writer：Jian Kang, Bin Wang, Hongmei Peng, Jingping Li, Jinyao Chen, Jinggang Gai, Ya Cao, Ming Xiang
keywords：isotactic polypropylene; dual-selective β-nucleating agent; stereo-defect distribution; dynamic crystallization; β–αrecrystallization
source：期刊
specific source：Polymers for Advanced Technologies
Issue time：2013年
The selectivities of different β-nucleating agents might be quite different from each other, which is important in determining the crystallization and properties of the obtainedβ-isotactic polypropylene (β-iPP). However, the relationship between molecular structure and dynamic crystallization behavior of β-iPP nucleated by dualselectiveβ-nucleating agent (DS-β-NA) is still not clear. In this study, the dynamic crystallization and melting behavior of two β-iPP with nearly same average isotacticity but different stereo-defect distribution, nucleated by a DS-β-NA (N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide; trade name TMB-5), were studied by differential scanning calorimetry, wide-angle X-ray diffraction, and scanning electronic microscopy. The results indicated that in the presence of TMB-5, the dynamic crystallization and melting behavior of the samples are quite different because the joint effects of the dual selectivity of TMB-5 and stereo-defect distribution of the iPP under different cooling rates. Two important roles were observed: (i) slow cooling rate favors the formation of highβ-fraction; and (ii) high crystallization temperature favors the crystallization ofα-phase accelerated by TMB-5. Generally, the dual
selectivity of the DS-β-NA, the stereo-defect distribution of iPP, and the cooling rate were important factors in determining the formation of β-crystal.