymer concrete, optimization, high temperatures, flame retardant, mechanical properties, physical properties, thermal properties.

Tato dizertační práce se zabývá studiem morfogeneze dimethakrylátových sítí. V práci byly využity zjednodušené systémy založené na monomerech, které bývají typicky využívány jako složky matric pryskyřičných kompozitních materiálů využívaných v oblasti záchovné stomatologie. Kinetika a mechanismy formování polymerních sítí byly studovány především s ohledem na strukturu jednotlivých monomerů, jejich vzájemný molární poměr a koncentraci iniciačního systému využitého pro radikálovou polymeraci. Vypočtené profily konverze funkčních skupin a reakčních rychlostí byly využity jako základ pro pochopení a interpretaci mechanismů morfogeneze sítí a porovnání se známými modely. Dále byla studována kinetika termické degradace, která je s morfologií vytvrzených sítí přímo spjata. V rámci takto charakterizovaných systémů byla stanovena teplotní závislost dynamického modulu a byl popsán vztah mezi supra-molekulární strukturou dimethakrylátových sítí a jejich viskoelastickou odezvou v daném teplotním rozmezí. Kinetika polymerace byla studována pomocí diferenční kompenzační foto-kalorimetrie (DPC) a infračervené spektroskopie (FTIR). Proces termické degradace byl analyzován pomocí termo-gravimetrické analýzy (TGA). Viskoelastické parametry byly charakterizovány pomocí dynamicko-mechanické analýzy (DMA). Reaktivita jednotlivých systémů je přímo odvozena od molekulární struktury monomerů, která ovlivňuje mobilitu reagujících složek v průběhu polymerace. Kinetika polymerace je řízena především difúzí, přičemž její rychlost je dána tuhostí monomerní páteře, koncentrací funkčních skupin a vlivem fyzikálních interakcí. Omezená mobilita rostoucích řetězců, postranních funkčních skupin i samotných monomerů vede k monomolekulární terminaci makro-radikálů a omezení stupně konverze funkčních skupin. Vzhledem k tomu, že k zásadnímu omezení mobility dochází již v počáteční fázi polymerace, tj. v bodu gelace, je případná termodynamická nestabilita vedoucí k fázové separaci polymerujícího systému potlačena a proces kopolymerace je ve své podstatě náhodný. To bylo prokázáno i prostřednictvím identifikace jedné teploty skelného přechodu u charakterizovaných kopolymerů. Heterogenní charakter morfogeneze je spjat s rozdílnou reaktivitou postranních funkčních skupin. V počátečních fázích polymerace dochází k propagaci reakcí postranní funkční skupiny s radikálem na stejném rostoucím řetězci, což vede ke vzniku tzv. primárního cyklu. Pravděpodobnost cyklizace souvisí především s flexibilitou monomerní páteře. Heterogenita polymerace je charakterizována vznikem vnitřně zesítěných struktur, tzv. mikrogelů, a jejich následným spojováním. Tuhost monomeru naopak přispívá k vyšší efektivitě zesítění a více homogenní morfologii vytvrzené sítě. Heterogenita dimethakrylátových sítí se odráží v mechanismu termické degradace, přičemž přítomnost strukturně odlišných domén vede k rozkladu ve dvou krocích. Průběh soufázového modulu a teplota skelného přechodu korelují s tuhostí polymerních sítí, efektivitou zesítění a přítomností fyzikálních interakcí, které vyztužují strukturu sítě nad rámec kovalentního zesítění. Heterogenní morfologie sítí se projevuje rozšiřováním spektra relaxačních časů. Experimentální data jsou v kvalitativní shodě s existujícími numerickými modely popisujícími kinetiku radikálové polymerace multifunkčních monomerů.

