Inhibited degradation of nylon 66 in presence of nitrogen dioxide,ozone, air,and near—ultraviolet radiation

Degradation of nylon 66 films of different morphologies was studied in the presence of nitrogen dioxide, ozone, oxygen, and near-ultraviolet radiation (λ > 2900 Å). Films cast from formic acid solution showed normal random degradation, whereas films cast from benzyl alcohol solutions and dried at 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 at 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 NO₂ pressure is linear.