Abstract
In this review, toughening of epoxy and other thermosetting resins using vinyl polymer modifiers prepared by in situ radical polymerization is described. Radical polymerization of vinyl monomers can proceed in parallel with non radical curing reactions of epoxy resins without mutual interference, and therefore, vinyl polymer modifiers can be radically generated in curing systems of epoxy resins. Modification of epoxy resins by this "in situ polymerization method" increases compatibility between epoxy matrices and modifier polymers and toughens the cured resins with keeping other properties such as modulus and strength. Viscosity of uncured resins is also decreased and toughening process can be simplified by omitting prior preparation of modifier polymers. In situ radical polymerizations of poly(N-phenylmaleimide-co-styrene) (PMS) and PMS derivatives in curing systems of bisphenol A type epoxy resin/acid anhydride and alicyclic epoxy resin/cationic initiator toughen the corresponding cured resins without sacrificing other properties. Toughening of amine- and phenol-cured epoxy resins is achieved by using in situ generated poly(benzyl methacrylate) modifiers. Benzoxazine, cyanate ester and benzoxazine/cyanate resins are also successfully toughened by in situ polymerization method.
