京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第20478号 / エネ博第347号 / 新制||エネ||69(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 / (主査)教授 坂 志朗, 教授 塩路 昌宏, 准教授 河本 晴雄 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第23535号 / エネ博第426号 / 新制||エネ||81(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 / (主査)教授 河本 晴雄, 教授 石原 慶一, 教授 川那辺 洋 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

Made available in DSpace on 2015-05-14T13:21:12Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2114816 bytes, checksum: 3cd21721a8386d2947be773c9c59d4a8 (MD5) Previous issue date: 2010-09-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The efficiency of an engine during the combustion process depends, among other factors, on the viscosity of the fuel. A high viscosity decreases the fuel volatilization resulting in an incomplete combustion. The biodiesel added to diesel fuel leads to improvements in their characteristics with respect to combustion gases emissions to the atmosphere. Sudden drops in temperature are responsible for increasing the viscosity and crystallization of fatty esters of biodiesel components causing damage in the engine. This concerns to both, biodiesel and mineral diesel, because the late is composed by saturated hydrocarbons which tend to form crystals at low temperature. To minimize this limitation biodiesel from fish oil blended with diesel, can improve the fluid dynamic properties of the fuel in different conditions of evaluation. GC-MS analysis revealed the presence of 31.57% of methyl linoleate as the major component of biodiesel from fish. The infrared spectra indicated the efficacy of transesterification reaction to obtain the methyl ester. From the viscosity curves as a function of temperature, was observed that the binary mixtures shown a similar profile to that of diesel, a sharp reduction in viscosity with increasing temperature in the range 5-15 ° C, this event is evidenced in the TMDSC cooling curves in the melting process followed by the formation of crystals, melting temperature and freezing, which were correlated with flow techniques. The gradual addition of biodiesel do not cause significant changes in the fluidity and fog points. To pure biodiesel was observed a sharp decrease of temperature, explained by the presence of (Z)-unsaturated esters in its composition, which obstruct the packing between molecules. Increasing the concentration of biodiesel in the diesel matrix gives a slight increase in consumption and viscosity of the fuel remaining so within the limits allowed. In conclusion fish oil biodiesel/diesel blends are a excellent alternative for using in diesel cycle engines. / A eficiência de um motor no processo de combustão depende, dentre outros fatores, da viscosidade do combustível. Uma alta viscosidade diminui a volatilização implicando em uma combustão incompleta. O biodiesel adicionado ao diesel mineral induz em melhorias nas suas características no que diz respeito às emissões dos gases resultantes da combustão para a atmosfera. Quedas bruscas na temperatura ambiente são responsáveis pelo aumento da viscosidade e pela cristalização de ésteres graxos componentes do biodiesel interferindo no funcionamento do motor. Este problema não é exclusivo do biocombustível, pois o diesel convencional, composto por hidrocarbonetos saturados, em baixas temperaturas tendem a formar cristais. Para minimizar essa limitação o biodiesel oriundo de óleo peixe em misturas com o diesel, pode melhorar as propriedades fluidodinâmicas do combustível em diferentes condições de avaliação. As análises de CG-EM evidenciaram a presença de 31,57% de linoleato de metila, como componente majoritário do biodiesel de peixe. Os espectros na região do infravermelho indicaram a eficácia da reação de transesterificação e obtenção do éster através da rota metílica na presença no catalisador básico (KOH). A partir das curvas de viscosidade em função da temperatura, observou-se que as misturas binárias apresentam perfil semelhante ao do diesel, com redução brusca na viscosidade com o aumento da temperatura na faixa de 5 a 15 ºC. Esse evento é evidenciado nas curvas de resfriamento TMDSC no processo de fusão seguido de formação de cristais, temperatura de fusão e congelamento, que foram correlacionadas com as técnicas de fluxo. A adição gradual de biodiesel não provocou alterações significativas nos pontos de fluidez e névoa. Para o biodiesel puro observou-se acentuada diminuição da temperatura, e isso é explicado pela presença de ésteres insaturados em geometria Z em sua composição, o que dificulta o empacotamento entre as moléculas. O aumento da concentração do éster na matriz do diesel confere um aumento no consumo e na viscosidade do combustível, permanecendo dentro dos limites permitidos (ANP). A partir dos resultados, conclui-se que o biodiesel de óleo de peixe e as misturas diesel/biodiesel são uma alternativa para o uso em motores do ciclo Diesel.

