Crystallization behavior and morphology of β-nucleated isotactic polypropylene with different stereo-defect distribution
作者：Zhengfang Chen, Bin Wang, Jian Kang, Jinyao Chen, Feng Yang, Ya Cao, Huilin Li, Ming Xiang
關鍵字：β-nucleated isotactic polypropylene; crystallization behavior; crystalline morphology
論文來源：期刊
具體來源：Polymers for Advanced Technologies
發(fā)表時間：2013年
Aiming at further investigate the combination effect of concentration of
β-nucleating agent (β-NA) and stereo-defect distribution on the crystallization
behavior of β-nucleated isotactic polypropylene (β-iPP), in this study, the
crystallization behavior and polymorphic morphologyof twoβ-iPP resins with nearly
same average isotacticity (PP-A and PP-B) but different uniformities of stereo-defect
distribution were investigated by differential scanning calorimetry (DSC), wide angel
X-ray diffraction (WAXD) and polarized optical microscopy (POM). The results of DSC and WAXD showed that the addition of TMB-5 increases the crystallization temperature and decreases the spherulite sizes of both PP-A and PP-B, and reduces their crystallization energy barriers as well; however, the polymorphic behaviors of PP-A and PP-B exhibit different dependence on the TMB-5 concentration. For PP-A with less uniform distribution of stereo-defects, β-phase can be observed only when the TMB-5 concentration is no less than 0.1wt%, while for PP-B with more uniform stereo-defect distribution, addition of 0.01wt% TMB-5 can induce the formation of β-phase. Moreover, the analysis of POM indicated that the crystalline morphologies of both PP-A and PP-B change greatly with the TMB-5 concentration, and the variation features of PP-A and PP-B are quite different from each other. PP-B with more uniform stereo-defect distribution was more favorable for the formation of large amount of β-phase in the presence of wide concentration range of TMB-5. The different polymorphic behaviors and their different dependences on the β-NA concentration were related to the different uniformities of stereo-defect distribution of the samples, since the distribution of stereo-defects could restrain the regular insertion of molecular chains during crystallization and thus determine the tendency the α-phase crystallization of the sample.