微发泡注塑成型PC制件的表面缺陷及形态分析

Surface Defects and Morphology of Microcellular Injection Molded PC Parts

微发泡注塑成型制品常有漩涡状流痕和银纹两类表面缺陷。漩涡状流痕与均相溶液的流动形态关系密切,多在浇口附近;而银纹多在远离浇口处。文中利用扫描电子显微镜(SEM)对微发泡注塑成型聚碳酸酯(PC)制品的漩涡状流痕、银纹及泡孔形态进行观察,发现微孔形态和表面缺陷之间存在如下关系:漩涡状流痕对应的气泡剪切变形较小,而银纹相关的气泡剪切变形较大;根据气泡SEM的形态,银纹可细分为银带纹、银丝纹。剪切变形大、不破裂气泡表面形成银带纹,破裂则形成银丝纹。

Swirl marks and silver streaks are two popular surface defects of microcellular injection molded parts. Both swirl marks and silver streaks relate to flow state of single-phase solution that is made of polymer melt and supercritical fluid （SCF）. Swirl marks usually locate near gate and silver streaks appear the filling end. Based on scanning electron microscope （SEM） experimental results of microcellular injection molded polycarbonate（PC） parts,the swirl marks,silver streaks and their morphology were studied in this paper. It is found that swirl marks with less cell deformation compared with silver streaks. According to the cell morphology of silver streak surface and cross-section,silver streak could be divided into silver strip and silver thread two different types. The former is composed of solidification polymer with shear-stress stretching gas cell in narrow ellipse shape. And the later is composed of solidification polymer with broken gas cell. To distinguish silver strip and silver thread,stretching gas cell broken or not is the criterion.