Engineering analysis of reaction injection molding(RIM) process of epoxy resin

Abstract

An engineering analysis of reaction injection molding (RIM) process of epoxy resin was carried out through numerical simulation with experimental verification. The epoxy system was made from diglycidyl ether of bisphenol A (DGEBA) and triethylenetetramine (TETA). The reaction kinetic equation was determined by a dynamic Differential Scanning Calorimetry (DSC) method and the viscosity change was measured by a Rheometrics Mechanical Spectrometer (RMS). The viscosity model was obtained from the kinetic equation and the empirical viscosity data through a multivariable nonlinear regression. For the simulation, the balance equations for mole, momentum, and energy in cylindrical coordinates were established for a disc type mold. By means of a computer, they were solved simultaneously to calculate the temperature, conversion, viscosity and velocity profiles during filling and curing at various molding conditions. A small scale RIM experiment was carried out to compare the numerical results. It was observed that there was about 10 second lag in reaching maximum exothermic temperature in experimental data, which may be related to incomplete mixing of two reactants. An attempt of the moldability analysis to establish the moldability window and to optimize the process parameters, was made with the criteria of cycle time and maximum exothermic temperature. The moldability window was determined by plotting all the criteria on a single diagram. The major result obtained from this moldability analysis was that the circulating fluid temperature was the most important parameter controlling the process.