Influence of the Mold Temperature and Part Thickness on the Replication Quality and Molecular Orientation in Compression Injection Molding of Polystyrene
Influence of the Mold Temperature and Part Thickness on the Replication Quality and Molecular Orientation in Compression Injection Molding of Polystyrene
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DOI：
10.3139/217.3802
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发表时间：
2019-08-01
影响因子：
1.3
通讯作者：
Drummer, D.
中科院分区：
文献类型：
--
作者：
Roth, B.;Zhou, M-Y;Drummer, D.
众所周知，具有动态模具温度控制的注射成型工艺导致高纵横比微结构的良好复制质量。然而，在保持压力阶段期间的不均匀压力分布导致部件特性的各向异性、低尺寸精度，并且特别是对于光学聚合物，导致不期望的应力双折射。各向异性是基于分子链在流动方向上的取向，其可以通过注射压缩成型（ICM）工艺来减少。为了利用来自两种工艺的协同作用，可以利用具有动态模具温度控制的注射压缩模制工艺。在本次调查的范围内，新的过程中，在升高的模具温度（ICM_EMT）的ICM过程中重现，并与注塑成型（IM）的成型精度和光学性能的依赖组件的厚度和模具温度进行了比较。为了评估成型精度，线侵蚀的腔表面上的微结构的粗糙度进行了测量。为了确定取向度，所考虑的光学性质是透射率和路径差。结果表明，适应ICM过程是能够实现高度的复制精度与低程度的取向，特别是对于薄壁部件。ICM在升高的模具温度下将具有最低壁厚的部件中的路径差减小了两倍，同时优化了微观结构的复制。这也可以通过传输测量来证实。
It is well known that the process of injection molding with dynamic mold temperature control leads to a good replication quality of high aspect ratio microstructures. However, the inhomogeneous pressure distribution during the holding pressure phase results in an anisotropy of the component properties, low dimensional accuracy and, especially with optical polymers, in undesired stress birefringence. The anisotropy is based on the orientation of the molecular chains in the flow direction, which can be reduced by an injection-compression molding (ICM) process. In order to use the synergy from both processes, an injection-compression molding process with dynamic mold temperature control can be utilized. Within the scope of this investigation, the new process was reproduced by an ICM process at elevated mold temperature (ICM_EMT) and compared with injection molding (IM) with regard to molding accuracy and optical properties in dependence of component thickness and mold temperature. In order to evaluate the molding accuracy, the roughness of a wire-eroded microstructure on the cavity surface was measured. To determine the degree of orientation, the optical properties considered were the transmission and the path difference. It was shown that the adapted ICM process was able to achieve a high degree of replication accuracy with a low degree of orientation, especially for thin-walled components. ICM at elevated mold temperature reduced the path difference in the components with the lowest wall thickness by a factor of two while at the same time optimizing the replication of the microstructure. This could also be confirmed by transmission measurements.