Fracture of polypropylene: The effect of crystallinity

Abstract

The effect of crystallinity on the fracture behaviour of polypropylene was studied under impact conditions. The crystallinity was varied by taking low- and high-isotactic polypropylenes and mixtures thereof. The crystallinity ranged from 31 to 53 wt%. The fracture behaviour was studied as a function of temperature by means of a tensile test on notched Izod bars at 1 m s −1. The brittle-to-ductile transition temperature ( T bd) increases with increasing crystallinity, which is primarily attributed to the increasing yield stress. In the case of brittle fracture, the fracture energy decreases with increasing crystallinity. In the case of ductile fracture, the fracture energy seems to remain constant, irrespective of the crystallinity.