Citation

Shijie Song, Jiachun Feng*, Peiyi Wu, and Yuliang Yang. Shear-Enhanced Crystallization in Impact-Resistant Polypropylene Copolymer: Influence of Compositional Heterogeneity and Phase Structure. Macromolecules 2009, 42, 7067-7078.

Abstract

The roles of compositional heterogeneity and phase structure on an unusual shear-enhanced crystallization behavior of impact-resistant polypropylene copolymer (IPC) were systematically investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), field emission transmission electron microscopy (FETEM), and scanning electronic microscopy (SEM). Upon an interval of preshearing, we observed an amazing accelerated crystallization in IPC, whereas no such shear-enhanced crystallization was found in isotactic polypropylene (iPP) or iPP/ethylene−propylene random copolymer (EPR) blend after the same shearing. By solvent and thermal fractionation, the effects of components in IPC on shear-enhanced crystallization were clarified. We hypothesize that this phenomenon is a consequence of phase structure changes induced by shearing that releases the partially crystalline block copolymer from amorphous random copolymer which is in favor of a fast crystallization for IPC. We built up a multilayered phase structure of IPC, and by combining the changes in phase structure observed before and after shearing, we present a conceptual model describing the mechanism that account for the significant shear-enhanced crystallization in IPC.