Made available in DSpace on 2015-05-14T13:21:48Z (GMT). No. of bitstreams: 1 parte1.pdf: 1824546 bytes, checksum: 63f6c49a25027174e176be6f2e35704e (MD5) Previous issue date: 2010-07-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The Brazilian biodiesel, whatever the source of their raw materials must meet some physical and chemical parameters that ensure their quality. A major problem associated with the use of biodiesel, especially prepared with castor oil, is its high viscosity that is outside the limit set by the ANP, becoming viable as fuel, only when used as a blend to diesel or other biodiesel with lower viscosity. The soybean biodiesel presents a high percentage of esters of polyunsaturated fatty acids being more susceptible to oxidation when compared to castor oil biodiesel. Within this context, the blends of ethylic biodiesel from soybean and castor oil (BsMx) in natura and in different storage conditions are promising in the correction of the flow properties and oxidative stability. The GC-MS results confirmed the presence of 42.45% of ethyl linoleate and 85.83% of ethyl ricinoleate for the ethylic biodiesel from soybean and castor oil, as major components, respectively. The infrared spectra showed increased content of castor oil biodiesel in the blend by more intense absorption at 3440.7 cm-1. The presence of ethyl ricinoleate in higher concentration in the blend conditioned the better oxidative stability, therefore, there was a decline in the pour point. Blends with proportions of until 30 and 57% were within the limit established by the ANP for kinematic viscosity and density, respectively. The condition and storage time of 120 days caused changes decreasing induction period and increasing the acidity index, water content and kinematic viscosity, being more evident for samples stored under light. During storage of 120 days, the density, the cold filter plugging point, the cloud point and the pour point were barely affected, with only a slight increase more pronounced for samples stored under light. Blends of ethylic biodiesel from soybean and castor oil allowed the use of oil in the composition of a new biodiesel (BSM) to be blended with diesel oil within the limits established by ANP for viscosity. / O biodiesel produzido no Brasil, qualquer que seja a fonte de sua matéria-prima, deve atender a alguns parâmetros físico-químicos que assegurem sua qualidade. Um dos principais problemas associados com o uso do biodiesel, especialmente o preparado com óleo de mamona, é sua alta viscosidade, encontrando-se fora do limite estabelecido pela ANP, tornando-se viável como combustível apenas quando usado como mistura ao Diesel ou a outro biodiesel de menor viscosidade. Já o biodiesel de soja por apresentar um elevado percentual de ésteres de ácidos graxos poli-insaturados é mais susceptível a oxidação quando comparado ao biodiesel de mamona. Inserido neste contexto, as blendas de biodiesel etílico de soja e de mamona (BSMX) in natura e em diferentes condições de armazenamento, apresentam-se promissoras quanto à correção das propriedades de fluxo e estabilidade oxidativa. Os resultados de CG-EM confirmaram a presença de 42,45% do linoleato de etila e 85,83% do ricinoleato de etila para o biodiesel etílico de soja e mamona, como componentes majoritários, respectivamente. Os espectros de infravermelho mostraram acréscimo do teor de biodiesel de mamona na blenda através da absorção mais intensa em 3440,7 cm-1. A presença do ricinoleato de etila em maior concentração na blenda condicionou a uma melhor estabilidade oxidativa que, por conseguinte, ocorreu um decaimento no ponto de fluidez. Blendas com proporções de até 30 e 57% mostraram-se dentro do limite estabelecido pela ANP para viscosidade cinemática e densidade, respectivamente. As condições e o tempo de armazenamento de 120 dias provocaram variações decrescentes no período de indução e crescentes no índice de acidez, teor de água e viscosidade cinemática, sendo mais evidenciado para as amostras armazenadas na presença de luz. Durante o armazenamento de 120 dias, a densidade, o ponto de entupimento de filtro a frio, ponto de névoa e fluidez praticamente não foram afetados, havendo apenas um leve aumento mais acentuado para as amostras armazenadas na presença de luz. As blendas de biodiesel etílico de soja e mamona permitiram o aproveitamento deste na composição de um novo biodiesel (BSM) para ser utilizado em misturas com óleo Diesel respeitando os limites estabelecidos pela ANP para viscosidade.

