Investigation on the structure and crystallization behavior of controlled rheology polypropylene with different stereo-defect distribution
writer：Jian Kang, Bin Wang, Hongmei Peng, Jinyao Chen, Ya Cao, Huilin Li, Feng Yang, Ming Xiang
keywords：Controlled-rheology polypropylene; Stereo-defect distribution; Crystallization kinetics
source：期刊
specific source：Polymer Bulletin
Issue time：2013年
Understandings concerning the influence of peroxide degradation on the stereo-defect distribution and related crystallization kinetics of controlled-rheology polypropylene (CRPP) are of great importance. In this study, two iPP samples with similar molecular weight and average isotacticity but different stereo-defect distribution, PP-A, PP-B and their degradation productions after the addition of dicumyl peroxide (DCP) were used. Their Melt flow index (MFI), stereo-defect distribution, crystallization behavior and kinetics were studied using MFI measurement, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), non-isothermal crystallization kinetics and successive self-nucleation and annealing (SSA) fractionation. The results showed that as the content of DCP increased, the MFI, crystallization temperature and crystallization rate of PP increased gradually, the crystallization peak width became narrower, the crystallite size decreased. Meanwhile, the addition of DCP greatly restrained the formation of thick lamellae nd narrowed its the stereo-defect distribution (meso sequence length (MSL) distribution). On the other hand, results showed that PP with different stereo-defect distribution have similar MFI variation after degradation. PP-A (whose stereo-defect distribution was less uniform than PP-B) and its degradation products still possess higher crystallization rate, stronger crystallizability,
smaller crystallite size and higher fractions of long MSL, compared with their counterparts of PP-B.