An investigation on the impact fracture characteristics of EPR toughened polypropylene

The effect of adding ethylene-propylene copolymer (EPR) into polypropylene (PP), with particular emphasis on the impact fracture characteristics, will be presented in this work. The impact fracture characterization techniques used include the notched Izod impact strength, drop-weight dart impact, and the impact fracture toughness G(c). It was observed that different impact velocity needs to be selected for the different techniques in order to ensure a well defined failure situation and to obtain a well defined impact fracture history based on the force-time curves measured during impact. Whenever there was a blunt or sharp notch present, EPR particles dispersed inside the PP matrix can play an effective role as a toughening additive. Linear elastic fracture mechanics (LEFM) approach for the measurement of the impact fracture toughness G(c) can be applied not only to the PP homopolymer, which failed in a brittle manner under a high rate of loading, but was also found to be applicable to EPR modified PP, except that plastic zone correction was required.