Study of Skin/Core Distribution and Part Mechanical Properties During Microcellular Co-Injection Molding Process Using Gas Counter Pressure

• Main Authors: Wei-Zuo Lin, 林威佐
• Other Authors: Shia-Chung Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/09576133473665309454

碩士 === 中原大學 === 機械工程研究所 === 103 === Microcellular Injection Molding can shorten the molding cycle, save material, reduce the molding pressure, and reduce part shrinkage and warpage. However, flow marks on the part surface cause surface quality issue and reduce the applicability of the products. Microcellular Co-Injection Molding combines the advantages of both microcellular injection molding and co-injection molding. Using non-foaming material as skin layer can improve the surface quality of products, while the core layer material still uses supercritical fluid to form physical foaming bubbles. Therefore, it can produce good-appearance, lightweight, environmentally friendly, and material-and-energy-saving products. This study is about Microcellular Co-Injection Molding, using PP plastic as skin layer material and PP plastic mixed by supercritical nitrogen fluid as the core layer material to make physical foaming inside. The measurements comprised tensile strength, part weight, surface gloss, and skin layer thickness of the products. Then, the Taguchi methods was used to analyze data, identify the effect of molding parameters, and finally find out the robust design parameters for mechanical properties described above. In addition, Gas Counter Pressure (GCP) technology was combined with microcellular co-injection molding to discuss the effect of GCP on the mechanical properties. The results show that microcellular co-injection molding products exhibit the advantages of the non-foaming and foaming plastics. They have excellent surface quality, good tensile strength, and good weight reduction. This can be simply controlled by molding parameters, or it can be further controlled by using GCP technology. Although GCP lowers the part weight reduction, it positively enhances the tensile strength and surface gloss, and it can also be used to change the skin layer thickness.