Effects of Thermal Molding Conditions on the Residual Stress and Residual Birefringence in an Injection-Molded Polymer Strip.

Abstract

In this paper, we report a numerical study concerning the effects of thermal molding conditions on the residual stress and birefringence developments frozen in an injection-molded polymer strip. In our numerical calculation, the residual stress frozen in the injection-molded polymer was considered in terms of flow-induced shear stress and cooling-induced thermal stress. Profiles of the residual birefringence were obtained from these stresses using the rheooptical law. The numerical results showed that the residual stress frozen into the injection-molded polymer strip is mainly affected by the cooling rate of the strip while the residual birefringence is dominated by the temperature and velocity of the injected polymer melt. This indicates that the residual stress and residual birefringence can be reduced by controlling the heat transfer during the filling and cooling stages, respectively.