Abstract: Vinyl ester resins of the type already having reactive liquid polymers reacted into the backbone of the resins, are cured in the presence of a reactive liquid polymer additive admixed with the prereacted vinyl ester resin. Heating of the system during cure causes the reactive liquid polymer additive to miscibilize with the vinyl ester base resin. The vinyl ester resin modified in the manner described above shows a significant enhancement in toughness as measured by fracture energy over unmodified counterparts or counterparts modified by known methods of adduction or admixing alone.

Abstract: Vinyl ester resins of the type already having reactive liquid polymers reacted into the backbone of the resins, are cured in the presence of a reactive liquid polymer additive admixed with the prereacted vinyl ester resin. Heating of the system during cure causes the reactive liquid polymer additive to miscibilize with the vinyl ester base resin. The vinyl ester resin modified in the manner described above shows a significant enhancement in toughness as measured by fracture energy over unmodified counterparts or counterparts modified by known methods of adduction or admixing alone.

Abstract: Curable epoxy resins are toughened with statistical monofunctional carboxyl, amine or epoxy-terminated reactive polymers and have low viscosities before cure thereby making them useful in a wide range of applications. The cured epoxy resin systems which are modified by the statistical monofunctional reactive polymers have physical properties, such as adhesion and elongation, generally equal to or better than those of cured epoxy resin systems modified with statistical difunctional reactive polymers. A process of preparation of the modified epoxy resin systems of the present invention includes admixing an epoxy resin with a statistical monofunctional carboxyl, amine, or epoxy-terminated reactive polymer in the presence of a curing agent and reaction therewith to form the toughened, cured epoxy resin system.