Predicting the location of weld line in microinjection-molded polyethylene via molecular orientation distribution
Predicting the location of weld line in microinjection-molded polyethylene via molecular orientation distribution
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通过分子取向分布预测微注射成型聚乙烯中熔接线的位置
DOI：
10.1002/polb.24905
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发表时间：
2019-11-15
影响因子：
--
通讯作者：
Men, Yongfeng
中科院分区：
文献类型：
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作者：
Liao, Tao;Zhao, Xintong;Men, Yongfeng
采用小角X射线散射和广角X射线衍射技术，研究了具有熔接线的微注塑线性低密度聚乙烯的微观结构和分子取向分布随工艺参数的变化规律。熔接线是通过在注射成型中彼此成180度角的两个分离的熔体流的重新组合而引入的。片层结构的形成与模具温度密切相关，而与注射速度和熔体温度关系不大。根据Hermans方程，计算了不同成型条件下，不同位置的分子取向分布。随着模具温度和熔体温度的升高，聚合物链的取向度和取向层的厚度显著降低，这分别可以用剪切链的应力松弛和熔体粘度的降低来解释。当注射速度、模具温度和熔体温度变化时，熔接线中的分子取向水平最低，从而为确定注塑过程中流动障碍物引起的熔接线位置提供了一种有效的手段。(c)2019 Wiley Periodicals，Inc. J.波利姆科学，部分B：聚合物物理学2019
The microstructure and molecular orientation distribution over both the length and the thickness of microinjection-molded linear low-density polyethylene with a weld line were characterized as a function of processing parameters using small-angle X-ray scattering and wide-angle X-ray diffraction techniques. The weld line was introduced via recombination of two separated melt streams with an angle of 180 degrees to each other in injection molding. The lamellar structure was found to be related to the mold temperature strongly but the injection velocity and the melt temperature slightly. Furthermore, the distributions of molecular orientation at different molding conditions and different positions in the cross section of molded samples were derived from Hermans equation. The degree of orientation of polymeric chains and the thickness of oriented layers decrease considerably with an increase of both mold temperature and melt temperature, which could be explained by the stress relaxation of sheared chains and the reduced melt viscosity, respectively. The level of molecular orientation was found to be lowest in the weld line when varying injection velocity, mold temperature, and melt temperature, thus providing an effective means to identify the position of weld line induced by flow obstacles during injection-molding process. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019