Low temperature rearrangement of amine cured epoxy resins

Studies are reported on the rearrangements which occur in epoxy resins when heated above 497 K. The nature of the processes which occur in the resin and in model compounds is discussed with reference to changes in the ultraviolet, infra-red and ¹³C and ¹H NMR spectra. Chain scission is preceded by dehydration of the glycidyl segment and occurs at the CN and OC bonds, generating phenoxy radicals in the latter case. The observed coloration of the resin at high temperatures is associated with the formation of a polyenyl structure and the possible generation of quinoid and cyclic conjugated nitrogen-containing aromatic ring structures.