Oriented structure in stretched isotactic polypropylene melt and its unexpected recrystallization: optical and X-ray studies
Oriented structure in stretched isotactic polypropylene melt and its unexpected recrystallization: optical and X-ray studies
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DOI：
10.1002/pi.3097
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发表时间：
2011-10
影响因子：
3.2
通讯作者：
G. Zheng;Z. Jia;Songwei Li;K. Dai;Baochen Liu;Xiaoli Zhang;Liwei Mi;Chuntai Liu;Jingbo Chen;Changyu Shen;Xiangfang Peng;Qian Li
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文献类型：
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作者：
G. Zheng;Z. Jia;Songwei Li;K. Dai;Baochen Liu;Xiaoli Zhang;Liwei Mi;Chuntai Liu;Jingbo Chen;Changyu Shen;Xiangfang Peng;Qian Li
在极小的挤出速率下，通过挤出机的狭缝模头挤出全同立构聚丙烯熔体。同时，挤出的熔体在模头出口处以各种拉伸速率（SR）拉伸。利用偏光显微镜、二维广角X射线散射和小角X射线散射研究了取向结构及其通过自引晶随后的再结晶。正如预期的那样，更细长和更致密的取向结构形成在较大的SR，这表明取向优选地促进与增加SR。在重结晶过程中开发的结晶形态的情况下，通过退火后幸存的取向结构检索shish烤肉串状结构。出乎意料的是，对于在较高SR下拉伸的片材，观察到主要稀疏且短的串晶结构。对于在较低SR下拉伸的片材，观察到致密且长的串状结构。这表明，在较低的SR拉伸的片材中的取向结构具有更好的热稳定性比在较高的SR拉伸的片材。这是讨论的基础上，相对于不同的链长的拉伸网络中的纠缠结的松弛。版权所有© 2011化学工业协会
At an extremely small extrusion rate, an isotactic polypropylene melt was extruded through a slit die of an extruder. Simultaneously, the extruded melt was stretched at various stretching rates (SRs) at the die exit. The oriented structure and its subsequent recrystallization via self-seeding were investigated using polarized optical microscopy, two-dimensional wide-angle X-ray scattering and small-angle X-ray scattering. As expected, much slenderer and denser oriented structures were formed at larger SR, which indicates that orientation is preferably promoted with increasing SR. In the case of the crystalline morphology developed during recrystallization, a shish kebab-like structure was retrieved via the surviving oriented structure after annealing. Unexpectedly, for the sheet stretched at higher SR, a mainly sparse and short shish kebab structure was observed. For the sheet stretched at lower SR, a dense and long shish kebab structure was observed. This suggests that the oriented structure in the sheet stretched at lower SR has a better thermal stability than that in the sheet stretched at higher SR. This is discussed based on the relaxation of entangled junctions in the stretched networks with respect to varying chain length. Copyright © 2011 Society of Chemical Industry