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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Systèmes supramoléculaires biomimétiques : les complexes bols, synthèse, propriétés et réactivité / Biomimetic supramolecular systems : bowl complexes, synthesis, properties and reactivity

Parrot, Arnaud 16 December 2015 (has links)
Le ligand Rim3, constitué d’une cavité resorcinarène fonctionnalisée par 3 groupements méthylimidazole a été synthétisé et étudié. Ce ligand est capable de coordiner différents métaux de transitions comme le zinc et le cuivre. Ces complexes possèdent des propriétés hôte-invité intéressantes et une sélectivité avec la taille de la cavité. La complexation d’invités acides nécessite l’addition d’une base exogène. De plus, la présence de base peut être nécessaire pour réaliser des réactions d’hydratation ou d’hydrolyse. Dans ce manuscrit sont présentés différents ligands cavitaires resorcinarène avec 4 imidazoles greffés. Chaque ligand et complexe associé présente des solubilités différentes. Nous étudierons d’abord la synthèse et la caractérisation des systèmes en milieu organique ou aqueux. Les études de complexation montreront la forte affinité associée à ces complexes en milieu organique. L’étude des propriétés hôte-invité montre que le complexe est capable de coordiner un invité acide de manière quantitative dans les conditions RMN. Cette coordination ne nécessite pas l’addition de base. Le 4e imidazole joue le rôle de base intramoléculaire et n’est pas nécessaire à la coordination. Deux positions labiles en cis sont également disponibles, attesté par la coordination de ligands bidentes. Le complexe zincique [Rim4ZnII(EtOH)](ClO4)2 montre des propriétés d’hydratation des nitriles. Dans l’acétonitrile avec 35% d’eau à 70°C, le complexe forme de l’acétamide de manière catalytique. L’addition de base n’est pas nécessaire et le pH n’évolue pas avec la réaction. Dans l’eau avec 10% d’acétonitrile, [WRim(OH)44 Zn(H2O)](NO3)2 catalyse l’hydratation en acétamide mais est inhibé par l’hydrolyse successive en acétate. / In this manuscript, we present the synthesis and caracterisation of three tetradentate bowlshaped ligand. These ligands are resorcin[4]arene functionnalized by four methylimidazole. Each ligand is soluble in a different medium, such as organic solvent, water and mixed solvent. The four methylimidazoles are able to coordinate several metal ions, such as zinc, copper and iron. We then present the host-guest properties of the complexes. The complexes are able to coordinate acidic guests without addition of an exogenous base, thanks to the fourth imidazole. Two labiles positions are avalaible in cis, and bidentate ligands are able to coordinate the metal ions. Finally, we present the reactivity of the complexes. The zinc complex, [Rim4Zn]2+ catalyses the acetonitrile hydration with 35% water at 70°C. In an aqueous media with 10% water,[WRim(OH)44 Zn(H2O)](NO3)2 catalyses not only the acetonitrile hydration but also it’s subsequent hydrolysis into acetate.
72

