Debonding and fracture of particulate‐filled isotactic polypropylene

Abstract

AbstractExperimental data on particulate‐filled polypropylene rupture are presented, with discussion and explanation of the regularities found. The systems studied are characterized by ductile properties of a semi‐crystalline matrix and a low level of interfacial interaction. Polypropylene as a host and aluminum hydroxide particles, without or with anti‐adhesive treatment, were used. Two concentration regions of different debonding micromechanisms were found. At low filler fraction (< 15–20 vol. %) particles debond independently and completely at the initial stages of drawing, and a microhomogeneous flow mechanism takes place. Above a critical filler content, debonding proceeds in a correlated way with the formation of narrow craze‐like deformation zones transverse to the stretching axes. These zones screen new debondings in their neighborhoods, more or less efficiently, dependent upon filler fraction and, hence, the porosity inside crazes and the level of interfacial interaction. Whether microhomogeneous or craze‐like mechanisms occur essentially determines the regularities of further deformation and fracture: localized or macrohomogeneous flow, ductile or quasi‐brittle fracture, the drop or the rise of ultimate strains with increase of particle diameters. A theoretical description of the transition between microhomogeneous and craze‐like mechanisms is proposed.