writer：Zhongzhu Liu, Xianhu Liu, Guoqiang Zheng(通讯作者), Kun Dai, Chuntai Liu, Changyu Shen
keywords：isotactic polypropylene
source：期刊
specific source：Journal of Materials Science, 2015, 50, 599-604
Issue time：2014年

Polymer processing generally plays a crucial role in determining the development of microstructure in the fabricated product. In this paper, isotactic polypropylene (iPP) containing 0.1 wt% b-nucleating agent was extruded via a slit die and immediately melt-stretched upon

various stretching rates (SR) at the die exit. The microstructure of b-nucleated iPP samples was investigated using two-dimensional wide-angle X-ray diffraction and small-angle X-ray scatterings (2D-WAXD/SAXS) measurements. It is observed that, no matter what SR is, lamellar branching of b-form crystal is formed in meltstretched samples, which is scarcely reported in open literatures. A method is proposed to calculate the crystallinity of daughter lamellae in b-crystal (Xb-D). It is found that Xb-D decreases with increasing SR, indicating that lamellar branching of b-form crystal is restrained by higher SR. Such case should be attributed to the denser-oriented structures (e.g., shish) induced by higher SR, leaving a  confined space between adjacent-oriented structures for the growth of daughter lamellae.