(398bw) Crystallization and Foaming Behaviors of Modified Polypropylene by Phenyl-contained Function Group

Polypropylene (PP) foam has a wide application in many fields such as package, transportation, and architecture due to its excellent mechanical and thermal properties. However, PP as a semicrystalline polymer is very difficult to foaming because its very low melting strength would cause cell collapse. Hence, a meliorating foaming of PP through improving its crystallization behavior was put forward. In this work, phenyl-contained function group was grafted onto PP chain through melting grafting reaction, which showed that branched chain resulting from only benzene in sequence can increase dramatically the crystal density and decrease significantly the crystal size¹. Length and density of the branched chain also have effect on the crystallization properties² because of the steric hindrance to the ordered packing of PP backbones chains, and a reduction in crystallinity was observed. A batch foaming process including melting, cooling, isothermal saturation, and foaming stages was utilized to produce PP foams. The formed small and dense crystal at isothermal saturation stage could not only act as a strong heterogeneous nucleation for PP foaming but also hinder the growth of bubbles so that microcellular PP foam could be obtained. Moreover, it could also enhance the limiting upper foaming temperature to 160 ºC.

Keywords: microcellular foam, phenyl modified polypropylene, crystallization

References:

[1] Shuai Zhou, Shicheng Zhao, Zhong Xin, Polymer Engineering & Science. 2015, 55, 2

[2]Fengmei Su, Youxin Ji, Lingpu Meng, Zhen Wang, Zeming Qi, Jiarui Chang, Jianzhu Ju, Liangbin Li, Macromolecules.2017, 50, 5