Method of preparing toughened epoxy polymers
AssigneeThe Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom and Northern Ireland
InventorsSteven J. Shaw, David A. Tod
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Abstract
Toughened epoxy resins are prepared by curing a mixture of epoxy resin, a liquid carboxyl-terminated elastomer, and, as curing agent, a non-aromatic heterocyclic amine or a salt thereof. Cure is in two stages, the first stage at a temperature of at least 135.degree. C. for less than two hours to provide a partly cured formulation comprising phase-separated rubbery particles in an epoxy resin matrix, and a second stage of completing the cure.
Claims13
A method of preparing a toughened epoxy polymer from an epoxy resin formulation, said formulation comprising a mixture of 100 parts by weight of an epoxy resin, from 12.5 to 25 parts by weight of a liquid carboxyl-terminated elastomer and from 0.5 to 15 parts by weight of curing agent, said curing agent being selected from non-aromatic heterocyclic amines and salts thereof having selectivity for a carboxy-epoxide reaction, characterised in that the method comprises curing the formulation in two stages, the first stage comprising curing the formulation at a temperature of at lest 135.degree. C. for less than 2 hours to provide a partly cured formulation comprising phase-separated rubbery particles in an epoxy resin matrix, and the second stage comprising curing the formulation for a further period until the epoxy resin matrix is cured.
A toughened epoxy polymer, prepared from an epoxy resin formulation comprising a mixture of 100 parts by weight of an epoxy resin, from 12.5 to 25 parts by weight of a liquid carboxy-terminated elastomer and from 0.5 to 12 parts by weight of a curing agent, said curing agent being selected from non-aromatic heterocyclic amines and salts thereof having selectivity for a carboxy-epoxide reaction, which polymer has a fracture energy at 20.degree. C. of from about 4.32 to about 13.82 kJm.sup.-2.
Dependencies are inferred from the claim text.