Pheology and Heat Transfer Control of Microscale Instability Phenomena on Injection Molded Polymer Surfaces

现有的流痕生成假说的广泛变化和仍然是推测性的，表明对生成机制还没有明确的理解。基于文献研究的结果。提出了两个主要的研究问题：（1）提供流痕生成的描述：波状流痕在哪里以及如何生成？(2)对流痕的产生提供解释：对产生波状流痕的机制提出假设。进行实验以获得以下信息：（1）确定流痕的产生点，即，在熔体和模具之间的接触线之前、之后或处，以及（2）观察实际生成过程。这是使用一个注塑机完成的，该注塑机配备了一个专门设计的带有观察窗的模具。(3)成型后的微观表面轮廓分析也在实验研究中发挥了重要作用。特别注意的是热边界条件对流动痕迹的微观几何形状的影响。分析和数值方法被用来模拟在流动前沿和接触线区域的传热。发展了用于解释流痕产生机理的唯象模型和数学模型。该模型是基于假定的热变形的凝固层在该地区的接触线后面。该数学模型可以与实验数据在广泛的操作条件和三种不同的材料。主要结论是：接触线后凝固层的不均匀热收缩是波浪形流痕产生的主要原因。

The widely varying and still speculative nature of existing flow mark generation hypotheses indicated that there was no clear understanding of the generating mechanism yet. Based on the results of the literature study. two main research questions were formulated : (1) Provide a description of flow mark generation : Where, and how do wavelike flow marks generate? (2) Provide an explanation for flow mark generation : Construct an hypothesis for the mechanism by which wavelike flow marks are caused. Experiments were done to obtain the following information : (1) determination of the point of generation of flow marks, i.e., before, after, or at the contact line between the melt and the mold, and (2), observation of the actual generation process. This was accomplished using an injection molder equipped with a specially designed mold with an observation window. (3) Microscopic surface profile analysis after molding also played an important part in the experimental investigation. Specific attention was given to the effect of the thermal boundary conditions on the micro-geometry of flow marks. Analytical and numerical methods were used to model the heat transfer in the flow front and contact line areas. Phenomenological and mathematical models for explaining the flow mark generation mechanism were developed. The models are based on presumed thermal deformation of the solidifying layer in the area immediately behind the contact line. The mathematical model could be correlated with experimental data over a wide range of operating conditions and for three different materials. The main conclusion is that non- uniform thermal contraction in the solidifying layer behind the contact line appears to be the dominating factor in the mechanism by which wavelike flow marks generate.