均聚PP注塑品中虎皮纹的形貌及流变学研究  

Morphology and Rheology Study on Tiger-striped Flow Marks in Injection Molding of Homo-polypropylene

作　　者：鲁明 杨波 彭莉 罗忠富 李成 丁超 LU Ming;YANG Bo;PENG Li;LUO Zhongfu;LI Cheng;DING Chao(Kingfa Science and Technology Co.,Ltd.,Guangdong Guangzhou 510663,China)

机构地区：[1]金发科技股份有限公司,广东广州510663

出　　处：《广州化工》2024年第24期184-188,195,共6页GuangZhou Chemical Industry

摘　　要：虎皮纹是注塑制品中一种常见的外观缺陷,本文从表面微观形貌和流变学行为研究两方面入手,研究了系列不同熔指的无填充和滑石粉填充的均聚PP样品的虎皮纹。微观形貌研究发现,样品光泽区表面平整,对模具的复制良好,而非光泽区则有明显的沿熔体流动方向取向的痕迹,表面粗糙度较高,这表明熔体在非光泽区与壁面发生了相对滑动,这种相对滑动造成了熔体的微观破裂。流变学研究发现,材料分子量分布越宽,熔体弹性越强,剪切变稀程度越高,则越不容易出现虎皮纹,而符合这些条件的材料,由于分子链缠结作用强,也越不容易出现熔体破裂。上述结果说明均聚PP的虎皮纹主要是熔体与模具壁面发生相对滑移造成的,减少壁面滑移造成的熔体破裂可以减轻或者消除虎皮纹缺陷。Tiger-striped flow marks is a common appearance defect in injection molding products.The tiger-stripe defect of injection molding of a series of homo-polypropylene and homo-polypropylene/talc blends with different melt flow rate(MFR)were investigated from both morphology and rheology behavior.It was found that the glossy part of the flow marks had relatively even surface and higher transcription rate.There were obvious traces along the melt flow direction in dull part and resulting a steaky uneven surface.The different surface morphology of glossy and dull part indicated that wall slip occurred between the melt and the mold wall,which led to the microscopic melt fracture.Rheology study revealed that the wider the molecular weight distribution of the polypropylene matrix,the stronger the melt elasticity,the higher the degree of shear thinning,the less likely to appear the tiger-striped flow marks.On the other hand,melt fracture was less likely to appear in such materials due to the strong entanglement of the polymer chains.The above results showed that the tiger-striped flow marks in homo-polypropylene and its blends were caused by the melt wall slip during the injection molding.The“tiger stripes”can be reduced or eliminated by reducing the melt fracture caused by wall slip.

关 键 词：虎皮纹 微观形貌 流变 熔体破裂 

分 类 号：TQ320.66[化学工程—合成树脂塑料工业]