Three‐dimensional modeling of reaction injection molding. II: Application

Abstract

The objective of this research is to demonstrate the application of a general model of reaction injection molding (RIM) to a complex shaped mold part. Using the fundamental physical and chemical properties of the RIM system, prediction of RIM moldability can be made. The numerical techniques used in this research are presented in a previous paper (1). The rigorous modeling of the transport processes and the dynamics of the filling front for a particular application are described in this work. MTRODUCTIONhe objective of this research is to develop and T apply a tool for the evaluation of flow, temperature. and conversion in thick-walled or complex polymeric part prepared by reaction injection molding (RIM). Essentially, all parts currently produced by the molding of reactive polymers are characterized by thin walls. The Wing of such molds is often essentially two-dimensional. Dicyclopentadiene (DCPD) (2) based systems, however, can be prepared to delay the onset of polymerization. Thus, large complex shaped or thick-walled parts can be filled before gelling. The description of the filling process for purpose of optimization and control requires a model with three-dimensional capability.Because monomers and low-molecular-weight polymers are used as feed materials in RIM, the viscosity of the reactants is low. Because of the low viscosity of the reactants, inertial effects are often significant during filling. This, combined with the rapid and ex@ thermic reaction, results in a very complicated filling behavior. Complex shaped or thick-walled parts may exhibit significant gradients in physical and chemical properties and may be sensitive to the filling dynamics and operating conditions. In addition, trial and error approaches to mold design are not economically viable if several-hundred-pound parts are produced in thick-walled molds. These complications require sophisticated computer-aided tools for process simulation, design, and control. A model developed in our laboratories (1). however, demonstrates the capability for predicting flow, reaction, and heat transfer behavior in a complicated three-dimensional mold. The basic capacity of the model to simulate flow, reaction, and heat transfer phenomena in a large, complex RIM mold and operating condition effects on product properties is demonstrated in this paper.The numerical techniques used in this research include adaptation of the SIMPLE algorithm developed by Patankar (3) for a moving-front, two-phase system with non-negligible inertial effects, and exothermic chemical reaction. The model predictions of temperature compare favorably with available data on simple two-dimensional molds. In a previous paper, the data of Castro and Macosko (4) were used to test the model's ability to predict concentration and temperature in a simple mold. The ability of the model to predict the dynamics of the filling front in more complicated molds was evaluated by comparison to mold filling experiments with water and polyurethane foam (1).In this work, the applicability of the mod...

Numerical simulation of mold filling in foam reaction injection molding

“…For this reason, there have been few studies reported on FRIM. There have been some numerical simulations of the RIM process [10][11][12][13][14]. In these studies, numerical methods similar to those used for injection molding were used to simulate the process.…”

Evaluation of the Heating System From an Injection Molding Machine

“…The pieces obtained from injection are also described by an increased level of smoothing surfaces, as well as an acceptable dimensional precision. As examples of finite parts obtained from an injection process it can be mentioned: lids, cans, cogs, bushings, liners and triangles [1][2][3][4][5].…”

“…The main factors that determine the quality of the finite parts obtained by using different processes and also injection are: the material used (thermoplastic materials, thermorigid and elastomer), the shape of the finite part, parameters of the injection regime (especially the plasticizing temperature of the material, the pressure and speed of injection). Also, the piece quality and performances after production and/or utilization, depend in many cases on the production parameters monitoring and optimization [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”