Improved performance of isotactic polypropylene/titanium dioxide composites: Effect of processing conditions and filler content

Titanium dioxide (TiO2) filled isotactic polypropylene (iPP) with various content of TiO2, which was used as filler, were first single-extruded by an extruder, and then double-molded by compression molding. Scanning electron micrographs show a better adhesion between iPP and filler in the extrusion cum compression-molded samples than the extrusion-molded ones. X-ray diffraction and IR spectral studies reveal a structural change from a three-phase (alpha, beta, and gamma) crystalline system of the neat iPP sample to only alpha-form due to inclusion of fillers. Microhardness increases rapidly and then levels off with increasing filler content and also shows variations with respect to molding conditions. A slight decrease of melting temperatures and a considerable increase of degradation temperatures of the samples with addition of filler are also observed. The dc electrical resistivity is observed to decrease with increasing TiO2 content and temperature. Both the thermal and electrical properties are also found to affect by processing conditions. Based on these results, effect of processing conditions and filler content on changing morphologies and properties of the composites is described. (C) 2008 Elsevier Ltd. All rights reserved.