SÍNTESE E CARACTERIZAÇÃO DE DÍADES VISANDO A APLICAÇÃO EM DISPOSITIVOS FOTOVOLTAICOS

Becher, Tiago Branco 12 April 2013 (has links)
Made available in DSpace on 2017-07-24T19:38:09Z (GMT). No. of bitstreams: 1 Tiago Branco Brecher.pdf: 1790856 bytes, checksum: f4d811ea50a13d94dfcb1d13c6444f12 (MD5) Previous issue date: 2013-04-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this paper we address the development of synthetic routes to four organic structures called dyads, which are compounds formed by an electron donating group covalently attached to an electron acceptor group. What sparked your interest in synthesizing these molecules was the potential of being applied in organic photovoltaic devices, because this type of structure has the ability of promoting a charge separation of the exciton generated after light absorption. This happens due to the proximity between the donor and acceptor species. In this work we have chosen the group derived from naphthalamide as electron donor, which has features like thermal and photochemical stabilities and conjugated double bonds, which cause the electrons p remain delocalized, facilitating the release of electrons when they receive energy. As electron acceptor it was chosen groups derived from fluorene,thiophene and benzonitrile containing both nitrile groups (strongly electron with drawing electron), which have characteristics of electron acceptors. The synthetic route of the NCT dyad was composed of two stages. In the first step of the synthesis of this dyad it was added a saturated chain of six carbon, proven by the NMR data with the appearance of the signs of the carbons of the chain in the region 1.5 to 3 ppm, so the next step was performed by the reaction of this product with the electron acceptor, the thiophene. In the synthetic route of the NCF it was performed three steps of the five motions initially, the first step being the same as performed for the preceding dyad. In the next step the objective of the reaction was the addition of iodine to fluorene derivative, which was confirmed by the appearance of bands of C-I bond in the IR spectra. The third and final stage of the dyad NCF had the goal of replacing the iodines by cyano group. The results show that this step it actually occurred mainly because of the nitrile band in the IR spectrum. The dyad NCB had only one step, in which the derivative naphthalamide was linked to the benzonitrile by a SN2 reaction, which was confirmed by NMR analysis that shows all the characteristic signs of the product formed. The dyad NT was the only one that did not have the separation between the donor and acceptor of electrons by a aliphatic carbon chain. Its synthesis aimed to connect the two reagents directly in only one step. All synthesized products were characterized by IR spectroscopy and 1H NMR, and the determination of their melting point, with these characterization it was concluded that only the dyad NCB was successfully obtained. / Neste trabalho abordamos o desenvolvimento de rotas sintéticas para quatro estruturas orgânicas chamadas díades, que são compostos formados por um grupo doador de elétrons conectado covalentemente a um grupor aceitador de elétrons. O que despertou o interesse em sintetizar estas moléculas foi o potencial de serem aplicadas em dispositivos fotovoltaicos orgânicos, pois esse tipo de estrutura tem como propriedade principal a capacidade de, após a absorção de luz, promover uma separação de carga do éxciton gerado devido à proximidade entre a espécie doadora e aceitadora de elétrons. Nesse trabalho foi escolhido o grupo derivado da naftalamida como doador de elétrons, que tem como características estabilidades térmica e fotoquímica e duplas ligações conjugadas, que fazem com que os elétrons p fiquem delocalizados, facilitando a liberação de elétrons quando estes recebem energia. Como aceitador de elétrons foram escolhidos grupos derivados do fluoreno,tiofeno e da benzonitrila ambos contendo grupos nitrilas (fortemente elétron-retirador de elétrons), os quais apresentam características aceptoras de elétrons. A rota sintética da díade NCT foi composta de duas etapas. Na primeira etapa de síntese desta díade foi adicionada uma cadeia saturada de seis carbonos, comprovada pelos dados de RMN com o surgimento dos sinais dos carbonos da cadeia na região de 1,5 a 3 ppm, para que na próxima etapa fosse realizada a reação deste produto com o aceitador de elétrons, o tiofeno. Na rota sintética da díade NCF foram realizadas três etapas das cinco propostas inicialmente, sendo a primeira etapa a mesma da realizada para a díade anterior. Na etapa seguinte o objetivo da reação foi à adição do iodo ao derivado fluoreno, a qual foi comprovada pelo surgimento das bandas da ligação C-I no espectro de IV. A terceira e última etapa da díade NCF teve o objetivo da substituir os iodos pelo grupo ciano. Os resultados desta etapa mostram que isto realmente ocorreu principalmente pelo surgimento da banda da nitrila no espectro de IV. A díade NCB teve somente uma etapa, na qual o derivado da naftalamida se uniu ao da benzonitrila por uma reação SN2, que foi confirmado pela analise de RMN que apresenta todos os sinais característicos do produto formado. A díade NT é a única que não possui a separação entre o doador e o aceitador de elétrons por uma cadeia de carbonos. Sua síntese teve como objetivo ligar os dois reagentes diretamente em somente uma etapa. Todos os produtos sintetizados foram caracterizados pelas espectroscopias de IV e de RMN de 1H,além da determinação de seu ponto de fusão, com estas análises foi concluído que somente a díade NCB foi sintentizada.
73

