Elisângela Corradini

Composição química, propriedades mecânicas e térmicas da fibra de frutos de cultivares de coco verde

O consumo da agua de coco verde, in natura ou industrializada, vem gerando um grande problema ambiental, devido ao destino final da casca dos frutos. Aproximadamente 85% do peso bruto do coco verde e constituido pelas cascas, que sao acumuladas em lixoes ou as margens de estradas. Como a minimizacao da geracao desse residuo implicaria a reducao da atividade produtiva associada, o seu aproveitamento torna-se uma necessidade. Neste sentido, este estudo teve como objetivo investigar as caracteristicas da fibra de coco verde de diversos cultivares em funcao do ponto de colheita dos frutos, na composicao quimica, nas propriedades mecânicas e termicas, como forma de contribuir para avaliar seu potencial de aplicacao na elaboracao de novos materiais. Os resultados mostraram que a variacao da composicao quimica em funcao da cultivar de coco verde foi na faixa de 37,2 ± 0,8% a 43,9±0,7% e de 31,5±0,1% a 37,4±0,5% para os teores de lignina e celulose, respectivamente. A composicao quimica nao variou significativamente em funcao do ponto de maturacao para a fibra da cultivar Anao-Verde-de-Jiqui (AVeJ). A fibra de cultivares de coco verde e AVeJ em diferentes pontos de maturacao apresentaram propriedades termicas e mecânicas semelhantes, as quais sao proximas das propriedades das fibras de coco maduro, demonstrando, portanto, um potencial equivalente para serem utilizadas como reforco em matrizes polimericas.

Estudo das propriedades de compósitos biodegradáveis de amido/glúten de milho/glicerol reforçados com fibras de sisal

Biocomposites using starch/gluten/glycerol as matrix and sisal fibers were produced by melt-mixing in an intensive batch mixer connected to a torque rheometer at 130 °C. The samples were compression molded and than characterized by water absorption and mechanical test. In tensile test, the increasing in the Youngs modulus and ultimate tensile strenght were respectively of aproximately 560 and 162% in relation to matrix, whereas elongation at break decreased. The storage modulus increased with increasing fiber content whereas tan d curves decreased, confirming the reinforcing effect of the fibers. The addition of sisal fibers in matrix decreased the water absorption at equilibrium. The diffusion coefficient decreased sharply with 5% addition of fiber and further sisal fiber additions provoked only small variation. Optical microscopy observations revealed good dispersion of the sisal fibers into the matrix.

Microstructure and thermal and functional properties of biodegradable films produced using zein

Research is being conducted in an attempt to produce biodegradable packaging to replace plastic products, thereby reducing solid waste disposal. In this work, zein films were produced from vegetable oils (macadamia, olive and buriti) and from pure oleic acid. The surface of zein-based films made using oleic acid has a good lipid distribution. The high content of oleic acid produced a film with the greatest elongation at break (8.08 ± 2.71%) due to the greater homogeneity of the protein matrix. The different oils did not affect the glass transition temperature (Tg). Tg curves of films with fatty acids showed a reduction in mass at between 50 and 120 °C due to water evaporation. At 120 °C the weight loss was 3-5% and above this temperature further weight loss was observed with the highest loss being seen in the film made using pure oleic acid. In conclusion, although biodegradable films were produced using the four different oils, the film made from pure oleic acid has the best characteristics.