Gel Prediction of Unsaturated Polyester Resins from a Resin Molecular Aspect

Abstract
The influence of chemical structure of unsaturated polyester (UP) prepoly mer 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, Rc/f, needed to reach gelation state for each studied system is determined and is correlated with Flory interaction parameter, χ. A linear relationship of Rc/f and χ is obtained, which provides an opportunity to predict the gelation of UP resins from a resin molecular aspect.