Resumo: Células a combustível usando membranas poliméricas condutoras de íons representam uma alternativa interessante para substituição de matrizes energéticas convencionais baseadas em combustíveis fósseis e para a geração de energia com mínimo impacto ambiental. Entretanto, as membranas poliméricas atualmente disponíveis apresentam certas propriedades intrínsecas que diminuem a eficiência e a durabilidade sob uso das células construídas, sendo as principais desvantagens o limite de temperatura de uso (devido a necessidade de presença de água para a condução iônica) e suscetibilidade a degradação mecânica, térmica e química. O presente trabalho tem como objetivo a obtenção, caracterização e avaliação do desempenho de membranas poliméricas híbridas baseadas em poli(éter imida) (PEI), um polímero com excelente resistência mecânica e química, e cuja condutividade protônica independe da presença de água, possibilitando o uso a temperaturas mais elevadas. As membranas poliméricas baseadas em poli(éter imida) foram modificadas quimicamente visando o aumento em seu caráter de condutor iônico. A incorporação de um argilomineral com escala nanométrica visou um aumento na resistência mecânica e térmica das membranas obtidas, condições fundamentais para a durabilidade sob uso de células a combustível, além de aumento de propriedades de barreira em relação aos gases de processo. As membranas foram avaliadas por FTIR, DSC, TGA, DMA, densidade, inchamento em água, transmissão de vapor de água e resistência à migração iônica. Os resultados obtidos são promissores, visto que foi possível alterar a propriedade condutora da membrana, sem perdas excessivas na resistência térmica e mecânica. Palavras-chave: Membrana polimérica, nanocompósito polimérico, célula a combustível, eletrólito polimérico. Hybrids Membranes with Potential Use in Fuel Cells -Part 1: Sulphonated Poly (etherimide) NanocompositesAbstract: Fuel Cells based in polymeric membranes are an alternative for the conventional energetic matrices based on fossil fuel and generation of energy with minimum environmental impact. However, polymeric membranes available nowadays for this specific use have some disadvantages, like low efficiency and cell durability. The aim of this work was to prepare and to characterize hybrid polymeric membranes for application as hydrogen fuel cell electrolytes. Membranes based in poly(ether imide) were chemically modified with sulfur groups to increase their ionic conductivity. The incorporation of mineral clay in nanometric scale aims to increase their mechanical and thermal properties. The membranes were evaluated by FTIR, DSC, TGA, DMA, density, hot water uptake, water vapor transmission and ionic migration resistance. The results leaded to a better structure versus properties balance, aiming the high performance of the obtained membranes. Keywords: Polymeric membrane, nanocomposite, fuel cell, polymeric electrolyte. IntroduçãoNos últimos anos, o desenvolvimento de células a combustível tem atraído enorme atenção por parte não somente d...
Resumo: Membranas poliméricas condutoras de íons têm sido cada vez mais estudadas para o uso em células a combustível. Entretanto, as membranas poliméricas disponíveis no mercado para este fim apresentam algumas limitações de condições de trabalho. Neste estudo o poli(carbonato) modificado quimicamente para uso como membrana condutora de íons foi caracterizado e teve seu desempenho avaliado. A formação de um nanocompósito baseado em sepiolita visou ao aumento na resistência mecânica e térmica das membranas, propriedades, a princípio, prejudicadas pela sulfonação do material. As membranas foram avaliadas por FTIR, DSC, TGA, DMA, inchamento em água, transmissão de vapor de água e resistência à migração iônica. Os resultados mostraram ser possível atingir um balanço estrutura versus propriedades visando a um elevado desempenho das membranas. Palavras-chave: Membrana polimérica, nanocompósito polimérico, célula a combustível, eletrólito polimérico. Hybrid Membranes of Polymer/Clay for Fuel Cell Applications. Part 2. Sulphonated Poly(Carbonate) NanocompositesAbstract: Ion-conducting polymeric membranes have been studied for use in fuel cells. However, polymeric membranes available in the market show some disadvantages. Here we modified polycarbonate chemically for use as ion-conducting membranes, and investigated its performance. The use of the nanoclay sepiolite aimed at improving the mechanical and thermal resistance, which are negatively affected by polymer sulphonation. The membranes were evaluated using FTIR, DSC, TGA, DMA, water swelling, water vapor uptake and ionic migration resistance. The results indicated it to be possible to reach a tradeoff between structure and properties for obtaining high-performance membranes.
Blends of polyamide 6 and nitrile rubber (PA6/NBR) dynamically vulcanized may generate innovative products for special purposes where both high temperature and chemical resistance are key factors. In this investigation, we show that the crystalline nature of the PA6 can be controlled in terms of its morphological aspects (degree of crystallinity, crystal size, and structure) as a consequence of the presence of NBR and processing additives. Our results indicate that this crystalline control is dependent on the plasticization caused by the processing additives. Furthermore, imide‐like linkage formation was favored in the presence of ethylene‐co‐vinyl acetate (EVA)‐g‐maleic anhydride, resulting in changes in the molecular mobility of the PA6 matrix, crystallization parameters, and viscoelastic properties when compared to the others EVA additives. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45576.
Fuel Cells based in polymers are an alternative for the conventional energetic matrices. However, materials currently available still present disadvantages to overcome. Membranes of polycarbonate (PC)/sulfonated polycarbonate (PCs) blend/sepiolite nanocomposites have previously been studied by the authors, resulting in good mechanical properties and promising properties of vapor transmission and ionic migration resistance. However, their production in large scale is still a challenge. The aim of this work was the development further the formulation and processing of the previously studied material. Films of PC/PCs blends (50/50 wt%) with different content of sepiolite clay, with and without chemical modification, have been prepared in an extruder and evaluated by FTIR, XRD, DSC, TGA, DMA, tension strength and water vapor transmission (WVT). Even after two processing steps, the blend-based nanocomposites keep good thermal and mechanical properties. However, changes in WVT were observed with respect to data obtained in previous studies.
Polyamide 6 (PA6)/NBR blends are interesting because of their supposed properties at elevated temperatures. The blend, however, has a critical problem in terms of processing stability, as a result of the thermal degradation of the NBR phase. We evaluate a system of dissimilar addition of antioxidant in each phase (a combination of Irganox®/Irgafos® for the PA phase, and Naugard 445® for the NBR phase) and study the influence of these antioxidants on the properties of the blend. The evaluation was performed through tensile strength, differential scanning calorimetry (DSC), thermogravimetric analysis, and X-ray diffraction analysis. The influence of the antioxidant system on the crystallization process of the PA phase was evaluated through isothermal DSC analysis. Results showed the best combination of antioxidant addition in master batches and during processing.
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