(A) study on the reaction injection molding process and the phase separation behavior of epoxy resin

Abstract

An engineering analysis of the reaction injection molding process of epoxy resin was carried out through model simulations and actual experiments. The vitrification effect during the epoxy curing reaction was studied by the differential scanning calorimetry, and a reaction kinetic equation was derived to describe the effect of the vitrification on the reaction rate at both glassy and rubbery state. The viscosity function was expressed as a function of temperature and conversion and was based on the actual data measured by Rhemetrics Mechanical Spectrometer. The heat capacity and the thermal conductivity were measured by the thermal analyzer. In order to simulate the epoxy RIM Process, balance equations calculating the temperature and conversion change in a disc type mold were established. These equations were solved numerically by a explicit finite difference method with the aid of a computer. The simulation model was verified by comparing the simulated temperature and conversion change with the measured temperature rise and the conversion profile estimated from the glass transition temperature(Tg) profile in the actual RIM experiment. The vitrification occurred during the epoxy RIM process reduced the reaction rate as the Tg of the reacting mixture exceeds or approaches the local reaction temperature inside the mold cacity. The effect was shown as the distribution of the Tg across the thickness direction of the molded product. As an attempt to optimize the RIM process using the simulation model, the effects of the molding parameters such as the feed temperature and the wall temperature on the eject time and the allowable maximum temperature and the viscosity limit for the mixing were analyzed. In order to improve the mechanical properties of the cured epoxy resin, the liquid rubber(CTBN) was added and the phase separation behavior during the reaction was analyzed by the light scattering experiment. The transmitted light intensity was measured and it showed the...