Wet oxidation of undrawn nylon 66 and model amides

Publisher Website
Google Scholar
Abstract
Undrawn nylon was found to be susceptible within a few days to degradation in wet or humid conditions at temperatures between 50 and 90°C. Model N‐substituted amides, although not affected by these conditions, were attacked by hydrogen peroxide solutions. The degradation proceeded principally by rupture of the bond between the nitrogen of the amide and the carbon of its α‐methylene group, consequent upon oxidation at this carbon. Unsubstituted primary amide, carboxyl, and aldehyde endgroups were formed, together with ammonia by hydrolysis of the oxidized amide. The bond between the α and β carbons of an N‐methylene chain also suffered breakage, giving formic acid and carbon dioxide. The former could also arise by rupture of any initially produced N‐formyl or N‐formoyl amides. The appearance of lactic acid from butylacetamide showed that oxidation could proceed along the N‐alkyl chain. Fragments of suitable size broken from the main chain of nylon became water‐soluble and relatively stable to further attack by air or oxygen. These pieces essentially retained the nylon structure, but possessed two carboxylic ends and an average molecular weight of less than 600. A maximum oxygen uptake of about 30 moles per mole of original amide was calculated, corresponding to complete conversion into these soluble fragments. Significant degradation did not occur for many months at 60°C. in dry conditions or in solutions of 8‐hydroxyquinoline, a process which has been patented. The latter was considered to function by chelating heavy metals into an inactive form and inhibiting peroxide formation.