Experimental assessment and optimization of shrinkage behavior of injection molded polycarbonate parts

Shrinkage is one of the most important defects in polymeric parts. Although there are several studies in order to control and reduce the shrinkage of polymeric parts, there is no systematic investigation on the shrinkage of injection molded polycarbonate (PC) parts. Therefore, the comprehensive investigation of the shrinkage behavior of PC parts was conducted in the present study. Response surface methodology (RSM) was utilized and PC samples were injection molded in different conditions based on the design of experiments. The shrinkage was studied in both longitudinal and latitudinal directions. The measurements were performed at five points in latitudinal and three points in longitudinal. The shrinkage behavior respect to the distance from the gate was studied. A comparative analysis between the shrinkage across and along the injection direction was performed. Analysis of variance tool of RSM method was utilized in order to recognize most effective parameters on the volumetric shrinkage. A regression model was proposed to estimate the volumetric shrinkage of the PC with high accuracy. The interaction effect of parameters on the volumetric shrinkage was analyzed and different solutions to control the shrinkage were recognized.