| abstract |
The curing agent composition comprises an anhydride and approximately equimolar amounts of a tertiary amine or imidazole and a carboxylic acid, wherein the amine is 1-piperidinylethanol (N-hydroxyethyl-piperi) represented by structure (I) din, NHEP) or imidazole represented by structure (I): wherein R 1 = H, C1-C20 straight-chain or branched alkyl, or monocyclic aryl; R 2 = C1-C20 straight-chain or branched alkyl, or monocyclic aryl. Carboxylic acids are represented by RCOOH; R=C1-C20 straight-chain or branched alkyl, or monocyclic aryl. The composition includes a lower ratio (1:0.4-0.6) of epoxy resin to anhydride than is typically used (1:0.8-1.1). Additionally, higher loadings of hindrance latent tertiary amines or imidazoles (wt % ratio of amine and carboxylic acid to anhydride combined ˜10%) are used in combination with carboxylic acids. Full cure can be achieved in less than 2 hours at significantly lower temperatures (˜100° C.) with these compositions. |