Brittle–ductile transition in PP/EPDM blends: effect of notch radius

The toughness of polypropylene (PP)/ethylene–propylene–diene monomer (EPDM) blends was studied over wide ranges of EPDM content and temperature. In order to study the effect of notch radius ( R), the toughness of the samples with different notch radii was determined from Izod impact test. The results showed that both toughness and brittle–ductile transition (BDT) of the blends were a function of R, respectively. At test temperatures, the toughness tended to decrease with increasing 1/ R for various PP/EPDM blends. Moreover, the brittle–ductile transition temperature ( T BT) increased with increasing 1/ R, whereas the critical interparticle distance (ID c) reduced with increasing 1/ R. Finally, it was found that the different curves of ID c versus test temperature ( T) for different notches reduced down to a master curve if plotting ID c versus T BT m– T, where T BT m was the T BT of PP itself for a given notch, indicating that T BT m– T was a more universal parameter that determined the BDT of polymers. This conclusion was well in agreement with the theoretical prediction.