Noble aluminum-pigmented metallic polymers II: Effects of inorganic filler on weld- and flow-line visibility

Abstract

Aluminum flakes, inorganic filler, and Acrylonitrile–butadiene–styrene (ABS) polymer were mixed to form noble aluminum-pigmented metallic polymers. The effects of inorganic filler on weld- and flow-line visibility were investigated using field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The aluminum flakes were poorly oriented and not uniformly distributed at both hole and gate locations. Addition of inorganic filler improved flake orientation and distribution quality. Traditional flakes have relatively flat surfaces and high surface areas that reflect light in a highly angular manner, which results in a metallic appearance which varies with viewing angle. Comparatively, light reflected from polymers containing both aluminum flakes and specific filler pigments exhibits much less angular dependence, i.e., the flop effect of traditional aluminum pigments is minimized. The loading, size, and shape of the inorganic filler particles affected weld and flow line visibility. Adding a spherical filler with narrow particle size distribution can better stabilize the orientation of aluminum flakes in flow- and weld-line regions compared with irregularly shaped filler particles. The choice of inorganic pigment type and its optimum loading strongly affect the visibility of flow and weld lines.