Controlled orientation of reflective pigment and optical property characterization of injection‐molded polypropylene

Abstract

Abstract The aims of the research reported were to explore the possibility of removing surface weld lines from highly reflective aluminum pigmented polypropylene injection moldings. Moldings were optically characterized and their characteristics attributed to pigment orientation present in the samples. Conventional injection molding and two novel molding techniques were employed for this investigation, Shear Controlled Orientation Injection Molding (SCORIM) and Bright Surface Molding (BSM). Further, the two techniques, SCORIM and BSM, were used in series and termed SBM to remove surface weld lines. The use of SBM enabled the re‐orientation of the pigment in order to induce a uniform direction for the “flip‐flop” effect where flow fronts have impinged from different directions. These moldings were then quantitatively characterized using a gonio‐spectrophotometer. Their different reflective surface characters were then related to the angle of orientation induced by the respective processing technologies used.