Abstract: Effect of a rare earth β-nucleating agent(WBG)on the properties of isotactic polypropylene (iPP) was studied by polarizing microscope(PLM), differential scanning calorimetrv( DSC), and wide-angular X-ray diffraction( WAXD).The results showed that the addition of small amounts of WBG to PP induced the proportion of β crystals. The relative content of β-phase was up to 57 % in a PP containing 0.2% ofthe WBG. The Izod impact strength of homopolymerization PP was increased 1.48 times, and heat deflection temperature rose 11~33℃，when small amounts of WBG was added. The samples showed the optimal properties when the beat treatment at 100 ℃. A slow cooling rate benefited the for mation and perfect of pcrystals. The photos of PLM showed a new phenomenon that β crystals grew up with leaflike form in the center and covered with B-spherulites which formed some small and anomalistic interface,some central β crystals impenetrate each other.

Key words: rare earth;nucleating agent, βcrystallite, isotactic polypropylene, heat treatment