Interface development and encapsulation in simultaneous coinjection molding. I. Two‐dimensional modeling and formulation

Abstract

ABSTRACT:In the coinjection-molding process two polymers are injected into a mold sequentially or simultaneously. During the process one polymer melt forms the skin and the other forms the core, resulting in an encapsulated sandwich structure. In an attempt to develop a process model and simulation of simultaneous coinjection molding, along with the interface treatment a theoretical approach, physical model, and numerical algorithm were formulated based on the Hele-Shaw approximation. A detailed picture of the dynamics and kinematics of the interface evolution, providing a description of the multilayer flow and interface development during the multicomponent injection-molding process, information typically lacking in the available literature, is systematically presented. Based on the developed numerical simulation code, the moldability of various material combinations can be evaluated, which is required for process optimization.

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

“…Table 4 shows the comparison of zero shear viscosity at different temperatures which were calculated from the modified four-parameter Cross model by Li et al [22] and the WLF model in this work. From Table 4, it can be seen that the values of zero shear viscosity at different temperatures in this work are consistent with the results of the modified four-parameter Cross model.…”

“…Li et al [22,23] presented a 2D simulation of simultaneous CIM along with the interface treatment. The theoretical approach, physical model and numerical algorithm were based on the Hele-Shaw approximation.…”

“…To date, several full 3D simulation approaches for injection molding have been developed, but only a few studies were devoted to the CIM. Most studies concerning CIM were based on the Hele-Shaw approximation (2.5D), except those by Ilinca et al [2] and Ilinca and Hétu [15][16][17], who used a 3D solution algorithm to predict the interface evolution between skin and core materials during filling for the sequential CIM, while a few of them considered the simultaneous CIM [20][21][22][23]. Ilinca et al [2] developed a finite element flow analysis algorithm to simulate the sequential CIM process; two additional transport equations were introduced to track the air/skin and skin/core polymer interfaces by the pseudo-concentration method.…”

Effects of Process Parameters on the Skin/Core Distribution in Co-Injection: Experiments and Simulations Using a Simple Geometry

“…A less expensive approach to the design of an effective co-injection process is provided by computer simulations, and therefore some research work was carried out in this direction [13][14][15][16] . Much of the work was devoted to the development of finite volume [13][14][15] or finite element [16] schemes to describe the two phase flow both in sequential and simultaneous co-injection processes, and to determine the final core=skin structure in the part.…”

“…Much of the work was devoted to the development of finite volume [13][14][15] or finite element [16] schemes to describe the two phase flow both in sequential and simultaneous co-injection processes, and to determine the final core=skin structure in the part. Some recent contributions check the potential of commercially available simulation packages, such as Moldflow or C-Mold, in determining the flow behaviour during co-injection moulding [17,18] .…”