Largely enhanced fracture toughness of the PP/EPDM blends induced by adding carbon nanofibers

In this work, a small quantity of carbon nanofibers (CNFs) were incorporated into polypropylene/ethylene-propylene-diene terpolymer (PP/EPDM) blends. The effects of CNF content on the processing flowability, the microstructure of PP matrix and the morphology of elastomer particles were investigated. The results showed that the processing flowability of the material was not apparently influenced. The straight CNFs selectively located in the PP matrix and exhibited oriented dispersion along the flow direction of melt during the injection molding processing. CNFs exhibited nucleation effect on crystallization of PP. Homogeneous EPDM particles with smaller particle diameters were obtained in the blend composites. Mechanical properties measurements showed that the largely enhanced fracture toughness was achieved for the blend composites and the brittle-ductile transition was induced at lower EPDM content. Specifically, incorporating only 0.2 wt% CNFs into the PP/EPDM (85/15), the impact strength was enhanced about 246%. Further results showed that for the blend which exhibited brittle-fracture feature, the brittle-ductile transition could also be induced with increasing CNF content. The toughening mechanisms were then proposed.