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 endgroups 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-CH2- structural units (stage III). Terminal carboxyl groups show the general tendency to shift the induction time of the third stage to a shorter time.