Abstract
Rheological behavior of thermoset/thermoplastic blends of epoxy/polyethersulphone (PES) was monitored during curing of the epoxy resin. During the isothermal curing of the mixture, a fluctuation in viscosity just before the abrupt viscosity increase was observed. This fluctuation is found to be due to the phase separation of PES from the matrix epoxy resin during the curing. The experimentally observed viscosity fluctuation is simulated with a simple two phase suspension model in terms of the increase in domain size. The viscosity profiles obtained experimentally at different isothermal curing temperatures are in good agreement with the predictions from the simple model taking into account the viscosity change due to the growth of PES domain and the network formation of the epoxy matrix.