Effects of processing conditions on the curing of a vinyl ester resin

The effects of temperature, initiator, and accelerator levels on the curing of an epoxy bisphenol-A vinyl ester resin Derakane(R) 411-45 (formulated with styrene) were investigated by gel-time and exotherm-peak measurements on bulk samples. It was observed that the gel time was reduced as the initiator or accelerator ratio increased. Except at higher contents of the accelerator, a small kinetic plateau was seen in the gel curve and a shift of the maximum exotherm toward high temperatures in the DSC curves. This was explained by the dual role played by the accelerator species. A regression analysis of all gel-time data showed a dependence of 3/2 order in the accelerator and first order in the initiator concentrations. Thus, for this polymerization initiation system, the gel time can be predicted for any initiator and cobalt levels and at any temperature within the ranges studied. The effect of the initiator on the unreacted styrene and vinyl ester was also examined. (C) 2002 Wiley Periodicals, Inc.