synopsisDegradation of nylon 66 films of different morphologies was studied in the presence of nitrogen dioxide, ozone, oxygen, and near-ultraviolet radiation (A > 2900 8). Films cast from formio acid solution showed normal random degradation, whereas films cast from benzyl alcohol solutions and dried a t elevated temperatures under nitrogen showed very strongly inhibited random degradation. This inhibition may be due to protection of peptide groups by hydrogen bonding with benzaldehyde or benzoic acid or even to their chemical reactions at elevated temperatures. Oxygen was not rigorously excluded during preparation of the films. Degradation of nylon 66 films cast from formic acid solutions a t room temperature containing benzaldehyde or benzoic acid, respectively, is also inhibited. The energy of activation for inhibited degradation in presence of nitrogen dioxide is relatively small, indicating that the process is either controlled by diffusion of polymer radicals from medium cages or by diffusion of gases into the polymer. The degradation kinetics can be expressed by "weak"-link random degradation. The weak links are in the present case unprotected peptide groups. The functional relationship between chain scission rate constants and NO, pressure is linear.Photo and photo-oxidative degradation of nylon by irradiation with near ultraviolet light has been studied previously.'J It seems to be agreed that the primary step is the rupture of the peptide bond, which is actually the weakest bond3 in the polymer chain. Many reactions are involved in subsequent steps including peroxidation.No studies have been made concerning the effect of NO2 on nylon 66 in presence of oxygen, ozone, and near-ultraviolet light. Degradation of these polymer films under such conditions is very much influenced by the solvent used and the temperatures employed during formation of such films. It was discovered in this work that films prepared at elevated temperatures from solvents containing benzyl alcohol were strongly protected from degradation. Also, films prepared at room temperature from formic acid solutions containing benzaldehyde or benzoic acid, show inhibition of main-chain scission. T h i s behavior has been studied in some detail, and the results are presented here. versity,