Birefringence and interface in sequential co‐injection molding of amorphous polymers: Simulation and experiment

Abstract

Modelings of the interface distribution and flow-induced residual stresses and birefringence in the sequential coinjection molding (CIM) of a center-gated disk were carried out using a numerical scheme based on a hybrid finite element/finite difference/control volume method. A nonlinear viscoelastic constitutive equation and stressoptical rule were used to model the frozen-in flow stresses in disks. The compressibility of melts is included in modeling of the packing and cooling stages and not in the filling stage. The thermally induced residual birefringence was calculated using the linear viscoelastic and photoviscoelastic constitutive equations combined with the first-order rate equation for volume relaxation and the master curves for the relaxation modulus and strainoptical coefficient functions of each polymer. The influence of the processing variables including melt and mold temperatures and volume of skin melt on the birefringence and interface distribution was analyzed for multilayered PS-PC-PS, PS-PMMA-PS, and PMMA-PC-PMMA molded disks obtained by CIM. The interface distribution and residual birefringence in the molded disks were measured. The measured interface distributions and the gapwise birefringence distributions in CIM disks were found to be in a fair agreement with the predicted interface distributions and the total residual birefringence obtained by the summation of the predicted frozen-in flow and thermal birefringence. POLYM. ENG. SCI., 55:88-106, 2015.

Visualization and simulation of filling process of simultaneous co-injection molding based on level set method

“…However, the numerical results are obtained from several discrete points based on 2D simulation and were not shown as a continuous molding process. The elasticity of polymer melt was not considered in most of the related studies of CIM, with the exception of studies by Kim and Isayev [19]. Kim and Isayev [19] described a 2D viscoelastic simulation of the flow and thermal birefringence development in the filling, packing and cooling stages of the sequential CIM.…”

New boundary conditions for simulating the filling stage of the injection molding process

“…A large number of works are currently being published on the subject of numerical simulation of the injection molding process, considering new and different phenomena that may occur along the process, and also taking into account the rheology of the different fluids. For instance, the study of Azaman et al (2013) on residual stress distribution in the injection molding process using wood polymer composites and the study of Kim and Isayev (2015) in birefringence using co-injection molding.…”

Nondestructive measurement of layer thickness in water‐assisted coinjection‐molded product by ultrasonic technology

“…Water‐assisted coinjection molding (WACIM) is an innovative polymer injection‐molding technology, which is used to produce hollow products with multilayer walls . Comparable to water‐assisted injection molding (WAIM) and coinjection molding (CIM), WACIM has advantages of reduction of amount of polymer used, weight reduction, performance improvement, and greater freedom of product design . Recently, WACIM technology has been widely used for automotive components, household items, and furniture parts, highlighting a bright future for WACIM with regard to market prospects .…”