Abstract: An anhydride-cured epoxy resin (epoxy resin+anhydride curing agent+catalyst) may be fortified (i.e. increased in strength and modulus without being made brittle) by the addition of a carboxylic acid and the reaction product of a carboxylic acid anhydride and a substituted aromatic amine. Strengths as high as 125 MPa and moduli as high as 3500 MPa have been attained, as well as elongations up to 6% and an increase in the ability of the plastic to yield before fracture (ductility), compared to 80 MPa strength, 3000 MPa modulus and 2.4% elongation for the unfortified system (strengths and moduli are tensile).

Abstract: Epoxy resins have been found to be fortified (increased strength and modulus yet not brittle) by compounding(a) a resin-forming polyepoxide,(b) an amine curing agent for (a),(c) a fortifier for (a)+(b) comprising the reaction product of(i) an aromatic amine having an amine group attached to an aromatic ring; and(ii) non-symmetrical diepoxide;the reaction product optionally being further reacted with isocyanates or nitriles, in which case (ii) may be at least partly, a monoepoxide;and heat curing the mixture. Strengths as high as 130-150 MPa and modulus increases to as high as 5000 MPa have been attained along with a ductile mode of fracture.

Abstract: Epoxy resins have been found to be fortified (increased in strength and modulus yet not made brittle) by compounding:(a) a resin-forming polyepoxide(b) an amine curing agent for (a) and(c) a fortifier for (a)+(b) comprising the reaction product of(i) an aromatic polyhydroxy compound and(ii) a diepoxide with one epoxy group less reactive than the other:and heat curing the mixture. Strengths as high as 140 MPa and moduli as high as 4500 MPa have been attained with a ductile mode of failure.

Abstract: The reaction product of (i) an aromatic amide having the amine group of the amide attached to an aromatic ring, and (ii) a mono- or di-epoxide, has been found to be a good fortifier of epoxy resins. Epoxy resins have been found to attain increased strength and modulus (yet not brittle) by compounding:(a) a resin-forming polyepoxide,(b) an amine curing agent for (a), and(c) the above fortifier; and heat curing the mixture. Strengths as high as 130-150 MPa and modulus values to as high as 5000 MPa have been achieved yet with a ductile mode of fracture.