Thermal behavior of biocomposites

LILIANA B. MANFREDI; EXEQUIEL S. RODRIGUEZ; ANALÍA VÁZQUEZ

Buenos Aires, Argentina

Conferencia; 3st CONFERENCE ON SCIENCE AND TECHNOLOGY OF COMPOSITE MATERIALS, Comat 2005; 2005

Universidad Nacional de Mar del Plata - Universidad de Perugia

Thermal degradation of different natural fibre composites was studied. Unsaturated polyester (UP) and modified acrylic resins (Modar) were used as matrixes. The degradation was studied by means of thermogravimetric analysis. Residual mass percentage (TGA) and the derivative of the residual mass percentage (DTG) were determined. The resistance to thermal degradation by mass loss is a very important parameter for determining the maximum processing temperatures. Several natural fibers (jute, sisal and flax) and two resins were used to evaluate the effect of the composite components in thermal resistance of the final material. Glass fibre composites were included in this work for comparison proposes. Natural fibers started to degrade at about 210ºC. The whole degradation process involved two main steps. The first one is the thermal depolimerization of the hemicellulose and the cellulose and the second one is related to the decomposition of the a-cellulose. The decomposition of the lignin took place in a broad range of temperature, between 200 and 500ºC. Jute and sisal fibers showed a similar behaviour, with a starting point near 215ºC and a maximum degradation rate at 340ºC. Flax fibres started to degrade at higher temperatures, with the main peak at 345ºC. The better thermal stability (considering the thermal stability as the temperature needed to start the degradation process) of the flax fibres was attributed to their lower lignin content. Comparing the two matrices, it was observed that thermal resistance is higher for the Modar resin than for the unsaturated polyester, probably due to the action of the acrylic acid in the first one. The resulting composites thermal stability was in line with the results obtained for the components (fibers and matrices). Flax–Modar composites showed the higher degradation temperature. All the natural fiber composites showed worse thermal stability than glass fibers fiber composites.