文献类型：期刊文献

英文题名：Unique crystallization behavior of isotactic polypropylene in the presence of L-isoleucine and its inhibition and promotion mechanism of nucleation

作者：Peng, Xiaoshan[1];Xin, Zhong[1];Zhao, Shicheng[1];Zhou, Shuai[1];Shi, Yaoqi[1];Ye, Chunlin[2]

机构：[1]East China Univ Sci & Technol, Dept Prod Engn, Shanghai Key Lab Multiphase Mat Chem Engn, Shanghai 200237, Peoples R China;[2]Shanghai Res Inst Chem Ind, Shanghai 200062, Peoples R China

年份：2018

卷号：135

期号：10

外文期刊名：JOURNAL OF APPLIED POLYMER SCIENCE

收录：;EI(收录号：20174504376479);WOS:【SCI-EXPANDED(收录号:WOS:000417601900022)】；

基金：The authors gratefully acknowledge the financial support of this work by National Key R&D Program of China (2016YFB0302201), National Natural Science Foundation of China (Grants 21476085 and 21606084), and the Fundamental Research Funds for the Central Universities (222201717025).

语种：英文

外文关键词：crystallization; extrusion; polyolefins

摘要：L-Isoleucine (L-Ile) was identified as an efficient anti-nucleating agent for isotactic polypropylene (iPP). At 0.08 wt %, L-Ile could significantly decrease the peak crystallization temperature (T-cp) of iPP by up to 8 degrees C at a cooling rate of 20 degrees C/min. Furthermore, L-Ile exhibited both anti-nucleation and pro-nucleation abilities; i.e., a low content of L-Ile inhibited iPP crystallization, whereas a high content promoted iPP crystallization. The unique crystallization behavior of iPP in the presence of L-Ile was investigated by differential scanning calorimetry, polarized optical microscopy (POM), and rheological measurement. According to POM, a low content of L-Ile completely dissolved in the iPP melt, whereas a high content of L-Ile did not. Therefore, a mechanism by which L-Ile inhibits and promotes the nucleation of iPP was proposed. Dissolving L-Ile molecules in the iPP melt hindered the homogeneous nucleation of iPP as a "dilution effect"; however, as the content increases, L-Ile could not be completely dissolved in molten iPP, and the residual crystals of L-Ile thus provided heterogeneous nucleation sites for iPP and further promoted its crystallization. Experimental evidence from rheology and POM supported this mechanism. (C) 2017 Wiley Periodicals, Inc.