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[摘要]：The roles of compositional heterogeneity and phase structure oil an unusual shear-enhanced crystallization behavior of impact-resistant polypropylene copolymer (IPC) were systematically investigated by differential scanning calorimetry (DSC), polarized optical micro-copy (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. |
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