Catalytic Hydrogenation of Nitrile Rubber in High Concentration Solution

Li, Ting January 2011 (has links)
Chemical modification is an important way to improve the properties of existing polymers, and one of the important examples is the hydrogenation of nitrile butadiene rubber (NBR) in organic solvent by homogeneous catalysis in order to extend its application. This process has been industrialized for many years to provide high performance elastomers (HNBR) for the automotive industry, especially those used to produce components in engine compartments. In the current commercial process, a batch reactor is employed for the hydrogenation step, which is labor intensive and not suitable for large volume of production. Thus, novel hydrogenation devices such as a continuous process are being developed in our research group to overcome these drawbacks. In order to make the process more practical for industrial application, high concentration polymer solutions should be targeted for the continuous hydrogenation. However, many problems are encountered due to the viscosity of the high concentration polymer solution, which increases tremendously as the reaction goes on, resulting in severe mass transfer and heat transfer problems. So, hydrogenation kinetics in high concentration NBR solution, as well as the rheological properties of this viscous solution are very essential and fundamental for the design of novel hydrogenation processes and reactor scale up. In the present work, hydrogenation of NBR in high concentration solution was carried out in a batch reactor. A commercial rhodium catalyst, Wilkinson’s catalyst, was used with triphenylphosphine as the co-catalyst and chlorobenzene as the solvent. The reactor was modified and a PID controller was tuned to fit this strong exothermic reaction. It was observed that when NBR solution is in a high concentration the kinetic behavior was greatly affected by mass transfer processes, especially the gas-liquid mass transfer. Reactor internals were designed and various agitators were investigated to improve the mechanical mixing. Experimental results show that the turbine-anchor combined agitator could provide superior mixing for this viscous reaction system. The kinetic behavior of NBR hydrogenation under low catalyst concentration was also studied. It was observed that the hydrogenation degree of the polymer could not reach 95% if less than 0.1%wt catalyst (based on polymer mass) was used, deviating from the behavior under a normal catalyst concentration. The viscosity of the NBR-MCB solutions was measured in a rotational rheometer that has a cylinder sensor under both room conditions and reaction conditions. Parameters that might affect the viscosity of the solutions were studied, especially the hydrogenation degree of polymer. Rheological properties of NBR-MEK solutions, as well as NBR melts were also studied for relevant information. It is concluded that the hydrogenation kinetics deviates from that reported by Parent et al. [6] when polymer is in high concentration and/or catalyst is in low concentration; and that the reaction solution (HNBR/NBR-MCB solution) deviates from Newtonian behavior when polymer concentration and hydrogenation degree are high.
74

