THE EFFECT OF CURE CYCLE OF UNSATURATED POLYESTER RESIN ON THE TEMPERATURE AND CONVERSION PROFILES

Temperature and conversion profiles during hot curing of an unsaturate d polyester resin were studied. It was found, unexpectedly, that the r eaction exotherm was largest in the outer layer close to the hot mold surface and least in the center core. The opposite was true for room t emperature curing with a different initiator system. Comparison of the experimental results with heat transfer calculations has led to the c onclusion that the kinetic character of cure across the polyester slab thickness was location-dependent. The variation with location was int erpreted in terms of diffusion of the initiator components from the co re towards the surface owing to their faster depletion close to the ho t surface and the imposition of a temperature profile. Simulation of t he experimental results was possible by combining the heat transfer eq uation with a kinetic equation accounting for an inhibitor induction t ime and a modified Arrhenius equation containing a location-dependent activation energy.