MODELING THE DIELECTRIC RESPONSE OF UNSATURATED POLYESTER RESIN DURING CURE

The dielectric relaxation of unsaturated polyester resin during cure w as modeled using a modified Williams-Watts decay function. The dielect ric response was studied using dielectric measurements coupled with tw o dynamic mechanical measurement methods. It was found that the variat ion of the relaxation time during cure is a WLF process using T-g(alph a) (alpha-conversion) as the varied temperature. It was shown that thi s process fits the Williams-Watts decay function Phi(t) = exp(-(t/tau) (beta)) where tau-relaxation time and beta-empirical parameter are tim e dependent. It was found that tau obeys a time dependent power law ru le and beta depends linearly on log(time). Using this modified decay f unction, it was shown that the experimental dielectric response measur ed during cure agrees well with the computed response. Relaxation time s above and below the dielectric measurement system capability were co mputed thus, demonstrating the capability of yielding the entire relax ation times spectrum during cure, out of a single limited frequency di electric measurement