Crystalline Structure of Injection Molded 尾-Isotactic Polypropylene: Analysis of the Oriented Shear Zone

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• 作者：Xianhu Liu ; Kun Dai ; Xiaoqiong Hao ; Guoqiang Zheng ; Chuntai Liu ; Dirk W. Schubert ; Changyu Shen
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2013
• 出版时间：August 28, 2013
• 年：2013
• 卷：52
• 期：34
• 页码：11996-12002
• 全文大小：374K
• 年卷期：v.52,no.34(August 28, 2013)
• ISSN：1520-5045

文摘

Although both shear flow and 尾-nucleating agent (尾-NA) could separately induce 尾-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 尾-NA on the crystalline structure of the oriented shear zone in injection molded iPP. It is observed that, regardless of the 尾-NA concentration, parent鈥揹aughter structure of 伪-crystal can be formed in iPP. Furthermore, the fraction of daughter lamellae elevates with the increasing concentration of 尾-NA. Interestingly, unexpected scattering patterns of (300) reflection for 尾-crystal, which is similar with that for parent鈥揹aughter lamellar branching of 伪-crystal, is exclusively found in iPP with higher concentration of 尾-NA (1.0 wt %). The most possible explanation is that the addition of high content of 尾-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 尾-NA content. The results demonstrate that the concentrations of 尾-NA have a significant effect on the crystal grain structure under the practical molding process.