| Abstract: | In order to predict the safe service life of a polymer from its rate of oxidation, a detailed understanding of degradation and stabilization reactions in the induction period is required. The mechanism by which an oxidizing polymer emits weak visible light (chemiluminescence) is reviewed and the use of the technique to study the early stages of the oxidation of nylon 66 and polypropylene is considered. Steady-state chemiluminescence experiments are described to measure the activation energy of initiation of nylon 66 oxidation and to study the mechanism of the dark reaction of a hindered amine light stabilizer (and its nitroxyl radical) with polypropylene hydroperoxide. Non-stationary experiments, in which the steady state is perturbed by UV irradiation and gas switching, demonstrate the reactions of long lived alkyl radicals in the induction period. The observation of stress-induced chemiluminescence from nylon 66 shows the effect of even a low fiber load is to greatly increase the rate of oxidation. |
