GOALI: Development of Advanced Molding Technology for Polymer Micro-/Nano-Fabrication

本研究项目旨在研究基于热塑性聚合物的成型技术，即高速/高压（薄壁）注塑成型和微压花，因为它们具有低成本大规模生产的巨大潜力。 在高速/高压（薄壁）注射成型中，聚合物熔体可以在两倍于常规注射成型的压力下流动，并且剪切速率可以高出10倍以上。 目前的商业模拟代码，通常用于评估成型性和周期时间不准确预测模具填充在这些极高的压力和剪切速率。 将创建聚碳酸酯的高剪切速率和高压流变学的实验数据库，并将其用作商业软件C-MOLD的输入。 还将详细研究高剪切应力对模具磨损和“模制”应力的影响。C-MOLD将用于模拟微尺度特征的成型。 该模拟软件能够预测流动模式，压力和模具表面上的剪切应力。 在微压花中，计划是围绕选定的聚合物的玻璃化转变温度进行详细的热流变学研究。模塑周期将根据聚合物的流变行为设计，而不是任意选择模塑温度。 热流变学结果也将用于FEM模拟，以计算模具和模塑聚合物产品中的应力分布。 微米级模具特征上的预测剪切应力将与实验观察到的模具磨损水平和“模制”应力相关。模拟和实验结果（压力，温度，剪切应力，填充时间和冷却时间）也将用于设计工艺窗口作为特征尺寸/纵横比，模具材料和加工条件的函数。 其目标是开发一种有效的大规模生产方法，其周期时间与传统的注塑成型和压花相似或更短。

This Grant Opportunities for Academic Liaison with Industry (GOALI) research project is to investigate thermoplastic polymer-based molding technologies, i.e. high speed/ high pressure (thin wall) injection molding, and micro-embossing, because of their great potential for low cost mass production. In high speed/high pressure (thin wall) injection molding, the polymer melt may flow under a pressure twice as much as in conventional injection molding, and the shear rate can be more than 10 times higher. Current commercial simulation codes which are typically used to evaluate moldability and cycle time do not accurately predict mold filling at these extremely high pressures and shear rates. An experimental data base of the high shear rate and high pressure rheology of polycarbonate will be created and used as input in a commercial software called C-MOLD. The effect of high shear stresses on mold wear and 'molded-in' stresses will also be investigated in detail. C-MOLD will be used to simulate the molding of micro-scale features. The simulation software is capable of predicting flow patterns, pressures and shear stresses on the mold surface. In micro-embossing, the plan is to carry out detailed thermorheological study around the glass transition temperature of selected polymers. The molding cycle will be designed according to the rheological behavior of polymers, instead of arbitrarily chosen molding temperatures. The thermorheology results will also be used in FEM simulation to calculate the stress distribution in the mold and in the molded polymer product. Predicted shear stresses on the micron scale mold features will be correlated with the experimentally observed level of mold wear and 'molded in' stresses. The simulations and experimental results (pressures, temperatures, shear stresses, fill time, and cooling time) will also be used to design a process window as a function of feature size/aspect ratio, mold material, and processing conditions. The goal is to develop an efficient mass production method with cycle time similar to or less than that in conventional injection molding and embossing.