Characterization of maleic anhydride/styrene melt-grafted random copolypropylene and its impact on crystallization and mechanical properties of isotactic polypropylene

Abstract

Maleic anhydride/styrene-grafted random copolypropylene (MPP) was prepared by multi-monomer melt grafting. Fourier transform infrared spectroscopy verified that maleic anhydride and styrene were successfully grafted onto the polypropylene random copolymer (PPR) backbones. Dynamic rheological tests indicated the existence of long branched chains on MPP. The influence of grafting degree of maleic anhydride on the crystallization behavior of MPP was investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. The results showed that the crystallization rate of MPP was higher than that of PPR, and it increased with the increase in grafting degree. The long-chain branched structure could promote heterogeneous nucleation formation of MPP, resulting in the increase in crystallization rate and the decrease in spherulite size. Moreover, the effect of MPP content on crystallization and mechanical properties of isotactic polypropylene (PP)/MPP blends was further investigated. It was found that the interfacial interaction in the blends with 1–10 wt% of MPP was higher than PP/MPP-15% blend. Introducing MPP into PP could induce the formation of β-crystal. Consequently, the incorporation of MPP into PP increased the tensile strength and impact strength and maximum values were obtained for PP/MPP-10% blend.