EMULSION STABILITY AND RIGID FOAMS FROM STYRENE OR DIVINYLBENZENE WATER-IN-OIL EMULSIONS

High internal phase emulsions (HIPEs) provide an attractive route to open cell foams. In this paper, we extend our earlier work to include oil phases comprised of 100% styrene or 100% divinylbenzene. In addition, we have evaluated the effects of oil-soluble versus water-soluble polymerization initiators, aqueous-phase salt concentrations, and the degree of cross-linking on the microstructure and compressive properties. Foam cell sizes were found to be inversely related to surfactant level, relatively insensitive to increases in the monomer levels, but greatly affected by salt concentration. The highest salt levels gave the smallest cells. Divinylbenzene gave smaller foam cells than styrene. Only a few percent of divinylbenzene was necessary to obtain near optimum stiffness. Crush strength followed elastic modulus. The best textured foams generally had the best formed cells and the most open microstructure. © 1990, American Chemical Society. All rights reserved.