Abstract: A spray method for making cured polyester resin foam is provided using a liquid unsaturated polyester resin, a sulfonyl hydrazide, an effective amount of a promoter, an effective amountof a catalyst and 0.005-3 parts quaternary ammonium salt.

Abstract: A foamable and simultaneously curable polyester composition is provided. The composition consists essentially of the following (all being in parts by weight):(a) 100 parts liquid unsaturated polyester resin,(b) 0.5 to 10 parts monosubstituted sulfonyl hydrazide having the formula RSO.sub.2 NHNH.sub.2, wherein R is C.sub.1 -C.sub.12 alkyl, C.sub.5 -C.sub.6 cycloalkyl, C.sub.7 -C.sub.10 aralkyl, phenyl, naphthyl, or phenyl substituted with halogen, C.sub.1 -C.sub.12 alkyl or C.sub.1 -C.sub.12 alkoxy,(c) 0.1 to 5.0 parts of a promoter, said promoter consisting essentially of a mixture of organic heavy metal salt and organic alkali metal salt, wherein the heavy metal/alkali metal molar ratio is from 10/1 to 1/10.(d) 0 to 2 parts surfactant,(e) 0 to 250 parts of filler, and(f) 0.3 to 5 parts of a cross-linking initiating compound selected from organic peroxides and organic hydroperoxide.

Abstract: Polyester resin is expanded and cured using mono-substituted sulfonyl hydrozide blowing agent, organic peroxide curative and certain metal promoters.