The phase separation evolution of polyethersulfone/epoxy resin/4,4'-methylene-bis(2,6-
dimethylaniline) blends was investigated by optical microscopy (OM), time resolved light scattering (TRLS) and scanning electron microscopy (SEM). The experimental results indicate that there exists viscoelastic effect on the phase separation evolution. The double phase separation was observed in the blend with lower content of PES (13.2 wt% and 15.9 wt%) cured at 120 and 140 ℃. However, this phenomenon did not occur when the higher PES content blend (18.5 wt%) was cured at the same temperatures.

Key words: double phase separation, viscoelastic, thermoplastic-thermoset blends