Effect of non-reactive solvent on the formation and properties of porous epoxy thermosets formed via reaction-induced phase separation

BACKGROUND: A reaction-induced process for producing controlled-porosity epoxy thermosets with the aid of solvents is presented. The curing reactions were carried out in diglycidyl ether of bisphenol A and 4,4'-diaminodicyclohexyl methane systems in the presence of appropriate solvents. RESULTS: The phase separation during the polymerization with appropriate solvent was characterized using dynamic light scattering. Supercritical carbon dioxide was used to extract the solvent from the epoxy resin matrix. The morphology and the porosity within the epoxy thermosets were investigated using scanning electron microscopy and atomic force microscopy as a function of solvent content. The results showed that porous epoxy networks with average pore size ranging from 1 to 20 mu m were obtained, and the size of pores could be varied by changing the solvent content. Thermal properties were investigated using differential scanning calorimetry and thermogravimetric analysis. The introduction of solvent decreased the glass transition temperature and the thermal stability of the epoxy thermosets but showed no influence on the degradation of the main networks. CONCLUSION: Porous epoxy thermosets have been successfully fabricated through a novel reaction-induced phase separation process with the aid of appropriate solvents. They should open a wide range of opportunities for new applications. (C) 2008 Society of Chemical Industry