In situ SAXS analysis of extended-chain crystallization during melt-drawing of ultra-high molecular weight polyethylene
In situ SAXS analysis of extended-chain crystallization during melt-drawing of ultra-high molecular weight polyethylene
复制标题
DOI：
10.1016/j.polymer.2007.10.018
复制
发表时间：
2007-11-30
期刊：
影响因子：
4.6
通讯作者：
Uehara, Hiroki
中科院分区：
文献类型：
--
作者：
Kakiage, Masaki;Sekiya, Miho;Uehara, Hiroki
采用同步辐射X射线散射技术，在SPring-8装置上对超高分子量聚乙烯（HDPE）熔体拉伸过程中的相演变进行了原位分析。具有不同缠结特性的膜通过将具有1.07 × 10（7）（较高）和1.73 × 10（6）（较低）的粘度平均MW的较高和较低MW样品溶液共混，然后在180 ℃下压缩模塑来制备。与共混比无关，拉伸应力曲线的平台应力区起始点的赤道上出现了由伸展链晶体（ECC）引起的强烈条纹，这是熔体拉伸的特征之一。对这些条纹的一系列详细分析表明，在熔体拉伸过程中形成了两种不同尺寸的组分：一种是初级ECC，另一种是成熟ECC。这两个ECC组件同步增长的平台应力区的起点为两个电影，独立的纠缠特性的电影。然而，这种同步生长的时间是较长的膜与较低的MW组分比仅含有较高的MW组分的膜。通过透射电子显微镜观察到的熔融拉伸样品的所得形貌也反映了这些特征。这些结果表明，分子缠结特性主导的独特的结晶机制，形成不同尺寸的ECC在熔融拉伸过程中的EST-PE。(c)2007爱思唯尔有限公司保留所有权利。
Phase development during melt-drawing of ultra-high molecular weight polyethylene (UHMW-PE) was analyzed by in situ small-angle X-ray scattering measurements using synchrotron radiation at the SPring-8. Films with different entanglement characteristics were prepared by solution blending of higher and lower MW samples with a viscosity average MW of 1.07 x 10(7) (higher) and 1.73 x 10(6) (lower), followed by compression molding at 180 degrees C. Independent of blend ratio, the strong streak attributed to extended-chain crystals (ECCs) appeared on the equator at the beginning point of the plateau stress region in the stress profile, which was one of the characteristic features of melt-drawing. A series of detailed analyses of these streaks suggested that two components with different dimensions were formed during melt-drawing: one was a precursory ECC, and the other was a mature ECC. These two ECC components grew synchronously at the beginning point of the plateau stress region for both films, independent of the entanglement characteristics of the film. However, the time of this synchronized growth was longer for the film with the lower MW component than for the film containing only the higher MW component. The resultant morphologies of the melt-drawn samples observed by transmission electron microscopy also reflected these characteristics. These results demonstrate that molecular entanglement characteristics dominate the unique crystallization mechanism that forms ECCs with different dimensions during melt-drawing of UHMW-PE. (c) 2007 Elsevier Ltd. All rights reserved.