Modification of the Crystallization Behavior of Isotactic Polypropylene by Grafting Styrene Segments

As a typically semicrystalline polymer, the physical properties of isotactic polypropylene (iPP) are directly related toits crystallization. In this work, styrene (St) is grafted onto iPP chains by reactive processing to modify its crystallization behavior.The St grafting segments disrupt the stereoregularity of the iPP chain, leading to the appearance of a gamma-crystal. More interestingly, thepresence of St grafting segments can remarkably increase the crystallization temperature and crystallization rate of iPP and reducethe size of crystals. On the one hand, the rigid structure of benzene rings in St grafting segments can squeeze easily iPP chains toform the relatively ordered structure, which can be further stabilized by the mutual pi-pi conjugation between the benzene rings andthe helix chains of iPP. On the other hand, the St grafting segments locating in the amorphous phase can hinder the growth ofcrystals, which leads tofiner and more crystals.

Automated summary

In this study, styrene was grafted onto isotactic polypropylene (iPP) chains to modify its crystallization behavior. The presence of styrene grafting segments resulted in higher crystallization temperature and rate, as well as smaller crystal size for iPP. The rigid structure of styrene benzene rings promoted the formation of a relatively ordered structure in iPP, while the grafting segments in the amorphous phase hindered crystal growth, leading to finer crystals.