SOME EFFECTS OF STRUCTURE ON THE CURE OF GLYCIDYLETHER EPOXY-RESINS

Three glycidylether epoxy resins with functionalities of 2, 3 and 4 were purified and extensively characterized. The cure of the resins with diaminodiphenylsulphone, both alone and as blends, was studied using rheometry and differential scanning calorimetry. The effect of resin functionality on the rate of cure was greater than would be expected from simple concentration effects. The kinetics were best described by an autocatalytic model over approximately the first 40% of reaction. Thereafter an nth order expression gave a better fit to the data. The modulus crossover point, t(G') = G", was found to be a reproducible indication of gelation, and the fractional conversions at this point, obtained by combining d.s.c. and rheology data, were compared to the values predicted by gelation theory. A model was used to predict the viscosity of samples during cure as an aid to processing.