Abstract: The effects of rare earth β nuleating agent (β-NA) on the mechanical properties of propylene/ethylene random copolymer (PPR) blends with ethylene-octene copolymer were investigated. Machanical tests suggested that EOC and β-NA improved the impact strength of PPR, and made the brittle-ductile transition temperature (Tbd) of the modified PPR systems move to the lower temprature. In PPR/EOC/β-NA systems, it was obviously to find that β-NA and EOC had synergistic effect on the toughing the blends. The results of the differential scanning calorimetry (DSC) and the Wide angle X-ray diffraction (WAXD) showed that, EOC played a role in the heterogeneous nucleation, and increased the crystallization temperature. On the other hand, there was a transformation of β-PP to α-PP during the impact process for β-NA nucleated samples, and the presence of the EOC prevented such a process, which most likely results in the great improvement of fracture toughness of PPR/EOC/β-NA.

Key words: polypropylene random-copolymer, ethylene-octene copolymer, Rare-earth β nuleating agent, brittle-ductile transition temprature, mechanical property