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The V‐notch at weld lines in polystyrene injection moldings
Author(s) -
Tomari K.,
Tonogai S.,
Harada T.,
Hamada H.,
Lee K.,
Morii T.,
Maekawa Z.
Publication year - 1990
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760301508
Subject(s) - materials science , welding , molding (decorative) , composite material , weld line , ultimate tensile strength , polystyrene , groove (engineering) , metallurgy , polymer
A major factor that weakens the weld line in injection moldings is the V‐notch structure. Though the existence of a V‐notch is well known, its depth variation with molding conditions has not been detailed. The aim of this paper is to clarify the V‐notch structure and its effect on the strength of general purpose polystyrene injection moldings. A dog bone type tensile specimen with a weld line was molded under several molding conditions. The surface of the weld line was partially eliminated by cutting with a milling machine to seven levels of cut depth ( D c ). As a result, the weld strength increased with D c to about 50%. The relationship between the weld strength and D c made it possible to determine the V‐notch depth, which vas defined as the “depth of the weld line.” From these results, a hypothesis is proposed that the V‐notch has a structure with a fine groove on the surface and a poorly bonded inner layer. This study considered the relationships among the weld strength, the depth of the weld line, and molding conditions.