Morphology evolution and crystalline structure of controlled‐rheology polypropylene in micro‐injection molding
Morphology evolution and crystalline structure of controlled‐rheology polypropylene in micro‐injection molding
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DOI：
10.1002/pat.3696
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发表时间：
2016-04
影响因子：
3.4
通讯作者：
Mengjue Li;Y. Qi;Zhongguo Zhao;Zhang Xiang;X. Liao;Yanhua Niu;Miqiu Kong
中科院分区：
文献类型：
--
作者：
Mengjue Li;Y. Qi;Zhongguo Zhao;Zhang Xiang;X. Liao;Yanhua Niu;Miqiu Kong
用偏光显微镜、扫描电子显微镜、差示扫描量热仪和广角X射线衍射仪研究了不同熔体粘弹性的可控流变性聚丙烯(CRPP)的微观结构演变。结果表明，随着过氧化氢的加入，CRPP微型件形成典型的“皮-芯”结构，取向层厚度显著减小。取向层的厚度和不同层的分布强烈依赖于熔体的流动特性和相应的松弛时间(λ)。此外，主要从流变学和热力学的角度探讨了微注射成型过程中抑制取向层形成的机理。结果表明，剪切诱导取向是形成定向分子结构(排核)的关键因素之一。定向层的最终厚度是定向行为和定向行为竞争的结果。版权所有©2015 John Wiley&Sons，Ltd.
In this paper, the microstructural evolution of controlled-rheology polypropylene (CRPP) with different melt viscoelasticities was investigated by polarized optical microscopy, scanning electronic microscopy, differential scanning calorimeter, and wide-angle X-ray diffraction. It is found that a typical “skin-core” structure formed in CRPP microparts and the thickness of oriented layer of CRPP microparts decreases notably with the addition of peroxide. The thickness of oriented layer and the distribution of different layers strongly depend on the melt flow properties and the corresponding relaxation time (λ). Furthermore, the mechanisms of the suppressed formation of oriented layers during the micro-injection molding process are discussed mainly from the viewpoint of rheology and thermodynamics. It is revealed that the shear-induced orientation is one of the key factors for the formation of oriented molecular structure (row nuclei). The final thickness of the oriented layer is the result of the competition between the orientation behavior and the disorientation behavior. Copyright © 2015 John Wiley & Sons, Ltd.