Catalytic Hydrogenation of Nitrile Rubber in High Concentration Solution

Li, Ting January 2011 (has links)
Chemical modification is an important way to improve the properties of existing polymers, and one of the important examples is the hydrogenation of nitrile butadiene rubber (NBR) in organic solvent by homogeneous catalysis in order to extend its application. This process has been industrialized for many years to provide high performance elastomers (HNBR) for the automotive industry, especially those used to produce components in engine compartments. In the current commercial process, a batch reactor is employed for the hydrogenation step, which is labor intensive and not suitable for large volume of production. Thus, novel hydrogenation devices such as a continuous process are being developed in our research group to overcome these drawbacks. In order to make the process more practical for industrial application, high concentration polymer solutions should be targeted for the continuous hydrogenation. However, many problems are encountered due to the viscosity of the high concentration polymer solution, which increases tremendously as the reaction goes on, resulting in severe mass transfer and heat transfer problems. So, hydrogenation kinetics in high concentration NBR solution, as well as the rheological properties of this viscous solution are very essential and fundamental for the design of novel hydrogenation processes and reactor scale up. In the present work, hydrogenation of NBR in high concentration solution was carried out in a batch reactor. A commercial rhodium catalyst, Wilkinson’s catalyst, was used with triphenylphosphine as the co-catalyst and chlorobenzene as the solvent. The reactor was modified and a PID controller was tuned to fit this strong exothermic reaction. It was observed that when NBR solution is in a high concentration the kinetic behavior was greatly affected by mass transfer processes, especially the gas-liquid mass transfer. Reactor internals were designed and various agitators were investigated to improve the mechanical mixing. Experimental results show that the turbine-anchor combined agitator could provide superior mixing for this viscous reaction system. The kinetic behavior of NBR hydrogenation under low catalyst concentration was also studied. It was observed that the hydrogenation degree of the polymer could not reach 95% if less than 0.1%wt catalyst (based on polymer mass) was used, deviating from the behavior under a normal catalyst concentration. The viscosity of the NBR-MCB solutions was measured in a rotational rheometer that has a cylinder sensor under both room conditions and reaction conditions. Parameters that might affect the viscosity of the solutions were studied, especially the hydrogenation degree of polymer. Rheological properties of NBR-MEK solutions, as well as NBR melts were also studied for relevant information. It is concluded that the hydrogenation kinetics deviates from that reported by Parent et al. [6] when polymer is in high concentration and/or catalyst is in low concentration; and that the reaction solution (HNBR/NBR-MCB solution) deviates from Newtonian behavior when polymer concentration and hydrogenation degree are high.
75

Avaliação das propriedades mecânicas e reológicas de composições de borracha nitrílica vulcanizadas com resina fenólica / Avaliação das propriedades mecânicas e reológicas de composições de borracha nitrílica vulcanizadas com resina fenólica / Evaluatin of mechanical and rheological properties of vulcanized nitrile rubber compositions with phenolic resin / Evaluatin of mechanical and rheological properties of vulcanized nitrile rubber compositions with phenolic resin

José Luiz Leite Sanchez 26 June 2008 (has links)
Neste trabalho de Dissertação de Tese, composições do copolímero de butadieno-acrilonitrila (NBR) foram vulcanizadas utilizando como agentes de vulcanização, a resina fenólica e o enxofre, com diferentes proporções de resina fenólica e uma única proporção de enxofre. O sistema ativador foi composto por policloropreno e óxido de zinco para as composições com resina fenólica, enquanto que por ácido esteárico e óxido de zinco para a composição com enxofre. Os materiais foram vulcanizados em uma temperatura de 190C. Foi avaliada a influência da variação dos componentes das composições sobre as propriedades reométricas, físico-mecânicas e reológicas dos materiais. Para auxiliar na interpretação dos resultados obtidos para as propriedades reométricas e físico-mecânicas, foi utilizado um planejamento estatístico de análise de variância para verificar a possibilidade da influência das variáveis e suas possíveis combinações nas propriedades avaliadas. Para as composições vulcanizadas com resina fenólica, os resultados mostraram que a composição de borracha nitrílica se tornou mais rígida com a presença da resina. Também foi observada a ocorrência de pós-cura nas composições vulcanizadas com resina fenólica. Os ensaios reológicos revelaram uma homogeneidade nas amostras submetidas aos testes de varredura de deformação, com desvio de linearidade a partir de 10% de deformação. / In this Thesis Dissertation, acrylonitrile-butadiene rubber (NBR) compositions were vulcanized using phenolic resin and sulfur as vulcanization agents with different proportions of phenolic resin and only one proportion of sulfur. The activator system was composed of polycloroprene and zinc oxide to phenolic resin compositions, while stearic acid and zinc oxide to sulfur composition. The materials were vulcanized in a temperature of 190C. The influence of the components content on rheometric, physico-mechanical and rheological properties of the materials was evaluated. In order to assist in the interpretation of the to physico-mechanical and rheometric properties results, a statistical planning of variant analysis was used to observe a possible influence of the variables and also their possible associations into the evaluated properties. The results showed that the nitrile rubber become more stiffness with the presence of phenolic resin. It was also observed the occurrence of post-vulcanization on the compositions vulcanized with phenolic resin. The rheological results showed homogeneity of the samples submitted to a strain sweep test, with a linear plateau until 10% of strain.
76

