Effect of localization of carbon nanotubes on fracture behavior of un-vulcanized and dynamically vulcanized PP/EPDM/MWCNT blend-nanocomposites

Effect of localization of multiwall carbon nanotube (MWCNT) on the fracture toughness and deformation mechanisms of un-vulcanized and dynamically vulcanized polypropylene/ethylene-propylene terpolymer/multiwall carbon nanotube (PP/EPDM/MWCNT) blend-nanocomposites were investigated under both the Izod impact loading and the essential work of fracture (EWF) test as quasi-static loading conditions. The localization of MWCNT in the PP matrix led to increased impact fracture toughness via multiple crazing and crack deviation induced by MWCNT aggregates in the PP matrix, while it had negative effect on the fracture toughness under EWF test condition through hindrance effect on the yielding and necking processes. This contradiction was attributed to the different dominant deformation mechanisms in the PP matrix under high speed multiaxial Izod impact and low speed plane biaxial EWF fracture tests (crazing and shear yielding, respectively). Although the various toughening mechanisms such as nano-bridge mechanism were activated during the fracture processes, vulcanization induced interfacial adhesion improvement between the PP and EPDM particles played the main role in determining of the fracture toughness of the vulcanized blend-nanocomposites.