微孔发泡模内表面装饰复合成型工艺的气泡长大过程的动态演变

Dynamic Evolution of Bubble Growth Process in a Combined In-Mold Surface Decoration and Microcellular Foaming

微孔发泡模内表面装饰复合成型是将微孔发泡注射成型与模内表面装饰复合成型的新工艺,与常规微孔发泡注射成型相比,由于覆膜的嵌入在模具型腔内产生非平衡的差异性成型条件,使得该工艺的气泡形态结构演变与分布发生重大改变。为了研究覆膜与模具型腔内壁差异性成型条件下,该工艺中的气泡形态与分布在长大过程的动态演变及其影响规律,以典型的拉伸试验样条为例,采用数值模拟的方法,通过对比分析不同阶段泡孔长大情况,研究不同阶段的泡孔长大过程,揭示泡孔长大演变规律,为产品泡孔结构的优化调控提供理论基础与方法途径。结果表明,微孔发泡模内表面装饰复合成型工艺的气泡长大演变过程分为不对称熔体流动、充填长大和变形、冷却长大和定型三个阶段;在冷却长大定型阶段,气泡长大发生差异,由于“滞热”现象的存在导致覆膜侧比未覆膜侧气泡大;抑制或者消除气泡在冷却阶段中的长大,对提升微孔发泡模内表面装饰复合成型泡孔质量具有重要意义。

The process of microcellular foaming and in-mold surface decoration combined injection molding was a new process that compounds microcellular foaming injection molding with in-mold surface decoration.Comparing with the conventional microcellular foam injection molding,the bubble morphology structure s evolution and distribution had undergone a significant change due to the embedding of the decorative film.In order to study the dynamic evolution and its influencing laws of the bubble shape and distribution in this process under the differential molding conditions between the decorative film and the mold cavity wall,the process of bubble growth was studied and the evolution law at different stages was revealed by using the simulation methods and comparing and analyzing the bubble growth through,taking a typical tensile test spline as an example.The results show that the bubble growth evolution is divided into three stages,asymmetric melt flow,filling growth and deformation,cooling growth and shaping.The bubbles grow differently from the conventional microcellular foam injection molding in the cooling growth and shaping stage.The bubbles in the decorative film side are larger than those in the non-decorative film side,due to the existence of“heat stagnation”.When bubble growth is suppressed or eliminated during the cooling stage,it has great significance for improving the quality of the final products using the process of microcellular foaming and in-mold surface decoration combined injection molding.