Role of morphology and coupling agent in fracture performance of glass‐filled polypropylene

The effect of silane coupling agent on the morphology and fracture performance of particulates‐filled polypropylene was investigated. The onset of the crystallization at the filler‐matrix interface was observed by optical microscopy. This analysis shows that the silane alters the matrix morphology by inducing nucleation at the filler‐matrix interface. This effect was attributed to the physisorbed layer of silane on the filler. The fracture performance of the composites was analyzed by the post yield fracture mechanics approach. The effect of coupling agent on the fracture performance was found to occur at a very low concentration, whereas subsequent increase in silane concentration had no effect. Furthermore, the effect of coupling agent depended on concentration of filler. Silane treatment had a detrimental effect at low concentration of filler. However, at high concentration of filler, an improvement in the filler‐matrix adhesion had a beneficial effect on the fracture performance. Two phenomena, the morphological effect and the competition between the contribution of the matrix‐filler interface and the contribution of the matrix, were found to be possible explanations for the variation of K Rmax with filler concentration and adhesion at the matrix‐filler interface.