Thermooxidation yellowing of aliphatic polyamides

Abstract During the thermo‐oxidation at 90°C of unsubstituted or N‐substituted aliphatic polyamides, formation of products which absorb in the UV and visible regions is observed. These products are photo‐instable either at short wavelengths or at long wavelengths and their photo‐reactivity is wavelength dependent. These oxidized groups are identified as crotonized aldehydic groups (CH  CH)2 or 3 CHO similar to those formed in the photo‐oxidation at short wavelengths of aliphatic polyamides.