CHEMICALLY-INDUCED PHASE-SEPARATION - A NEW TECHNIQUE FOR THE SYNTHESIS OF MACROPOROUS EPOXY NETWORKS

We have developed a new technology, based on chemically induced phase separation, that allows for the synthesis of porous epoxies with a clo sed cell morphology and a narrow pore size distribution in the microme tre range. The potential of this technique for the synthesis of new ty pes of porous thermosets is enlightened by the comparison with the cur rent state of the art on technologies for the preparation of macroporo us polymeric materials. The strategy of the chemically induced phase s eparation technique, as a general approach for the synthesis of macrop orous thermosets with controlled morphology is presented. The particul ar system reported is a diglycidylether of bisphenol-A cured with 2,2' -bis(4-amino-cyclohexyl)-propane in the presence of hexane or cyclohex ane. Depending on the hexane concentration, the morphology can be vari ed ranging from a monomodal to bimodal distribution. By regarding the kinetics and the development of a bimodal distribution, we surmise tha t the phase separation proceeds via a nucleation and growth mechanism. The influence of internal and external reaction parameters, such as c hemical nature of the solvent, solvent concentration and curing temper ature on the final morphology are reported. These porous materials are characterized by a significantly lower density without any loss in th ermal stability compared to the neat matrix. Copyright (C) 1996 Elsevi er Science Ltd.