The aim of this diploma thesis is to propose a recipe of natural BB-creams with the desired properties (different color shades, that will be suitable for Central European skin type; flow properties, texture, spreadability, stability). The experimental part of the thesis is mainly focused on the development of BB-cream formulas. Several different formulations with diverse dispersion medium (water and aloe vera/water in a suitable ratio) have been proposed, and three different shades of BB-cream have been developed. The flow properties (viscosity) of the samples were measured, accelerated stability tests were realized by using the dispersion analyzer LUMISizer, the obtained results were correlated with the results of stress temperature tests. The results of the rheological analysis showed that the flow properties of the creams are comparable with commercially available preparations. Stress temperature tests have shown that prepared samples remain stable over 4 cycles (12 weeks) of changing storage temperature, accelerated destabilization tests performed by LUMISizer confirmed their stability. The colour coordinates of the developed shades were measured using a spectrophotometer and compared with commercial analogues. Also the questionnaire for sensory evaluation of preparations for more comprehensive analysis of prepared BB-creams was developed. The 25 female respondents of different ages participated in servey. The results of sensory evaluation showed that textural properties of developed creams are satisfactory for potential consumers.

Made available in DSpace on 2015-05-14T13:21:17Z (GMT). No. of bitstreams: 1 Arquivototal.pdf: 1872774 bytes, checksum: cfad5d7593ecbe90fb9fa2cb98560aca (MD5) Previous issue date: 2011-12-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work describes the physical-chemical, oxidative and fluid dynamics properties of Licuri palm nuts biodiesel (Syagrus coronata), in order to make this oleaginous plant an alternative source for biofuel production in the semi-arid climate in the northeastern region of Brazil. It also aims the analysis of blends of soy biodiesel methyl and licuri (BSLx) as a correction of the oxidative stability properties. The methyl transesterification of Licuri and soy oils was produced by basic catalysis, on molar ratio of 1:4,5 and of 1:5,5 respectively, temperature of 40°C (after adding methoxide, the bain-marie was turned off), 1,5% concentration of KOH catalyst. The percentage rate of conversion into methyl esters according to the stoichiometry resulted from the transesterification was 96,65 for the licuri biodiesel methyl and of 94,91 for the soy biodiesel methyl. The samples were later characterized by infrared spectroscopy and by gas chromatography-mass spectrometry. The results from CG-EM confirmed the presence of 51, 43% of methyl linoleate and 37, 40% of methyl laurate in the soy biodiesel methyl and licuri biodiesel, as main components, respectively. The increase of the amount of BML in the blend led to a decrease in kinematic viscosity, in the the dropping point and an increase in oxidative stability. All of the blends stayed within the limits of the ANP, in relation to their physical-chemical and fluid dynamics properties. The engine fuel consumption (L/h) presented the following order: BML<BSL50<BMS, the same order was observed in the mixtures of diesel. / Este trabalho relata as propriedades físico-químicas, fluidodinâmicas e oxidativas do biodiesel de licuri (Syagrus coronata), visando tornar esta oleaginosa uma fonte alternativa de biocombustível no semi-árido nordestino. Objetiva também as análises das blendas de biodiesel metílico de soja e licuri (BSLX) quanto à correção das propriedades de estabilidade oxidativa. A transesterificação metílica dos óleos de licuri e soja ocorreu por catálise básica, na razão molar 1:4,5 e 1:5,5 respectivamente, temperatura 40°C (após a adição do metóxido o banho foi desligado) e concentração 1,5% de catalisador KOH. A taxa percentual de conversão em ésteres metílicos de acordo com a estequiometria da reação de transesterificação foi de 96,65 para o biodiesel metílico de licuri e de 94,91 para o biodiesel metílico de soja. As amostras dos biodieseis foram posteriormente caracterizadas por espectroscopia no infravermelho e por cromatografia gasosa acoplada ao espectrômetro de massa. Os resultados de CG-EM confirmaram a presença de 51,43% do linoleato de metila e 37,40% do laurato de metila para o biodiesel metílico de soja e licuri, como componentes majoritários, respectivamente. O aumento do teor de BML na blenda levou a uma diminuição na viscosidade cinemática, no ponto de fluidez e aumento na estabilidade oxidativa.Todas as blendas se enquadraram dentro dos limites da ANP, em relação às propriedades físico-químicas e fluidodinâmicas. O consumo (L/h) de combustível no motor apresentou a seguinte ordem: BML < BSL50 < BMS, o mesmo comportamento foi observado nas misturas com diesel.

