Development of green and dark blue colors in epoxy resins cured with 4,4′-diaminodiphenylmethane

From a study of the oxidation of bisphenol-A epoxy resin cured with DDM (4,4′-diaminodiphenylmethane), it has been shown that the development of greenish-blue colors is due to an initial reaction between molecular oxygen and secondary amine groups. A full reaction scheme is suggested and supporting evidence, in the form of UV/visible, infrared, and ESR spectra, is presented.