2019 年 85 巻 1 号 p. 79-83
In polymer injection molding, to achieve surface appearance resembling metallic coating without painting the molded product, bright material such as aluminum flake is sometimes mixed into the resin. In such cases, the generation of weld lines which appear as lines with different gloss and coloring are formed at the flow front meeting area of molded products and the vicinity areas. In this study, we used an electromagnetically induced heating and cooling injection mold equipped with system to control the melt flow to mold polypropylene containing aluminum flakes. As a result, it was clarified that weld lines with inconsistent coloring can be reduced by controlling the melt flow while heating the mold, and that the preventive effect of the above weld lines improves by a rise of the heating temperature of the cavity wall, advance at the timing of melt flow control starting and increase of a bright flake diameter.