Epoxy resin(s) with anhydride and polybutadiene-maleic anhydride adduct

A toughened epoxy resin system having glass transition temperatures T.sub.g in the range of from about 250.degree. C. to 350.degree. C., said resin system being prepared from a blend comprising the following components:

• (1) An epoxy resin component selected from the group consisting of
• a) a single epoxy resin having an epoxy functionality greater than two epoxy groups per molecule;
• and
• b) a mixture of epoxy resins so selected that all of the epoxy resins in said mixture have an epoxy functionality of at least two epoxy groups per molecule and that said mixture has an average epoxy functionality greater than 2 epoxy groups per molecule;
• (2) An anhydride hardener component consisting essentially of a mixture of
• (a) A bicycloalkene dicarboxylic acid anhydride;
• and
• (b) A 1,2-polybutadiene-maleic anhydride adduct containing from about 15 to 25% combined maleic anhydride and having an equivalent weight in the range of about 400 to 700;
• the stoichiometric ratio of (2)(a) to (2)(b) being from 75 to 1 equivalents to 2 to 1 equivalents, and the stoichiometric ratio of said anhydride hardener component (2) to said epoxy resin component (1) being from about 0.7 equivalents of said anhydride hardener component to 1 equivalent of said epoxy resin component;
• (3) An epoxy accelerator selected from the group consisting of dialkyl imidazolethiones, dialkylimidazoles, tertiary amines, Lewis bases, dicyandiamide, and mixtures thereof, and alternately Lewis acids, the total content of accelerator being from about 0.1 to 5% by weight of total epoxy resin system;
• said blend being subjected to a preliminary cure at from about 80.degree. C. to 120.degree. C. till said blend has gelled, and then to further curing at temperatures of from 200 to 300.degree. C. till curing is complete, thereby obtaining final toughened solid resin.