Abstract: Disclosed is a solution of about 2 to about 25 percent by weight based on total solids, of an oligomer having at least two carboxylic acid groups polymerized from an unsaturated fatty acid having at least ten carbon atoms, up to about 20 percent by weight based on total solids of a phenolic resin, an epoxy resin in an amount from about stoichiometric up to about 20 percent excess equivalents of epoxide groups, up to about 2 percent by weight based on total solids of a catalyst and about 10 to about 90 percent by weight based on total solution weight of the solvent. Also disclosed is a prepreg which comprises a substrate impregnated with the solution, dried and cured to the B-stage, and a laminate which comprises a stack of prepregs, pressed under heat and cured to the C-stage.

Abstract: A prepreg useful in flame resistant copper clad printed circuit boards is made by impregnating a porous substrate with an impregnant containing: either a prebrominated epoxy resin or a mixture of a non-halogenated epoxy resin and flame retarding additive containing bromine, and phenolic hydroxyl groups. A phenolic novolac oligomer having an average of over 2.5 phenolic hydroxyl groups per oligomeric unit is used as curing agent. Optionally, a suitable catalyst may be included. The impregnated substrate is heated to cure or advance the resin to the "B"-stage.

Abstract: A prepreg useful as the core in flame resistant cooper clad, composite, printed circuit boards is made by impregnating a porous substrate with an impregnant containing: either a brominated epoxy or epoxy resin and reactive flame retarding additive containing bromine and phenolic hydroxyl groups (e.g., tetrabromobisphenol A), phenolic novolac oligomer as curing agent, unsaturated epoxidized oil, and optionally, a suitable catalyst; and then heating the impregnated substrate to the "B"-stage.