Effect of polystyrenes with different architectures on the -nucleating efficiency and toughening of isotactic polypropylene

The effect of polystyrenes (PSs) with different architectures (three-arm star-shaped polystyrene (sPS), comb-like branched polystyrene (cPS) and linear polystyrene) on their -nucleating efficiency for isotactic polypropylene (iPP) during crystallization and final impact and the tensile properties of iPP/PS blends were investigated by dynamic rheological measurements, SEM, DSC, polarized optical microscopy, wide angle X-ray diffraction and mechanical property measurements. The results show that the architecture of PS has marked influence on its dispersibility in iPP and -nucleating efficiency. For iPP/cPS blend, plenty of short side chains reduce the probability of cPS chain entanglements, facilitating the interdiffusion between iPP and cPS chains. A favorable interfacial interaction results in good dispersibility, high nucleating efficiency and an excellent toughening effect of cPS on iPP. However, the relatively high chain entanglement degree of sPS may not be in favor of chain diffusion between iPP and sPS and therefore relatively poor dispersibility and toughening effect are obtained. The elongation at break and impact strength of iPP were dramatically improved, especially with the addition of 1 wt% cPS. The toughening mechanism of PS on iPP is the dissipated energy caused by cavitation and the -nucleating effect of PS. (c) 2018 Society of Chemical Industry