Effect of cooling rate, particle size and volume fraction on non-isothermal crystallization of polypropylene/silica nanocomposite

Thermoplastic nanocomposites of maleic anhydride grafted polypropylene (MA-g-PP) and monodisperse silica-nanospheres of diameter 60, 100 and 250nm have been prepared by melt blending in a twin screw micro-compounder. The tensile specimens are molded and tested using digital image correlation technique. The crystallinity has been determined using differential scanning calorimetry (DSC) and wide angle X-ray diffraction. The scanning and transmission electron micrographs show proper dispersion of silica-nanospheres in the matrix. Taguchi method has been employed for the analysis of non-isothermal crystallization parameters. The crystallization parameters are calculated from DSC plots. It is found from S/N ratio analysis that the increase in nanoparticle size leads to higher crystallinity, onset and peak temperature whereas reverse effect is observed for increase in cooling rate. The effect of volume fraction is less pronounced. Further it is found that the dependence of mechanical properties on interface between matrix and reinforcement is more decisive than crystallinity of nanocomposite