A study of crosslinking of diglycidylether of bisphenol A (DGEBA) by four copolymers of poly(acrylic acid-co-styrene) having different acid group percentages, in the range 7.6 -76.6%, was done by FTIR. The study was done in the isothermal mode for four different temperatures, the reaction being accelerated by triethylamine. We followed each by temperature and the variation of the area of the epoxy infrared band (912-916 cm Ϫ1 ) versus time. The results showed that the mechanism was complex and depended on the acid composition in the copolymer. Three types of reaction were involved: addition esterification, etherification, and condensation esterification.
ABSTRACT:The effects of temperature, initiator, and accelerator levels on the curing of an epoxy bisphenol-A vinyl ester resin Derakane 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.
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