Phase separation during the curing reaction in blends of diglycidly ether of bisphenol A

polysulfone and diaminodiphenylsulfone(DDS

curing agent) was studied. Effects of epoxy resins with different molecular weight on phase structure of the blends were investigated. The relation between the degree of conversion and reaction time revealed that vitrification and gelation greatly affected the formation of phase structure in the low molecular weight epxoy systems. When Tg of the epoxy-rich phase went up to the reaction temperature

both reaction and phase separation were suppressed.While in the high molecular weight epoxy systems

the viscosity increasing of epoxy resins played an important role. Although the degree of conversion of the epoxy-rich phase did not reach the gel point after 24h precure

phase separation was suppressed due to the high viscosity of the systems. SEM results showed that the desired phase structure could be achieced by using epoxy resins with different molecular weight.