射出成形品上のフローマーク発現機構の伝熱工学的検討

Abstract

This paper deals with the basic mechanism dominating the wavelike flow mark generation in polymer injection molding. There have been a number of papers describing the relation between molding conditions and flow mark generation in polymer injection moldings, but very limited information about the basic mechanism dominating the flow mark generation has so far been reported. In the present paper, the authors paid attention to the development of the frozen polymer layer adjacent to the mold wall, just behind the melt-mold contact line, so as to evaluate analytically the bending strain in the developing frozen layer due to contraction of the polymer during solidification, and tried to correlate the flow mark generation with the bending strain. The result clearly showed that the aspect ratio of flow marks estimated from the bending strain in the frozen layer agrees well not only with the aspect ratios of the actual flow marks measured by ourselves, but also with the ones reported in the literature. The authors therefore concluded that the basic mechanism dominating the flow mark generation can be attributed to the bending strain in the developing frozen layer due to contraction of polymer during solidification.