Modificação química do poli(cloreto de vinila) com nucleófilos nitrogenados assistida por micro-ondas / Chemical modification of poly(vinyl chloride) with nitrogen nucleophiles assisted by microwave irradiation

Mauro Vinícius Almeida da Silva 28 February 2013 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nesse trabalho foram realizadas reações de substituição nucleofílica (SN2), utilizando aquecimento térmico convencional e por irradiação de micro-ondas (MO), de alguns átomos cloro em amostras comerciais de poli(cloreto de vinila) (PVC), por grupos nitrila e também por grupos azida. Os grupos nitrila e azida foram substituidos na matriz em diferentes teores (10% e 20%). As reações do PVC com azida foram eficazes, apresentado percentuais de derivatização muito próximos dos valores desejados. Já no estudo com a nitrila não foi obtido o resultado esperado. Os copolímeros PVC azido substituídos foram modificados com propargilato de etila, sob catálise de iodeto de cuproso (CuI), para a obtenção de heterocíclicos do tipo triazólicos. Todos os copolímeros obtidos foram caracterizados por espectroscopia na região do infravermelho (FTIR) e os teores de nitrogênio incorporado foram determinados por análise elementar (AE). Através da análise dos dados obtidos, foi comprovado que a utilização da irradiação micro-ondas, quando comparada ao aquecimento convencional, é um processo mais seletivo e diminui, significativamente, os tempos de reação / In this work we had performed nucleophilic substitution reactions (Sn2) of some chlorine atoms in commercial samples of poly (vinyl chloride) (PVC), nitrile groups and also by azide groups, using both conventional thermal heating and microwave irradiation (MW).Nitrile and azide groups were replaced in the matrix at diverse levels (10% and 20%). The reactions of PVC with azide were effective, reaching a percentage derivatization very near to the desired values. In the study with the nitrile although we have not obtained the expected results. The substituted azido copolymers were modified with propargilato acetate, under catalysis of copper iodide (CuI) to obtain triazole heterocyclic type. All copolymers were labeled by infrared spectroscopy (FTIR) and nitrogen contents were determined by corporate elemental analysis (EA). Through analysis of the data obtained, it was verified that the use of microwave irradiation in comparison to conventional heating is a more selective process and reduces significantly reaction times
77

Comportamento tribológico dos compósitos poliméricos utilizados no anel de atrito do amortecedor torcional de discos de embreagem / Tribological behavior of polymeric composites used ring of friction in the torcional damper of clutch disc.

