Effect of high density polyethylene addition and testing temperature on the mechanical and morphological properties of polypropylene/ethylene-propylene diene terpolymer binary blends

High density polyethylene (HDPE) was added to the polypropylene (PP)/ethyle ne-propylene diene terpolymer (EPDM) binary blend, and the effect of testin g temperatures on the modulus of elasticity, impact behavior and correspond ing fracture morphology was analyzed. Modulus of elasticity generally decre ased as the EPDM content increased regardless of the testing temperatures. However, it was found that the modulus of elasticity of PP/EPDM/HDPE ternar y blend increased compared to PP/EPDM binary blend when tested at -30 and - 60 degrees C. Notched Izod impact strength changed depending on the testing temperatures, however, there was not much difference between binary and te rnary blends up to 20 wt% EPDM. However, at more than 30 wt% EPDM content, ternary blends showed higher impact strength compared to binary blends. Esp ecially, at -30 degrees C, brittle-ductile transition was observed between 20 and 30 wt% EPDM. Subsurface morphology was also analyzed, and the relati onship between the impact strength and the stress whitening zone was invest igated. Scanning electron microscopy observation of impact fractured surfac es was conducted, and overall morphology was analyzed with respect to HDPE addition and testing temperature change. (C) 2000 Kluwer Academic Publisher s.