Fracture toughness of elastomer-modified polypropylene: MATERIAL CHARACTERISATION

Abstract

The fracture toughness of impact modified polypropylene (PP) with impact modifier (IM) content up to 30 wt% was measured under quasi-static and impact rates of loading. Three types of IMs were employed in this work, which were all PP/PE based copolymers. Under quasi-static rate of loading, the fracture toughness for blends containing 30 wt% of IM were measured using the specific essential work of fracture ( w e) and the J-integral via the locus method ( J c). Both methods gave similar values of fracture toughness. Furthermore, the type of impact modifier used does not have a strong influence on the w e (or J c) value. The main difference between the three blends is the plastic work term ( βw p). Using the specific essential work of fracture approach, no plane stress–plane strain transition can be observed. For impact rate of loading, the dynamic G c and the Izod impact strength for blends containing 10–30 wt% of IM were measured. All the blends failed in a brittle or semi-brittle manner. In general, G c increases with IM concentration.