Molecular orientation in injection molding: experiments and analysis
Molecular orientation in injection molding: experiments and analysis
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DOI：
10.1007/s00397-003-0325-8
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发表时间：
2004-03-01
期刊：
影响因子：
2.3
通讯作者：
Titomanlio, G
中科院分区：
文献类型：
--
作者：
Pantani, R;Sorrentino, A;Titomanlio, G
在过去的十年中，热塑性聚合物注射成型过程的建模和仿真得到了显着的改善。目前最具挑战性的科学目标之一是可靠地预测成型过程的分子取向模拟。事实上，虽然压力和速度分布可以令人满意地描述粘性模型，聚合物的粘弹性性质需要考虑在分子取向演变的描述。在这项工作中，一个非晶PS注射成型到一个线浇口矩形腔。模塑测试经过仔细表征，并提供进一步分析所需的所有信息。模具包含特殊的模具，可以接受各种大小的门。特别地，使用两个浇口，其厚度分别为1.5mm和0.5mm。通过使用楔形法在模制品中的不同位置和浇口内测量沿着厚度方向的双折射率分布（对于PS，其基本上是取向分布）。通过测量沿流路沿着不同位置处的热收缩来收集关于冻结分子应变量的数据。通过萨莱诺大学开发的软件模拟模塑试验，并使用简单的粘弹性模型来描述由于使用粘性方法获得的运动学效应而引起的分子取向的演变。模拟结果描述了从模塑样品收集的实验数据的主要特征;特别是，填充流的效果在数据和模拟中都是清楚的。此外，还讨论了压力对弛豫时间影响的重要性。
Modeling and simulation of the injection molding process of thermoplastic polymers has remarkably improved over the last decade. One of the most challenging scientific objectives is currently the reliable prediction of molecular orientation simulations of the molding process. Indeed, although pressure and velocity distribution can be satisfactorily described by viscous models, the viscoelastic nature of the polymer needs to be accounted for in the description of molecular orientation evolution. In this work, an amorphous PS was injection molded into a line gate rectangular cavity. Molding tests are carefully characterized and all information needed for further analysis is provided. The molds contained special dies that could accept various sized gates. In particular two gates were used whose thicknesses were 1.5 mm and 0.5 mm, respectively. Birefringence distribution (which for PS is essentially the orientation distribution) along the thickness direction was measured by using the wedge method at different positions in the moldings, and inside the gates. Data regarding the amount of frozen-in molecular strain were gathered by measuring the thermal shrinkage at different positions along the flowpath. Molding tests were simulated by means of a software developed at the University of Salerno, and a simple viscoelastic model was used to describe the evolution of molecular orientation due to the effect of kinematics obtained using a viscous approach. Simulation results describe the main features of experimental data collected from the molded samples; in particular, the effect of the packing flow is clear in both the data and simulations. In addition, the importance of the effect of pressure on relaxation time is discussed.