CURING REACTION OF SATURATED ALIPHATIC POLYESTER MODIFIED UNSATURATEDPOLYESTER RESINS

Two series of unsaturated polyesters (UPE from isophthalic acid, fumar ic acid, and propylene glycol) were prepared. In series-A resins, UPEs were thickened with isocyanate-terminated saturated aliphatic polyest ers, i.e., an isocyanate-terminated polycaprolactone diol (PE-di-OL), through reaction of the isocyanate group with the hydroxyl group of th e UPE. In series-B resins, the UPEs were mixed with saturated aliphati c polyesters i.e., PE-di-OL. The curing reaction of these two series o f UPEs with styrene was studied by using differential scanning calorim etry (DSC) and gel permeation chromatography (GPC). The DSC data show that for a fixed PE-di-OL molecular weight, the curing reaction rate o f series-A UPE is faster than that of series-B UPE. The variation of m icrogel size during curing was studied by GPC. These results revealed that microgel formation has a great effect on the kinetics of cure for the unsaturated polyester-styrene system. The curing of these two ser ies of UPEs is found to strongly depend on the compatibility of the co mponents in the curing system.