Rosa, Avital Gabriel de Almeida 18 November 2017 (has links)
Submitted by Avital Rosa (avitalgabriel@hotmail.com) on 2018-01-23T16:54:36Z No. of bitstreams: 2 Dissertação de Mestrado_PPGCM _Aluno Avital Gabriel de Almeida Rosa.pdf: 5418816 bytes, checksum: f6f7f278fa5c0f54a96a91c4b6a87ad0 (MD5) Carta comprovante da versão final - Avital.png: 3621222 bytes, checksum: 7228740ac2bf0d70ebaad75deb22b89d (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2018-01-23T17:13:20Z (GMT) No. of bitstreams: 2 Dissertação de Mestrado_PPGCM _Aluno Avital Gabriel de Almeida Rosa.pdf: 5418816 bytes, checksum: f6f7f278fa5c0f54a96a91c4b6a87ad0 (MD5) Carta comprovante da versão final - Avital.png: 3621222 bytes, checksum: 7228740ac2bf0d70ebaad75deb22b89d (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2018-01-23T17:13:31Z (GMT) No. of bitstreams: 2 Dissertação de Mestrado_PPGCM _Aluno Avital Gabriel de Almeida Rosa.pdf: 5418816 bytes, checksum: f6f7f278fa5c0f54a96a91c4b6a87ad0 (MD5) Carta comprovante da versão final - Avital.png: 3621222 bytes, checksum: 7228740ac2bf0d70ebaad75deb22b89d (MD5) / Made available in DSpace on 2018-01-23T17:13:44Z (GMT). No. of bitstreams: 2 Dissertação de Mestrado_PPGCM _Aluno Avital Gabriel de Almeida Rosa.pdf: 5418816 bytes, checksum: f6f7f278fa5c0f54a96a91c4b6a87ad0 (MD5) Carta comprovante da versão final - Avital.png: 3621222 bytes, checksum: 7228740ac2bf0d70ebaad75deb22b89d (MD5) Previous issue date: 2017-11-18 / Não recebi financiamento / The three cylinder motors tend to vibrate more than the conventional four cylinder ones. In this new condition the transmission system and in particular the torsional damper of the clutch disc is subjected to sever wear and friction. The great challenge is to select new materials with low wear rate and adequate friction coefficient to attenuate this new vibration level. In this work three different candidate materials to be used as friction rings inside the torsional damper of clutch discs were tested in terms of wear resistance and friction. Two of the studied materials are currently used in the market (PA66 35 GF and NBR) in four cylinder motors and the third is currently used in clutch facing (NBR matrix composite). The materials were purchased from Schaeffler suppliers. The first step was the microstructural characterization and determination of the thermal stability of the three materials without the influence of friction. For that, the microstructure was analyzed by optical and electronic microscopy of Scanning (SEM), the amount of fibers and inorganic reinforcers was determined by burning tests and,the transition temperatures were determined by differential calorimetry. Two aging temperatures were studied 80 and 150oC. The effect of the ageing time was determined by hardness and infrared spectroscopy measurements. Among the three materials and clutch facing, they show a more stable structure in the temperature range between 80 and 150ºC. The PA66GF35 suffered changes in crystalline content and the NBR thermal degradation. The second step consisted in determining the wear characteristics of the material in bench tests with the objective of measuring the wear rate and friction coefficient of the material under extreme conditions of specific pressure and velocity (DIN50320, 1979). The results of the friction test had the following classification: NBR (0.13)> PA66GF35 (0.11)> clutch facing (0.09). Despite having a lower coefficient of friction, the clutch facing was the only material that achieved the minimum wear resistance required for the friction ring. Therefore the clutch facing is the best material for a 3 cylinder engine that requires a higher wear and thermal resistance on the clutch plate. / O motor de três cilindros tende a ter vibrações maiores que do motor de quatro cilindros. Nesta nova configuração o sistema de transmissão e, em particular, o amortecedor torcional do disco de embreagem fica sujeito a condições de desgaste e atrito mais severas. O grande desafio atual está na busca de componentes com baixo desgaste e um coeficiente de atrito adequado e que elimine os ruídos. Neste trabalho foram caracterizados os materiais utilizados na fabricação de anéis de atrito do amortecedor torcional de discos de embreagem quanto à resistência ao desgaste e atrito. Dois dos três materiais são hoje utilizados no mercado como componente de anel de atrito (PA66GF35 e elastômero NBR) em motores de quatro cilindros e o terceiro é atualmente utilizado em Lonas de embreagem. A primeira etapa consistiu na caracterização microestrutural e determinação da estabilidade térmica dos três materiais sem a influência de atrito. Para isso foram realizadas análises em microscopia óptica e eletrônica de varredura (MEV), teste de queima para porcentagem de fibra e tratamentos de envelhecimento, seguido de análises através de calorimetria diferencial, dureza, espectroscopia no infravermelho. Dentre os três materiais a lona de embreagem mostrou ser a mais estável na faixa de temperaturas entre 80 e 150ºC. O PA66GF35 sofreu alteração de cristalinidade e o NBR endurecimento devido à degradação térmica. A segunda consistiu na determinação das características de desgaste do material em função das variáveis de influência em condições controladas de laboratório. Para isso foi realizado um teste de bancada com o objetivo de medir a taxa de desgaste e coeficiente de atrito do material em condições extremas de pressão específica e velocidade (DIN50320, 1979). Os resultados do ensaio o atrito teve a seguinte classificação: NBR (0,13) >PA66GF35 (0,11)>Lona (0,09). Apesar de ter um coeficiente de atrito menor, a Lona de embreagem foi o único material que atingiu a resistência ao desgaste mínima exigida para o anel de atrito. Portanto a Lona de embreagem é o melhor material para um motor 3 cilindros que exige uma maior resistência ao desgaste e térmica, no disco de embreagem.
78

