4 epoxy 6 methylcyclohexylmethyl adipate union carbide erl 4289 and bis 3 4 epoxycyclohexylmethyl adipate union carbide erl 4299 suitable commercially available diglycidyl ethers of bisphenol a are ciba geigy araldite 6010 dow chemical der 331 and shell chemical epon 828 and 826 a polyepoxidized phenol formaldehyde novolak prepolymer is available from dow chemical den 431 and 438 and a polyepoxidized cresol formaldehyde novolak prepolymer is available from ciba geigy araldite 538 a polyglycidyl ether of a polyhydric alcohol is available from ciba geigy based on butane 1 4 diol araldite rd 2 and from shell chemical corp based on glycerine epon 812 a suitable diepoxide of an alkylcycloalkyl hydrocarbon is vinyl cyclohexene dioxide union carbide erl 4206 and a suitable diepoxide of a cycloalkyl ether is bis 2 3 epoxycyclopentyl ether union carbide erl 0400 the catalyst precursor can be used in amounts of from 0 2 to 35 preferably from 0 5 to 15 parts by weight per 100 parts by weight of epoxidic prepolymer i the aromatic iodonium salts of complex halogenides used as component ii are described in the above mentioned u s pat no 4 173 551 illustrative iodonium salts have the following general structure wherein ar and ar 39 are substituted or non substituted aromatic radicals and mx n is a complex metal halide in which m is b as sb p and the like and x is cl br or f and n is from 4 to 7 typical such salts are 4 4 39 dimethylphenyliodonium hexafluoroarsenate 4 4 39 di t butyl diphenyliodonium hexafluoroarsenate diphenyliodonium hexafluoroarsenate diphenyliodonium hexafluorophosphate diphenyliodonium hexafluoroantimonate.