writer：Xianhu Liu, Kun Dai, Xiaoqiong Hao, Guoqiang Zheng(通讯作者), Chuntai Liu, Dirk W. Schubert, and Changyu
keywords：Xianhu Liu, Kun Dai, Xiaoqiong Hao, Guoqiang Zheng(通讯作者), Chuntai Liu, Dirk W. Schubert, and Changyu Shen
source：期刊
specific source：Industrial Engineering and Chemical Research
Issue time：2013年
Although both shear flow and β-nucleating agent (β-NA) could separately induce β-crystal in isotactic
polypropylene (iPP), their combination, particularly in the typical industrial processes, in fact has received comparatively little
attention. In the current study, two-dimensional wide-angle X-ray diffraction and small-angle X-ray scattering (2D-WAXD/
SAXS) measurements were performed to investigate the effect of β-NA on the crystalline structure of the oriented shear zone in
injection molded iPP. It is observed that, regardless of the β-NA concentration, parent?daughter structure of α-crystal can be
formed in iPP. Furthermore, the fraction of daughter lamellae elevates with the increasing concentration of β-NA. Interestingly,
unexpected scattering patterns of (300) reflection for β-crystal, which is similar with that for parent?daughter lamellar branching
of α-crystal, is exclusively found in iPP with higher concentration of β-NA (1.0 wt %). The most possible explanation is that the
addition of high content of β-NA lowers the free energy barrier. Additionally, the same change tendency of long period, crystal
lamellar thickness and lateral dimension, d-spacing and crystallite size is found, viz., they first increase and then decrease with the
increasing β-NA content. The results demonstrate that the concentrations of β-NA have a significant effect on the crystal grain
structure under the practical molding process.