Avaliação das propriedades mecânicas e reológicas de composições de borracha nitrílica vulcanizadas com resina fenólica / Avaliação das propriedades mecânicas e reológicas de composições de borracha nitrílica vulcanizadas com resina fenólica / Evaluatin of mechanical and rheological properties of vulcanized nitrile rubber compositions with phenolic resin / Evaluatin of mechanical and rheological properties of vulcanized nitrile rubber compositions with phenolic resin

José Luiz Leite Sanchez 26 June 2008 (has links)
Neste trabalho de Dissertação de Tese, composições do copolímero de butadieno-acrilonitrila (NBR) foram vulcanizadas utilizando como agentes de vulcanização, a resina fenólica e o enxofre, com diferentes proporções de resina fenólica e uma única proporção de enxofre. O sistema ativador foi composto por policloropreno e óxido de zinco para as composições com resina fenólica, enquanto que por ácido esteárico e óxido de zinco para a composição com enxofre. Os materiais foram vulcanizados em uma temperatura de 190C. Foi avaliada a influência da variação dos componentes das composições sobre as propriedades reométricas, físico-mecânicas e reológicas dos materiais. Para auxiliar na interpretação dos resultados obtidos para as propriedades reométricas e físico-mecânicas, foi utilizado um planejamento estatístico de análise de variância para verificar a possibilidade da influência das variáveis e suas possíveis combinações nas propriedades avaliadas. Para as composições vulcanizadas com resina fenólica, os resultados mostraram que a composição de borracha nitrílica se tornou mais rígida com a presença da resina. Também foi observada a ocorrência de pós-cura nas composições vulcanizadas com resina fenólica. Os ensaios reológicos revelaram uma homogeneidade nas amostras submetidas aos testes de varredura de deformação, com desvio de linearidade a partir de 10% de deformação. / In this Thesis Dissertation, acrylonitrile-butadiene rubber (NBR) compositions were vulcanized using phenolic resin and sulfur as vulcanization agents with different proportions of phenolic resin and only one proportion of sulfur. The activator system was composed of polycloroprene and zinc oxide to phenolic resin compositions, while stearic acid and zinc oxide to sulfur composition. The materials were vulcanized in a temperature of 190C. The influence of the components content on rheometric, physico-mechanical and rheological properties of the materials was evaluated. In order to assist in the interpretation of the to physico-mechanical and rheometric properties results, a statistical planning of variant analysis was used to observe a possible influence of the variables and also their possible associations into the evaluated properties. The results showed that the nitrile rubber become more stiffness with the presence of phenolic resin. It was also observed the occurrence of post-vulcanization on the compositions vulcanized with phenolic resin. The rheological results showed homogeneity of the samples submitted to a strain sweep test, with a linear plateau until 10% of strain.
79

Modificação química do poli(cloreto de vinila) com nucleófilos nitrogenados assistida por micro-ondas / Chemical modification of poly(vinyl chloride) with nitrogen nucleophiles assisted by microwave irradiation