Cette étude concerne l’ajout de billes de verre de dimension variant de 1 à 50 m dans des matrices cimentaires. Les travaux ont comme objectif dans un premier temps la caractérisation des propriétés physiques et rhéologiques à l’état frais des suspensions cimentaires à deux échelles : la pâte de ciment et le mortier. Puis dans un deuxième temps l’étude de l’influence des microbilles de verre sur les propriétés physiques, mécaniques et durabilité du mortier durci. Des séries d’expériences normalisées ont été faites pour caractériser l’influence des billes de verre sur les indicateurs à l’état frais : la consistance et la prise des pâtes de ciment. Les propriétés mécaniques et de durabilité sont quantifiées au jeune âge (de 3 à 28 jours) et à long terme (de 28 jours à 112 jours). L’étude sur les gels d’hydratation et sur la microstructure du mortier durci a été faite à l’aide de la technique de la microscopie électronique à balayage. Des méthodes de caractérisation complémentaires pour examiner la propagation d’onde, la ségrégation et l’étalement ont également été employées. Les résultats obtenus par l’ensemble des essais évaluent le rôle des microbilles de verre sur les comportements des suspensions de pâtes de ciment et du mortier à l’état frais, et du mortier à l’état durci. Ceci met en évidence l’intérêt rhéologique, mécanique et l’effet sur la durabilité des microbilles de verre dans un matériau cimentaire. / The aim of this work is the valorisation of recycled waste materials in cement paste and mortar in order to reuse these resources for replacing natural aggregates in concrete. Our study concerns the use of a microsphere glass powder (MGP) with a particle size from 1 to 50 m into the cement matrix. This experimental work first focuses on the effect of the MGP on the workability properties of fresh cement paste and fresh mortar and on the physical, mechanical and durability properties of mortar. Many standard tests have been conducted for the characterisation of the behavior of the fresh cement paste i.e the consistency and the setting of fresh cement paste. The durability properties at early age (from 3 to 28 days) and at long time (from 28 days to 112 days) have been also quantified. We employed the scanning electron microscopy for the mortar microstructure analysis. Some supplementary tests like the ultrasonic wave propagation, the segregation and the flow properties on the vibrated table have been also used. The primary results have proved the effect of the MGP on the behaviour of the fresh cement paste, fresh mortar and mortar. The presence of MGP showed interesting modifications on the rheology, mechanical and durability properties of the cement system.

Made available in DSpace on 2017-07-21T14:13:05Z (GMT). No. of bitstreams: 1 Amanda Lyra.pdf: 6099284 bytes, checksum: 8701070289c9fd679c58cb469286e18a (MD5) Previous issue date: 2016-02-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The efavirenz is the first choice drug of non-nucleoside reverse transcriptase inhibitors used in the treatment of HIV-1 infections. It belongs to class II of the Biopharmaceutics Classification System and your therapeutic dose is of 600 mg, taken before bedtime due the side effects. With the aim of improve the drug’s bioavailability with possible reduction of side effects, microparticles with Eudragit® L100 or S100 were developed by spray drying. The formulations M1 to M4 were prepared in ethanol:water (50:50, V/V) and M5 to M8 in ethanol:phosphate buffer pH 7.4 (50:50, V/V). Microparticles were obtained with yield (40 - 70%), humidity (1.41 - 5.77%), particle size (2.02 - 4.07 μm) and zeta potential (-61 to -43) suitable. The drug’s quantification was realized by high performance liquid chromatography analytical method developed and validated. The method proved to be specific, linear (r = 0.9997, n = 3), precise, accurate and robust in a range of 8.0 to 50.0 μg.mL-1, with analysis and retention time of 5.0 and 3.5 minutes, respectively. M1 to M4 showed spherical morphology with drug content between 90 - 104%, and M5 to M8 exhibited flattened and distorted morphology with drug content between 67 - 75%. No chemical interactions was observed in the Fourier transformed infrared spectrum for microparticles M1 to M4. However, there enlargement and increased intensity of some bands in the spectra of microparticles M5 to M8, suggesting a modification of chemical bonds. The thermal analysis and X ray diffraction indicated that the incorporation of EFV into the microparticles contributed to the amorphization of the drug. In vitro drug release confirmed the low solubility of the drug in water (22.88%). The microparticles released less than 22% in acid medium promoting higher release at pH 6.8. All formulations evaluated increased the drug solubility and dissolution