This diploma thesis investigated thermal stability and the degradation of hyaluronan (HA) in HA with a molecular mass of 90–130 kDa and in HA with a molecular mass of 1 500–1 750 kDa. The following methods were used for the research: rheology, SEC-MALLS, TGA and DSC. Low-molecular HA was subject to time dependency of degradation investigation, where it was dried at a temperature of 90 °C for a period of 30 minutes and 60 minutes prior to the preparation of the solutions itself. High-molecular HA was investigated not only from the point of view of time but from the point of view of temperature dependency of degradation as well. In the case of investigating the time dependency of degradation, high-molecular HA was dried at a temperature of 75 °C at a time range from 15 minutes to 120 minutes prior to the preparation of the solutions. During the preparation of the solutions for discovering the temperature dependency of degradation, the high-molecular HA was then dried for a period of 30 minutes at a temperature range from 60 °C to 90 °C. For low-molecular HA, thermal stability was proven. Therefore, there is no decrease in the molecular mass and the solutions did not demonstrate a significant decrease of viscosity. For high-molecular HA, thermal stability was not proven. Degradation due to the temperature of drying as well as the time of drying occurred, which was demonstrated by a significant decrease in molecular mass and viscosity of the solutions. While in the case of using a drying temperature of 60 °C, a decrease in the molecular mass occurred by approximately 5 %, the molecular mass decreased by approximately 20 % at a drying temperature of 90 °C compared to undried HA. Due to this reason, high-molecular HA was also further investigated by means of the TGA method, where the decrease of humidity of HA samples in relation to the drying temperature was observed. The DSC method was also used. The objective of the DSC method was to find out temperatures, at which evaporation of humidity contained in an HA sample in relation to its form (undried HA, dried HA and lyophilized HA) occurs. This method further finds out the heat necessary to evaporate humidity from an HA sample. To conclude this research, the results obtained for high-molecular HA were compared with the results of other drying processes – lyophilized proved to be a very gentle drying method because a decrease in the molecular mass for lyophilized HA compared with undried HA almost did not occur.

L’utilisation croissante des matériaux composites à matrice thermoplastique dans l’industrie aéronautique passe par une meilleure compréhension de leur comportement mécanique lors d’une exposition à un flux rayonnant (conséquence d’un incendie). Cette étude, portant sur le comportement thermo-mécanique de stratifiés tissés quasi-isotropes composés d’une matrice PPS renforcée par des fibres de carbone, se divise en 3 parties. Tout d’abord, la décomposition thermique du matériau et l’évolution de ses propriétés mécaniques avec la température sont étudiées. Ces données permettent ensuite d’appréhender le comportement de ces matériaux soumis à des chargements combinés (flux rayonnant et chargement mécanique en traction ou en compression, de type monotone à rupture et en fluage). La dernière partie vise à identifier les paramètres matériau nécessaires pour la simulation thermo-mécanique aux échelles macroscopique et mésoscopique. / The increasing use of thermoplastic-based composite materials in the aeronautical industry requires a better understanding of their mechanical behavior when exposed to radiant heat flux (consequence of a fire exposure). This study, which examines the thermo-mechanical behavior of quasi-isotropic woven laminates composed of PPS reinforced with carbon fibers, is divided into 3 parts. First, the thermal decomposition of the material and the evolution of its mechanical properties with temperature is studied. These data help to understand the behavior of these materials subjected to combined loads (radiant heat flux and tensile or compressive loadings). The last part aims to identify the material parameters necessary for thermo-mechanical simulation at macroscopic and mesoscopic scales.

In unserem alltäglichen Leben nehmen Kunststoffe eine immer größere Rolle ein. Die organische Struktur dieser Materialien bedingt die Brennbarkeit derselbigen und birgt somit eine Gefahr, die allgegenwärtig ist. Flammschutz von Polymeren ist daher eine wichtige Eigenschaft. Der Markt an Flammschutzadditiven ist bereits sehr breit gefächert. Allerdings gibt es nur wenig Studien, die systematisch Struktur und Flammschutzwirkung betrachten. So war es das Ziel dieser Arbeit, durch die Untersuchung zweier systematisch variierter Polymergruppen Struktur-Eigenschafts-Beziehungen zu entwicklen, die das Verständnis von Flammschutzadditiven erweitern. Die erste Gruppe bestand aus Polyestern mit einem gleichbleibenden Polymerrückrat an dem phosphorhaltige Seitenketten systematisch variiert wurden. In der zweiten Gruppe wurde das Polymergrundgerüst bei gleichbleibendem Substituenten variiert. Die Strukturen wurden umfassend hinsichtlich ihres Abbaus untersucht, so das durch Korrelation von Abbauverhalten und erarbeiteten Abbaumechanismen Zusammenhänge zwischen der nativen Polymerstruktur und dem Flammschutzverhalten gefunden werden konnten. Es lässt sich nachweisen, dass das Hauptabbaumaximum fast vollständig durch die Polymergrundkette dirigiert wird. Der Substituent hat wenig Einflauss darauf, womit sich die Möglichkeit ergibt Flammschutzadditive gezielt and das Abbaumaximum des zu schützenden Matrixpolymers anzupassen. Die strukturelle Veränderung des phosphorhaltigen Substituenten hingegen ermöglich es das Flammschutzadditv in seiner Wirkungsweise, also Aktivität in der Gasphase oder kondensierten Phase, anzupassen. Sehr wesentlich, besonders mit Blick auf die Rückstandbildung, ist das Zusammenspiel zwischen Substituent und Polymerrückgrat. Bei geeigneter Wahl aliphatischer und aromatischer Anteile lassen sich so Flammschutzadditive herstellen, die einerseits gut zu verarbeiten sind, andererseits aber auch einen möglichst hohen Rückstand erzeugen. Mit Kenntnis dieser Struktur-Eigenschafts-Beziehungen ist es zukünftig möglich, polymere Flammschutzadditive zielgerichteter zu entwickeln. So lässt sich das Additiv in seiner Wirkung nicht nur an das Matrixpolymer anpassen, sondern auch an die primären Brandgefahren in dessen Endanwendung. Eine Under-the-hood-Anwendung im Automobilbau fordert andere Flammschutzeigenschaften als die Verwendung im häuslichen Küchenbedarf.

