Essential work of fracture (EWF) analysis for polypropylene grafted with maleic anhydride modified polypropylene/calcium carbonate composites

The essential work of fracture (EWF) method was employed to determine the fracture behavior of calcium carbonate (CaCO3) filled polypropylene (PP) composites with and without polypropylene grafted with maleic anhydride (PP-g-MA) incorporated. The effect of composition on the EWF parameters of the composites was particularly investigated. It was found that the plane-stress EWF approach worked well for the pure PP, PP/CaCO3 and PP/CaCO3/PP-g-MA composites. The specific essential work of fracture, we, of PP/CaCO3 composites was appreciably lower than that of pure PP, while the specific plastic work item, βwp, decreased markedly with increasing CaCO3 content. For the composites modified with PP-g-MA in which the mass ratio of PP to CaCO3 was fixed, we increased considerably at first and then decreased with increasing amount of PP-g-MA. It was noted that the we value of PP/CaCO3/PP-g-MA at a mass ratio of 80/20/3 was about 4 KJ/m2 higher than that of PP/CaCO3, and even higher than that of pure PP. However, all βwp values for the hybrid composites with different content of PP-g-MA were lower than that of the PP/CaCO3 composites. In addition, the specific work of fracture for yielding (we,y and β′wp,y) and that for necking and subsequent fracture (we,n and β″wp,n) obtained based on the partition of the specific work were also analyzed. It was found that the dominant factors which affected we and βwp for the studied systems were the necking terms, as a majority of fracture energy was dissipated in the necking and fracture process.