Electrically Conducting Polypropylene/Polyaniline-grafted-Short Glass Fiber Composites: Microstructure and Dynamic Mechanical Analysis

The thermal properties of isotactic polypropylene (iPP) reinforced with polyaniline-grafted-short glass fibers (PAn-g-SGF) at 10, 20, and 30 wt% concentration and iPP blended with 5 wt% PP-grafted-maleic anhydride (PP-gMA) and 30 wt% of PAn-g-SGF were investigated. iPP crystallizes into a spherulitic morphology, the microfiller promoted larger spherulite size and higher dynamic modulus, but the overall degree of crystallinity decreased as the concentration of PAn-g-SGF increased. The melting temperature, T-m, was not influenced by the microfiller. However, the crystallization temperature, T-c, as determined by DMA, first decreased reaching a minimum at ca. 20 wt%, and then increased, in contrast with Tc determined by DSC, it increased as concentration increased. The initial reduction in Tc observed by DMA seems to be associated with the crystallites growing from the microfiller into the matrix, the overall molecular dynamics then being less affected. On the other hand, increase in Tc above 20 wt% concentration suggests that the percolation threshold could be responsible for these results. Addition of the maleic anhydride copolymer produced higher shear modulus, transition temperatures, and activation energy, suggesting higher interaction between microfiller and polymer matrix. POLYM. ENG. SCI., 51:254-263,2011. (C) 2010 Society of Plastics Engineers