Conventional microelectronic and power electronic packages based on Si devices usually work below 150°C. The emergence of wide-bandgap devices, which potentially operate above a junction temperature of 250°C, results in growing research interest in high-density and high-temperature packaging. There are high-temperature materials such as encapsulants on the market that are claimed for capability of continuous operation at or above 250°C. With an objective of identifying encapsulants suitable for packaging wide-bandgap devices, some of commercial high-temperature encapsulants were obtained and evaluated at the beginning of this study. The evaluation revealed that silicone elastomers are processable for various types of package structure and exhibit excellent dielectric performance in a wide temperature range (25 - 250°C) but are insufficiently stable against long-term aging (used by some manufacturers, e.g., P²SI, to evaluate polymer stability) at 250°C. These materials cracked during aging, causing their dielectric strength to decrease quickly (as soon as 3 days) and significantly (60 - 70%) to approximately 5 kV/mm, which is below the value required by semiconductor packaging. The results of this evaluation clearly suggested that silicone needs higher thermal stability to reliably encapsulate wide-bandgap devices. Literature survey then investigated possible methods to improve silicone stability. Adding fillers is reported to be effective possibly due to the interaction between filler surface and polymer chains. However, the interaction mechanism is not clearly documented. In this study, the effect of Al₂O₃ filler on thermal stability was first investigated by comparing the performance of unfilled and Al₂O₃-filled silicones in weight-loss measurements and dielectric characterization. All test results on composites filed with Al₂O₃ micro-rods indicated that thermal stability increased with increasing filler loading. Thermogravimetric analysis (TGA) test demonstrated that the temperature of degradation onset increased from 330 to 379°C with a 30 wt% loading of Al₂O₃ rods. In isothermal soak test, unfilled and 30-wt%-filled silicones lost 10% of polymer weight in 700 and 1800 hours, respectively. The dielectric characterization found that both Weibull parameters, characteristic dielectric strength (E₀, representing the electric field at which 62.3% of samples are electrically broken down) and shape parameter (β, representing the spread of data. The larger the β, the narrower the distribution) can reflect the thermal stability of polymers. Both of them were influenced by microstructure evolution, to which β was found to be more sensitive than E₀. The characteristic dielectric strength of unfilled silicone decreased significantly after 240 hours of aging at 250°C, whereas that of Al₂O₃/silicone composites exhibited no significant change within 560 hours. The shape parameter of Al₂O₃-filled silicone decreased slower than that of unfilled silicone, also indicating the positive effect of Al₂O₃ micro-rods on thermal stability. Improved thermal stability can be explained by restrained chain mobility caused by interfacial hydrogen bonds, which are formed between hydroxyl groups on Al₂O₃ surface and silicone backbone. In this study, the effect of hydrogen bonds was investigated by dehydrating Al₂O₃ micro-rods at high temperature in N₂ to partially destroy the bonds. Removal of hydrogen bonds impaired thermal stability by increasing the initial weight-loss rate from 0.025 to 0.036 wt%/hour. The results explained the importance of interfacial hydrogen bond, which effectively reduced the average chain mobility, hindered the formation of degradation products, and led to higher thermal stability. The main discoveries of this study are listed below: 1. Al₂O₃ micro-rods were found to efficiently improve the thermal stability of silicone elastomer used for high-temperature encapsulation. 2. Characteristic dielectric strength and shape parameter obtained from Weibull distribution reflected the change of material microstructure caused by thermal aging. The shape parameter was found to be more sensitive to microscale defects, which were responsible for dielectric breakdown at low electric field. 3. Hydrogen bonds existing at filler/matrix interface were proven to be responsible for the improvement of thermal stability because they effectively restrained the average chain mobility of the silicone matrix. / Ph. D.