Abstract:

The effects of melt flow behavior and adjacent weld line formation behind the obstacle on the flow induced birefringence in the weld line region of the parts were investigated.Polystyrene parts with weld lines were injection-molded under various process conditions by means of a specially designed plate cavity with an obstacle.The photo-elasticity method was used to determine the gapwise-averaged birefringence along the flow direction of injection-molded parts.The results showed that melt temperature and packing pressure had a significant impact on the birefringence distribution of the molded parts.Birefringence pattern around the weld line region just behind the obstacle was apparently different from other regions of the part, which was attributed to the local flow behavior and molecular orientation distribution after the melt flow fronts met.The maximum value of gapwise-averaged birefringence along the weld line occurred at a small distance from the obstacle.Heat shrinkage test results of different locations at the adjacent weld line region were also consistent with the above results.

Key words:

注射成型, 熔接线, 双折射, 光弹, 热收缩, 分子取向

摘要：

带有熔接线的透明聚苯乙烯平板制品通过带嵌件的模具注射成型，利用光弹测试考察了不同工艺条件下的制品双折射行为，探讨了嵌件造成的相邻熔接线区域熔体流动行为及对制品双折射分布的影响。结果表明，保压压力和熔体温度对制品双折射整体分布影响明显;嵌件后熔接缝区域与制品其他区域的双折射行为有较大差异，其变化与熔体相遇后流动行为和熔接部位分子取向分布有关;制品最大双折射值出现在嵌件后一定距离处。热收缩实验进一步验证了上述结果。

关键词:

注射成型, 熔接线, 双折射, 光弹, 热收缩, 分子取向