Liparoti Sara, Speranza Vito, Pantani Roberto, Titomanlio Giuseppe
Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, SA, Italy.
Institute of Polymers, Composites and Biomaterials (IPCB), The National Research Council, Via Previati 1/C, 23900 Lecco, LC, Italy.
Polymers (Basel). 2021 Sep 24;13(19):3236. doi: 10.3390/polym13193236.
The possibility of tailoring key surface properties through the injection molding process makes it intriguing from the perspective of sustainability enhancement. The surface properties depend on the replication accuracy of micro and nanostructures on moldings; such an accuracy is enhanced with cavity temperature. The simulation of the injection molding process is very challenging in the presence of micro and nanostructures on the cavity surface; this does not allow for the neglect of phenomena generally considered not to influence the overall process. In this paper, a multiscale approach was proposed: in the first step, the simulation of the overall process was conducted without considering the presence of the microstructure; in the second step the outputs of the first step were used as an input to simulate the replication of the microfeature. To this purpose, a lubrication approximation was adopted, and the contribution of the trapped air, which slows down the polymer advancement, was accounted for. A modification of the viscosity equation was also proposed to describe the rheological behavior of isotactic polypropylene at very low temperatures. Concerning the microcavity filling simulation, the modification of the viscosity description at low temperatures consistently describes the process, in terms of polymer solidification. Concerning the replication accuracy, it increases with the cavity surface temperature, consistently with the experimental observations.
通过注塑工艺调整关键表面性能的可能性，从增强可持续性的角度来看很有吸引力。表面性能取决于成型品上微观和纳米结构的复制精度；这种精度会随着模腔温度的升高而提高。在模腔表面存在微观和纳米结构的情况下，注塑工艺的模拟极具挑战性；这使得通常被认为不会影响整个过程的现象不能被忽视。本文提出了一种多尺度方法：第一步，在不考虑微观结构存在的情况下对整个过程进行模拟；第二步，将第一步的输出结果作为输入，模拟微观特征的复制。为此，采用了润滑近似法，并考虑了阻碍聚合物前进的 trapped air 的影响。还提出了粘度方程的修正形式，以描述等规聚丙烯在极低温度下的流变行为。关于微腔填充模拟，低温下粘度描述的修正能够在聚合物固化方面一致地描述该过程。关于复制精度，它随着模腔表面温度的升高而增加，这与实验观察结果一致。
