Flake Orientation in Injection Molding of Pigmented Thermoplastics

Abstract

In the present work, experimental studies are carried out to understand orientation kinematics of pigment flakes during the injection molding process. The injection molding experiments are carried out using ABS resin compounded with aluminum flakes. Thin specimens are sliced off from the injection molded sample, and then the orientation distribution is observed using transmitted microscopy. Generally, the microscopic result shows a sandwich structure where the orientation state near the mid-plane differs significantly from that around the surface. Particularly at the weldline region, locally different orientation is observed near the part surface, which is the result of fountain flow at the melt front. Also the effect of mold temperature on the flake orientation is presented.