Abstract: The effect of isobutylene-isoprene rubber(IIR) on the crystallization bebaviol of isotac-tic polypropylene(IPP) and the morphology of the blends have been studied by DSC,WAXD,polarized light microscopy,SEM and mechanical property test.IIR shows a slight influenceon the melting point, crystallinity, crystallization rate of IPP.IIR does not enter into IPPphase in melt state, but shows a retarding action on the growth of IPP crystal and is aneffective nucleating agent for IPP spherulites.The impact strength of the blend increasesrapidly with IIR content greater than 30 parts.The tensile strength of the blend, however.decreases with increase of IIR content.The impact strength of IPP/IIR(100/20) treated atabout 130℃ for 2 hours was 5 times as high as that of the untreated one.

Key words: isotactic polypropylene, butyl rubber, blend, mechanical property, crystallization behavior