efficiency, and exhibited biexponential release kinetics according to the applied mathematical models, being interesting strategies to increase the drug’s bioavailability. The M3 accounted for the major release in pH 6.8 (73.69%) and, according to the Korsmeyer-Peppas model showed anomalous transport characteristics (diffusion and erosion of the polymer), while in other microparticles the release process was controlled by diffusion. In in vitro assay the animals subjected to the administration of M3 exhibited less alterations in the biochemical parameters compared to treatment group EFV, suggesting that the microparticles contributed to the reduction of side effects such as increase in cholesterol, LDL, HDL and triglycerides plasmatic levels. It was observed decay in the quantification of pure drug during the period evaluated in the stability study. The microparticles showed no significant changes in the content of EFV during the 180 days. The thermograms showed no difference in the drug melting range and decays of thermogravimetric curves suggesting no formation of new products and consequently loss of stability. The evaluation of Carr index and Hausner factor indicated that M3 showed better flow and compression properties compared to pure EFV, characteristics which can improving the flow and to facilitate industrial routine. / O efavirenz (EFV) é o fármaco de primeira escolha da classe dos inibidores da transcriptase reversa não análogos de nucleosídeo utilizado no tratamento de infecções por HIV-1. Pertence à classe II do sistema de classificação biofarmacêutico e sua dose terapêutica é de 600 mg, tomados antes de dormir devido aos efeitos colaterais. Com objetivo de melhorar a biodisponibilidade do fármaco com possível redução dos efeitos colaterais, foram desenvolvidas micropartículas com Eudragit® L100 ou S100, por spray drying. As formulações M1 a M4 foram preparadas em etanol:água (50:50, V/V), e M5 a M8 em etanol:tampão fosfato pH 7,4 (50:50, V/V). Foram obtidas micropartículas com rendimentos (40 – 70%), umidades (1,41 – 5,77%), tamanhos de partícula (2,02 – 4,07 μm) e potenciais zeta (-61 a -43 mV) adequados. A quantificação do fármaco foi realizada por meio do método analítico por cromatografia líquida de alta eficiência desenvolvido e validado. O método mostrou-se específico, linear (r = 0,9997, n = 3), preciso, exato e robusto, na faixa de 8,0 a 50,0 μg.mL-1, com tempo de corrida e o tempo de retenção de 5,0 e 3,5 minutos, respectivamente. M1 a M4 apresentaram morfologia esférica, com teor de fármaco entre 90 – 104%, e M5 a M8 exibiram morfologia achatada e distorcida, com teor de fármaco entre 67 – 75%. Nenhuma interação química foi observada nos espectros de infravermelho por transformada em Fourier para as micropartículas M1 a M4. No entanto, houve alargamento e aumento da intensidade de algumas bandas nos espectros das micropartículas M5 a M8, sugerindo uma modificação nas ligações químicas. As análises térmicas e de difração de raios X indicaram que a incorporação do EFV às micropartículas contribuiu para a amorfização do fármaco. Ensaios de liberação in vitro confirmaram a baixa solubilidade do fármaco em água (22,88%). As micropartículas liberaram menos de 22% em meio ácido, promovendo maior liberação em pH 6,8. Todas as formulações avaliadas aumentaram a solubilidade e a eficiência de dissolução do fármaco, e exibiram cinética de liberação biexponencial, segundo os modelos matemáticos aplicados, sendo estratégias interessantes para o aumento da biodisponibilidade do fármaco. A M3 foi responsável pela maior liberação em pH 6,8 (73,69%) e, de acordo com o modelo de Korsmeyer-Peppas, apresentou características de transporte anômalo (difusão e erosão do polímero), enquanto que nas demais micropartículas o processo de liberação foi controlado por difusão. No ensaio in vivo, os animais submetidos à administração de M3 apresentaram menos alterações nos parâmetros bioquímicos, quando comparados ao grupo de tratamento com EFV, sugerindo que as micropartículas contribuíram para a redução dos efeitos colaterais tais como aumento nos níveis plasmáticos de colesterol, LDL e HDL e triglicerídeos. Foi observado um decaimento na quantificação do fármaco puro durante o período avaliado no estudo de estabilidade. As micropartículas não mostraram mudanças significativas no teor de EFV durante 180 dias. Os termogramas indicaram que não houve diferença na faixa de fusão do fármaco e nos decaimentos das curvas termogravimétricas, sugerindo que não houve formação de novos produtos e, consequentemente, perda da estabilidade. A avaliação do índice de Carr e do fator de Hausner indicou que a M3 apresentou melhores propriedades de fluxo e de compactação quando comparadas ao EFV puro, características que podem melhorar o escoamento e facilitar a rotina industrial.

