Thermal transitions and temperature dependent mechanical behavior of wheat straw/talc isotactic/impact modified polypropylene composites

Abstract

Dynamic mechanical thermal analysis was used to evaluate temperature-dependent mechanical performance of wheat straw/talc polypropylene composites intended for automotive components as well as thermal properties of the produced formulations. Dynamic mechanical thermal analysis results were also correlated with impact tests and static bending test results. Isotactic and impact-modified copolymer polypropylene composites with various amounts of wheat straw or talc were prepared using extrusion followed by injection molding. Different thermal transitions as well as mechanical performance of the composites were evaluated and the effects of fiber loading, matrix type, filler type and hybridization were studied. Results indicated different mechanical behaviors of the two fillers within and between the two matrices. Modulus retention term and relative storage modulus were used as parameters defining mechanical performance at various temperatures. It was found that wheat straw composites were generally comparable to talc composites with better performance at very low or very high temperature regions. The correlations between the dynamic mechanical loss factor values at room temperature and impact strength data revealed a good relationship only for the isotactic polypropylene composites whereas statistically significant correlations were established between flexural strength and impact data for all formulations.