The role of interlamellar chain entanglement in deformation-induced structure changes during uniaxial stretching of isotactic polypropylene
The role of interlamellar chain entanglement in deformation-induced structure changes during uniaxial stretching of isotactic polypropylene
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DOI：
10.1016/j.polymer.2007.08.065
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发表时间：
2007-11
期刊：
影响因子：
4.6
通讯作者：
F. Zuo;J. Keum;Xuming Chen;B. Hsiao;Hongyu Chen;S. Lai;R. Wevers;Jing Li
中科院分区：
文献类型：
--
作者：
F. Zuo;J. Keum;Xuming Chen;B. Hsiao;Hongyu Chen;S. Lai;R. Wevers;Jing Li
采用原位小角x射线散射（SAXS）和广角x射线衍射（WAXD）研究了不同温度（室温、60℃和160℃）下等规聚丙烯（iPP）薄膜在单轴拉伸过程中变形引起的结构变化。根据WAXD数据，估计了非晶相、亚晶相和晶相的质量分数。结果表明：室温下，主要的结构变化是单斜α-型折叠链晶片向定向介晶相转变；而在高温下（bbb60℃）；主要的变化是非晶相向取向折叠链晶片的转变。这种行为可以用层间非晶链纠缠网络的相对强度来解释，这可能直接影响链的分布，以及周围的晶片。结果表明，在低温拉伸过程中，片层间的缠结网络较强，可导致片层断裂，形成定向的中晶相。而在高温拉伸过程中，链解缠过程占主导地位，导致约束链松弛，形成更多的折叠链片。
In-situ small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD) were carried out to investigate the deformation-induced structure changes of isotactic polypropylene (iPP) films during uniaxial stretching at varying temperatures (room temperature, 60°C and 160°C). From the WAXD data, mass fractions of amorphous, mesomorphic and crystal phases were estimated. Results indicate that at room temperature, the dominant structure change is the transformation of folded-chain crystal lamellae (monoclinic α-form) to oriented mesomorphic phase; while at high temperatures (>60°C); the dominant change is the transformation of amorphous phase to oriented folded-chain crystal lamellae. This behavior may be explained by the relative strength between the interlamellar entangled network of amorphous chains, which probably directly influence the tie chain distribution, and the surrounding crystal lamellae. It appears that during stretching at low temperatures, the interlamellar entanglement network is strong and can cause lamellar fragmentation, resulting in the formation of oriented mesomorphic phase. In contrast, during stretching at high temperatures, the chain disentanglement process dominates, resulting in the relaxation of restrained tie chains and the formation of more folded-chain lamellae.