Chemiluminescence from oxidation of polyamide 6,6. I. The oxidation of pure polyamide

The chemiluminescence (CL) accompanying the oxidation of both polyamide 6,6 and a model diamide with no reactive end-groups is reported. CL emission for neat diamide starts after melting of crystallites, and the shapes of the intensity-time curve show a sigmoidal behaviour, typical of the chain oxidation of organic compounds. Adipic acid shortens induction period of chemiluminescence increase. A bimolecular hydroperoxide decomposition model can successfully describe the kinetic runs of CL. Polyamide 6,6 CL runs are apparently composed of 3 different kinetic stages: a decay from an initial CL value, due to the termination of peroxyl radicals being trapped in the polymer after processing and storage (stage I), a sudden increase of emission, related to depletion of terminal amino groups (stage II), and a major maximum of emission, decaying again to a lower level of chemiluminescence, indicating chain oxidation of –CONH–CH 2– structural units (stage III). Terminal carboxyl groups show the general tendency to shift the induction time of the third stage to a shorter time.