Abstract: A process for producing an unsaturated resin solution suitable for reaction with a catalyst, water, and a gas releasing salt and a gas-release control agent to produce plastic foam material includes providing an initial unsaturated resin solution with a predetermined relatively low acid value, and mixing the initial unsaturated resin solution with a half-ester to raise the acid value to a predetermined higher value.

Abstract: A process for the production of plastic foam material includes forming a liquid mixture by mixing an unsaturated resin, a catalyst operable to cause curing of the unsaturated resin, a promoter operable to activate the catalyst, a gas-releasing salt, and an acid operable to cause the release of gas from the salt so that the liquid mixture foams and cures by gelling and subsequent hardening. Included in the mixture is a volatile liquid gas-release control agent which volatilizes during curing to maintain gas release passages open in the foam and thereby permit release of gases from the foam during hardening after gellation at least until the foam is structurally stable.