Chemiluminescence of diglycidyl ether of bisphenol A--norbornene anhydride networks

Networks were prepared by curing diglycidyl ether of bisphenol A (DGEBA) with variable concentrations of norbornene anhydride (NA). Almost completely cured samples with anhydride/epoxide (A/E) molar ratios of respectively 0.8, 0.9, 1.0 and 1.1, and one incompletely cured sample with A/E = 1.0, were studied by chemiluminescence in the temperature range 135-220 degrees C, using isothermal stationary or non-stationary (atmosphere change) exposures. The comparison of kinetic curves of intensity variation reveals: the importance of unreacted epoxide groups as sources of highly emissive radical species, the lowering effect of oxidation products, and the increasing effect of the decrease of macromolecular mobility due to crosslinking in the case of the incompletely cured sample. Most of the features of kinetic curves obtained in non-stationary experiments are explained in terms of radical formation mechanisms during exposure in inert atmosphere. The results show clearly that chemiluminescence is due to reactions of peroxy radicals rather than hydroperoxide groups.