Morphology and flow effect of microinjection-molded plastic microgears

Interest in the microinjection molding (μIM) process has grown as the demand for microparts increased for various electronics, transportation, communications, biomedical, and other applications. Recently, we have conducted an intensive research program to understand the details of this process and the material–process–property relationships for various polymers. In the present study, a microgear micropart was presented, in order to investigate the effects of processing conditions on microstructure, mechanical properties, and thermal properties; microtomed and examined using polarized light microscopy; and differential scanning calorimetry for investigation of morphology. Various microstructural features, such as morphological layer thickness and crystalline polymorphs, were observed and analyzed in light of the thermomechanical history. A skin-core region was observed, with spherulites predominating the core region, and highly oriented lamellae appeared in the skin layer. Numerical simulation of filling phase of microgear gives us a detailed description of the thermal history and flow, in which contribute to better understanding on the origin differences in the morphologies among the layers across the part thicknesses in view of the prevailing process conditions. Copyright © 2016 John Wiley & Sons, Ltd.