| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 99 === Microcellular injection molding (MuCell) offers many advantages such as material and energy saving, melt viscosity and warpage reduction, but the application of Mucell technology is not common due to the defects of surface quality. There are some new ways to improve the surface quality of Mucell molded part in recent years, but the mechanical properties still have not been widely discussed. The purpose of this study is to develop a foaming control by Gas Counter Pressure (GCP) combined with mold temperature control technology during MuCell process and to investigate its relevant influence on mechanical properties.
The results reveal that under GCP control alone, it can effectively influence the foam qualities and the thickness of Frozen layer, also increase the tensile strength but decrease the Impact strength; the lower the mold temperature control for the frozen layer, the more obvious bubble size increase; the greater the average bubble size, the lower the tensile strength is, and the impact strength does not increase until the average bubble size increase to 30μm ~80μm. The impact strength will decrease while average bubble size is bigger than 80μm.Using both GCP and dynamic mold temperature control, the thickness of the frozen layer is thinner than using GCP only, and the average bubble size is smaller and more uniform than using dynamic mold temperature control only. In this case both tensile strength and impact strength has a better performance. For tensile strength, the numbers of controlled bubbles would be 10% more than only using dynamic mold temperature control in the same mold temperature; for the impact strength, in the same parameters and the uniform bubble size GCP, the mold temperature can improve the thin solidified layer, which can improve the impact strength.
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