Patent ID: 8877866

Claim:
A thermosettable composition having improved adhesion to metal substrates when cured comprising: (a) at least one curable flame retardant epoxy resin comprising a diglycidyl ether of tetrabromobisphenol A and/or a phosphorus-containing epoxy resin; (b) at least one hardener, each hardener having less than 1 primary amine group per molecule and not more than 1 secondary amine group per molecule, the hardener comprising i) at least one polyhydroxy hydrocarbon and/or a hydrocarbon compound capable of generating multiple hydroxy groups per molecule during curing of the thermosettable material, and ii) a poly(acid anhydride) hydrocarbon selected from the group consisting of a copolymer of an ethylenically unsaturated anhydride and an elastomer, a maleic anhydride adduct of methylcyclopentadiene, and combinations thereof; and (c) at least one triblock copolymer comprising at least one elastomeric block and at least one acrylic block; wherein the composition provides a prepreg formulation having a prepreg minimum melt viscosity of at least 20 Pa·s at a prepreg gel time of 60 seconds; and wherein the composition provides a formulation having a copper peel strength of at least 10 N/cm when cured; and wherein, during curing of the thermosetting material, the weight ratio of the total amount of the poly(acid anhydride) hydrocarbon to the polyhydroxy hydrocarbon and/or the compound capable of generating multiple hydroxyl groups per molecule is not greater than 1:3.