Characteristics of the Skin Layers of Microcellular Injection Molded Parts

• Published in: Polymer-plastics technology and engineering 2006-06, Vol.45 (7), p.871-877
• Main Authors: Lee, Jung Joo, Cha, Sung Woon
• Format: Article
• Language: English
• Subjects: Applied sciences; Cellular; Exact sciences and technology; Forms of application and semi-finished materials; Injection flow rate; Injection velocity; Microcellular injection molding; Polymer industry, paints, wood; Skin layer thickness; Technology of polymers; Temperature gradient; Viscosity
• ISSN: 0360-2559; 1525-6111
• DOI: 10.1080/03602550600611768

The cross-section of products made with the microcellular injection molding process shows the skin layer and the core region where the formation of pores takes place. The cell size, cell density, and cell morphology were found to depend on pressure drop rate, viscosity, cell growth period, and cell coalescence. However, research on the actual mechanisms of the skin layer is rare. Cell morphology and skin layer are of importance as a factor influencing the density and strength of microcellular injection molded parts. Especially, as size of the injection molded parts becomes large, the skin layer size changes, resulting in variation of the foaming rate. Therefore, there is the need to study factors that influence the formation of the skin layer and its thickness. This research proposes a hypothesis on the mechanism of the skin layer formation in microcellular injection molding process and addresses factors influencing skin layer thickness. In addition, the experimental design method was utilized to identify the factors, and the variation in physical properties with skin layer thickness was reported.