Mauro Vinícius Almeida da Silva 28 February 2013 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nesse trabalho foram realizadas reações de substituição nucleofílica (SN2), utilizando aquecimento térmico convencional e por irradiação de micro-ondas (MO), de alguns átomos cloro em amostras comerciais de poli(cloreto de vinila) (PVC), por grupos nitrila e também por grupos azida. Os grupos nitrila e azida foram substituidos na matriz em diferentes teores (10% e 20%). As reações do PVC com azida foram eficazes, apresentado percentuais de derivatização muito próximos dos valores desejados. Já no estudo com a nitrila não foi obtido o resultado esperado. Os copolímeros PVC azido substituídos foram modificados com propargilato de etila, sob catálise de iodeto de cuproso (CuI), para a obtenção de heterocíclicos do tipo triazólicos. Todos os copolímeros obtidos foram caracterizados por espectroscopia na região do infravermelho (FTIR) e os teores de nitrogênio incorporado foram determinados por análise elementar (AE). Através da análise dos dados obtidos, foi comprovado que a utilização da irradiação micro-ondas, quando comparada ao aquecimento convencional, é um processo mais seletivo e diminui, significativamente, os tempos de reação / In this work we had performed nucleophilic substitution reactions (Sn2) of some chlorine atoms in commercial samples of poly (vinyl chloride) (PVC), nitrile groups and also by azide groups, using both conventional thermal heating and microwave irradiation (MW).Nitrile and azide groups were replaced in the matrix at diverse levels (10% and 20%). The reactions of PVC with azide were effective, reaching a percentage derivatization very near to the desired values. In the study with the nitrile although we have not obtained the expected results. The substituted azido copolymers were modified with propargilato acetate, under catalysis of copper iodide (CuI) to obtain triazole heterocyclic type. All copolymers were labeled by infrared spectroscopy (FTIR) and nitrogen contents were determined by corporate elemental analysis (EA). Through analysis of the data obtained, it was verified that the use of microwave irradiation in comparison to conventional heating is a more selective process and reduces significantly reaction times
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Palladium(II)-Catalyzed Addition Reactions : Synthesis of Aryl Amidines and Aryl Ketones

Rydfjord, Jonas January 2017 (has links)
Palladium-catalyzed reactions have become one of the most important tools in modern organic chemistry due to its ability to catalyze the formation of new carbon-carbon bonds. The aim of the work presented in this thesis was to develop new palladium(II)-catalyzed addition reactions. In this work, cyanamides were investigated as a new substrate to give aryl amidines as products. The first protocol developed employed aryltrifluoroborates as the aryl partner, and the insertion of the aryl group into un-, mono-, and di-substituted cyanamides was successful for a wide variety of aryltrifluoroborates. An alternative method of generating the necessary intermediate for insertion into the cyanamide is the decarboxylative formation of aryl-palladium from aryl carboxylic acids. A protocol was developed for this reaction, but was unfortunately limited to a small number of ortho-substituted electron-rich aryl carboxylic acids. The mechanism was investigated by the means of DFT calculations and ESI-MS studies, and the rate-determining step was suggested to be the 1,2-carbopalladation based upon those results. A translation of the batch protocol to continuous-flow conditions was also demonstrated. The ideal method of generating the aryl-palladium species is by C-H bond activation, and this approach was demonstrated with indoles, giving a variety of 3-amidinoindoles as products. The mechanism was investigated by DFT calculations and a plausible catalytic cycle was proposed. A continuous-flow application of a desulfitative palladium(II)-catalyzed addition to nitriles to give ketones was developed. In addition, different reactor materials were evaluated in the microwave heated reactor cavity. Thus the reaction was shown to proceed with microwave heating in a borosilicate glass and an aluminum oxide reactor, and also in conditions mimicking conventional heating in a silicon carbide reactor. Finally, a protocol was developed for the convenient synthesis of sodium aryl sulfinates from Grignard and lithium reagents using a solid sulfur dioxide source as a safe alternative to the gas. The products of this protocol can be used as aryl-palladium precursors by a desulfitative process.

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