Predicting the phase behaviour of solvent-modified epoxy resins

The Flory-Huggins equation has been used to model the equilibrium phase beh aviour of a solvent-modified epoxy resin intended for the fabrication of po rous components by chemically induced phase separation followed by evacuati on of the solvent after curing. Points in composition-temperature space cor responding to a transition from homogeneous to heterogeneous postcuring mic rostructures have been identified for a variety of solvents using a thermal gradient oven. Assuming this transition to coincide with the cloud-point c urve corresponding to the gel point of the resin, the data were used in con junction with the predictions of the Flory-Huggins equation to estimate the interaction parameter and its temperature dependence for each solvent. Pha se diagrams in composition-conversion space were then calculated for a rang e of curing temperatures.