GEL PREDICTION OF UNSATURATED POLYESTER RESINS FROM A RESIN MOLECULAR ASPECT

The influence of chemical structure of unsaturated polyester (UP) prepolymer on gelation of UP resins is studied by varying NPG content in the UP prepolymer backbone. Also, the effects of styrene concentration and solvent quality on gelation are evaluated. A corrected gelation model concerning free radical ionization reaction based on a microgel mechanism is proposed. The critical free radical concentration, R(c)/(f), needed to reach gelation state for each studied system is determined and is correlated with Flory interaction parameter, chi. A linear relationship of R(c)/f and chi is obtained, which provides an opportunity to predict the gelation of UP resins from a resin molecular aspect.