Navegando por Palavras-chave "Elastômero"
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- ItemAcesso aberto (Open Access)Efeito da adição de líquidos iônicos em um copolímero elastomérico para preparação de eletrólitos sólidos para baterias de íon lítio(Universidade Federal de São Paulo, 2016-06-10) Silva Filho, Sinval Braz da [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The search for solid electrolytes for electrochemical devices (batteries, full cells) is object of intense research due to their benefits in comparison with the liquids, mainly due to the processability aspects, handling and leak elimination. Although studies involving solid polymeric electrolytes have 0been reported, the research for materials that combine good mechanical strength, elasticity, chemical and thermal stabilities and ionic conductivity is still emerging. In this context, the first part of this dissertation focuses on the preparation and characterization of solid polymeric electrolytes constituted by a commercial elastomer known as PEBAX-2533, containing 80% of polyether blocks (PE) and 20% of polyamide blocks (PA), modified with three different ionic liquids (EMImTf2N, EMImFAP, EMImTCB). In the next step, a lithium salt, LiTf2N, was added to PEBAX-2533 films containing 10% of the cited ionic liquids in order to produce solid polymer electrolytes for lithium ion batteries. PEBAX-2533 films containing more than 25% of the ionic liquids exhibited droplets on the surface of the film, indicating phase segregation. This was not observed for films containing 10% of the salt and therefore only these electrolytes were used in the further studies. The results showed that using this percentage, the ions of the ionic liquids are accommodated in the voids present in the amorphous regions of the elastomer. These films showed ionic conductivity around 10-6 Scm-1 at 25 ° C. When the lithium salt, LiTf2N, was added to these electrolytes of PEBAX-2533 and ionic liquids, the conductivity decreased due to the formation of aggregates of lithium cation and the anions of the ionic liquids, which have a low mobility, and therefore do not contribute for ionic conductivity. In addition, it was verified that the lithium clusters and ?free? Li+ also occupy the empty spaces on the elastomer and free Li+ establishes permanent ion-dipole interactions with the PE blocks. The electrolyte comprised of PEBAX-2533, ionic liquids and LiTf2N showed thermal stability up to 200 °C. With the addition of poly (ethylene oxide) (PEO) to PEBAX-2533 films containing 10% of EMImTf2N and LiTf2N at 40 °C, it was obtained an electrolyte with conductivity of 9.2 x 10-5 Scm-1.
- ItemAcesso aberto (Open Access)Estudo do efeito microbicida da adição de nanopartículas de prata em membranas de um copolímero de poliéter e poliamida comercial (PEBAX-2533)(Universidade Federal de São Paulo, 2024-06-05) Barros, Larissa Cardoso de [UNIFESP]; Camilo, Fernanda Ferraz [UNIFESP]; Silva, Flavia Tavares da; https://bv.fapesp.br/pt/pesquisador/93340/fernanda-ferraz-camilo/; http://lattes.cnpq.br/7155923130289771Este trabalho de conclusão de curso teve como objetivo principal a preparação de membranas elastoméricas utilizando o copolímero PEBAX-2533, enriquecido com nanopartículas de prata, com potencial uso em dispositivos médicos, como cateteres e implantes. O PEBAX-2533 é conhecido por suas excelentes propriedades mecânicas e flexibilidade. Nanopartículas de prata, escolhidas por suas eficazes propriedades microbicidas, foram sintetizadas utilizando o método bottom-up, que permite controle preciso sobre o tamanho e a forma das partículas. A síntese foi realizada em 1-butanol, um solvente capaz de dissolver eficientemente tanto o PEBAX-2533 quanto as nanopartículas de prata, garantindo a compatibilidade entre os componentes e a integridade das nanopartículas incorporadas. As membranas resultantes foram caracterizadas para avaliar a distribuição, estabilidade térmica e a integração das nanopartículas de prata na matriz do PEBAX. Os resultados mostraram que as membranas mantêm estabilidade térmica até 210 °C, o que as qualifica para aplicações biomédicas que exigem esterilização a altas temperaturas. Os testes funcionais focaram na capacidade das membranas de dispersar biofilmes de Pseudomonas aeruginosa, uma bactéria notória por sua resistência a tratamentos e prevalência em infecções hospitalares. Os resultados indicaram que as membranas contendo nanopartículas de prata são capazes de conter a formação de biofilmes. Em particular, a membrana com 1% de massa de nanopartículas de prata e 10 mM de concentração mostrou os melhores resultados, dispersando efetivamente o biofilme e impedindo a proliferação bacteriana.
- ItemAcesso aberto (Open Access)Preparação e caracterização de híbridos elastomericos a partir da organofilização da montmorilonita com líquido iônico(Universidade Federal de São Paulo, 2013-09-18) Fontana, Juliana Pedro [UNIFESP]; Faez, Roselena [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)This work aims to obtain an elastomeric hybrid based on nitrile rubber NBR and sodic clays that have been subjected to processes organophilization. Initially, thermal, structural and morphological properties when montmorillonite clay modified with quaternary ammonium salt (OMMT-n) and also when combining the salt with the ionic liquid bistrifluorometanossulfonilimideto 1-methyl-3-octilimidazólio were evaluated. Both processes organophilization clay, either with the use of quaternary ammonium salt or ionic liquid, were effective as regards increasing the basal spacing and thermal properties. In the second stage of labor, the organoclays were incorporated into the elastomeric matrix of nitrile rubber for two separate assessments: the effect of LI content employed in organophilization, from the addition of 5 phr loading in the matrix and the effect of clay content used in the blend. Processing and structural, rheological, mechanical, thermal and morphological properties were evaluated. Hybrids were prepared by mechanical mixing, using the mixing chamber of a Haake. The results show that efficient coorganofilização clay LI influenced with the processing steps of the hybrid, particularly in the addition of the vulcanizing system. The use of ionic liquid as a partial replacement of the quaternary ammonium salt influenced the thermal, mechanical, rheological and morphological properties of the nanocomposites prepared. Among these properties, the presence of IL leads to an increase of the thermal stability of hybrids, the better the reinforcing effect of the load on the matrix, improved load-matrix interactions with increasing Li content.