The 2004 Indian Ocean and 2011 Tohoku tsunami events have shown the destructive power of tsunami inundation to the constructed environment in addition to the tragic loss of life. A comparable event is expected for the Cascadia Subduction Zone (CSZ) which will impact the west coast of North America. Research efforts have focused on understanding and predicting the hazard to mitigate potential impacts. This thesis presents two manuscripts which pertain to estimating infrastructure damage and determining design loads of tsunami inundation. The first manuscript estimates damage to buildings and economic loss for Seaside, Oregon, for CSZ events ranging from 3 to 25 m of slip along the entire fault. The analysis provides a community scale estimate of the hazard with calculations performed at the parcel level. Hydrodynamic results are obtained from the numerical model MOST and damage estimates are based on fragility curves from the recent literature. Seaside is located on low lying coastal land which makes it particularly sensitive to the magnitude of the events. For the range of events modeled, the percentage of building within the inundation zone ranges from 9 to 88%, with average economic losses ranging from $2 million to $1.2 billion. The second manuscript introduces a new tsunami inundation model based on the concept of an energy grade line to estimate the hydrodynamic quantities of maximum flow depth, velocity, and momentum flux between the shoreline and extent of inundation along a 1D transect. Using the numerical model FUNWAVE empirical relations were derived to tune the model. For simple bi-linear beaches the average error for the tuned model in flow depth, velocity, and momentum flux were 10, 23, and 10%, respectively; and for complex bathymetry at Rockaway Beach, Oregon, without recalibration, the errors were 14, 44, and 14% for flow depth, velocity, and momentum flux, respectively. / Graduation date: 2013

Les gazoles, carburant automobile préféré des français, sont « additivés » afin de permettre leur utilisation en hiver. Les n-paraffines présentes dans ces gazoles cristallisent en effet à basse température. Ces cristaux peuvent alors entraîner le colmatage des filtres protecteurs situés en amont du moteur. Des polymères à base d'éthylène, notamment les copolymères éthylène-acétate de vinyle (EVA), sont utilisés pour abaisser la température à laquelle les problématiques de filtration adviennent. Un nouveau procédé de copolymérisation radicalaire d'éthylène et d'acétate de vinyle, à plus basse pression et à plus basse température, que le procédé industriel actuel, a été développé au cours de cette thèse. Une grande variété d'EVA a ainsi été obtenue. Ils présentent des caractéristiques structurelles et une efficacité, pour le traitement des gazoles, similaires aux EVA commerciaux. Ce procédé a, par ailleurs, permis la synthèse d'autres co- et terpolymères de l'éthylène variant par la nature des comonomères polaires utilisés ou par l'architecture. Des modèles de copolymères EVA ont été également synthétisés par métathèse. La grande diversité d'additifs polymères à disposition combinée à des techniques d'analyse thermique et de diffusion des rayons X mises en oeuvre au plus proche de l'application (en particulier dans le gazole), ont permis de mieux appréhender leur mode d'action sur la cristallisation des n-paraffines. Les spécificités structurelles, des polymères, conditionnant leur efficacité pour le traitement de la tenue à froid des gazoles ont également pu être établies / The additivation of diesel fuels allows operating engines at low temperatures without filter blocking and thus fulfilling legal requirements. Ethylene based copolymers such as ethylene-vinyl acetate copolymers, made by free radical polymerization at high pressure (above 2000 bars) and high temperature (above 200 °C) are frequently used as middle distillate cold flow improvers (MDFI). A new free radical copolymerization process of ethylene and vinyl acetate in organic solvent media has been developed. This process gives access to polymers close to commercial MDFI additives under tremendous less drastic conditions (under 250 bars of ethylene and 70 °C). Thanks to this process, a wide diversity (variation of the nature of the polar unit, of polymer architecture…) of ethylene based polymers was obtained. Moreover, EVA model copolymers have been synthesized by metathesis. Thanks to these numerous and diverse ethylene based polymers combined with thermal analysis and X-ray scattering studies a better understanding of the operating mode of these additives in a diesel fuel has been achieved. The structural characteristics of the polymers enabling their effectiveness as diesel fuel cold flow improvers have also been established