Micro-Features Formation in Injection Compression Molding

Thin-wall injection molded products with micro-scale surface features of polycarbonate (PC) were produced using precision injection compression molding (ICM) to analyze effects of molding conditions on replication of surface patterns and higher-order structural development of products. The molded parts' flow length using ICM was greater than using injection molding. The compression delay time in ICM, the start time after molten resin injection, was the most important factor for improving flow lengths. Residual strain inside the parts was influenced by compression conditions: it increased concomitantly with increased compression delay time. Compression conditions also influenced optical retardation. Particularly, retardation was decreased at longer delay times because molded parts started solidification inside the cavity at this condition. The replication ratio was higher than by injection molding. Compression conditions influenced the ratio, which decreased drastically at longer delay times. The replication ratio near the flow end was lower than at any other position. The ratio was especially lower for the surface pattern with the high aspect ratio of 2.