Cure behavior, thermal stability and flexural properties of unsaturated polyester/vinyl ester blends

The effects of catalyst, accelerator and blend composition on the cure behavior of unsaturated polyester resin (UPE), vinyl ester resin (VE) and their blends were studied using differential scanning calorimetry (DSC). The DSC thermograms strongly depend on each variable. The result shows that the small exothermic peak at 115 degreesC is due mainly to the UPE component in the UPE/VE blends and the large one at 134 similar to 138 degreesC is due mainly to the VE component. The results also indicate that the change of the DSC thermogram measured after each blend was exposed to high temperature 180 degreesC and the fast curing conditions of a few tens seconds provide useful information on understanding the thermal processing of a blend at high speed. The measurements of resin flow time represent that there are three distinct stages of cure in the UPENE blends: induction, transition and macro-gelation stages, as similarly reported for UPE by others earlier. The thermal stability and flexural properties of the cured UPE are significantly improved by blending it with the VE, depending on the composition.