On-line tracking of reaction-induced phase separation has been realized for the first time by using high frequency ultrasonic wave

which is based on the Rayleigh scattering of ultrasonic wave on the interface of a multiphasic system.The new technology was employed to track the curing reaction of epoxy resin in PEG medium.The investigation involved the effects of concentration

reaction medium

amount of curing agent and temperature on the reaction-induced phase separation.Based on an intensive analysis of spinodal demixing (SD) in this curing system

a physical model has been put forward

in which two processes have been abstracted to describe the reaction-induced phase separation.One is the process of phase separation

and the other is phase isolation.In the related mathematical model the scattering intensity of ultrasonic wave is expressed as a function of the rates of both phase separation and phase isolation

by which the experimental data from ultasonic tracking have been explained reasonably.The online tracking technology found that under high concentration or by raising the reaction temperature the phase separation would be suppressed by polymerization to yield phase structures with high connectivity.In PEG2000 medium and under high concentration a hysteresis effect of function l（t） was found and the SD mechanism was supported.The phase separation is also influenced by the weight ratio of epoxy resin and curing agent

a ratio of 4/1 was proved to suitable for the completion of both phase separation and polymerization.The new technology made it possible to realize a realtime analysis of the changing of multiphasic structure during the phase separation

which might provide an experimental basis for the control of phase separation.