Initiation of cavitation upon drawing of pre-oriented polypropylene film: In situ SAXS and WAXD studies
Initiation of cavitation upon drawing of pre-oriented polypropylene film: In situ SAXS and WAXD studies
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预取向聚丙烯薄膜拉伸时空化的引发：原位 SAXS 和 WAXD 研究
DOI：
10.1016/j.polymer.2017.09.017
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发表时间：
2017-10-16
期刊：
影响因子：
4.6
通讯作者：
Men, Yongfeng
中科院分区：
文献类型：
--
作者：
Xiong, Bijin;Kang, Jian;Men, Yongfeng
通过原位小角X射线散射（SAXS）和广角X射线衍射（WAXD）技术研究了预取向聚丙烯薄膜拉伸时的空化引发。通过SAXS和WAXD实验分别估算了空化和晶体剪切应力的宏观应变。通过比较晶粒尺寸（cs）和晶粒尺寸（cav），揭示了纵向拉伸时在空泡形成之前存在局部晶体剪切。在MD方向上，空洞的初始尺寸大于晶体薄片的长周期，而在横向上的尺寸与子薄片的相对分数成反比。宏观临界应力的空化σ（cav）和晶体剪切σ（cs）的启动已估计以及。临界应力σ（cav）与结晶度无关，而σ（cs）随结晶度的增加而增加。提出了空化起始的机理，即空化是由子层锚点处的结晶层破裂而起始的。(C)2017爱思唯尔有限公司版权所有
Initiation of cavitation upon drawing of pre-oriented polypropylene films has been investigated via insitu small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. The macroscopic strains for the initiation of the cavitation epsilon(cav) and for the initiation of crystal shear epsilon(cs) have been estimated from in-situ SAXS and WAXD tests respectively. Local crystal shear appears before cavitation upon drawing in machine direction (MD) has been revealed via comparison of epsilon(cs) and epsilon(cav). The initial size of the cavities in MD is larger than the long period of crystalline lamellae while the size in transverse direction is inversely proportional to the relative fraction of daughter lamellae. Macroscopic critical stresses for the initiation of cavitation sigma(cav) and for the initiation of crystal shear sigma(cs) have been estimated as well. The critical stress sigma(cav) is independent on the crystallinity, whereas sigma(cs) increases with increasing crystallinity. The mechanism for the initiation of cavitation has been proposed, i.e. the cavitation is initiated by the breakage of crystalline lamellae at the anchor point of the daughter lamellae. (C) 2017 Elsevier Ltd. All rights reserved.