FT–IR spectroscopic study on the photo- and photooxidative degradation of nylons (original) (raw)

The progress of photo-and photooxidative degradation of nylon films were studied by FT-IR spectroscopy. The gases evolved from the photolysis of various nylons and their model amides were also analyzed. The formation of double bonds, changes of crystallinity, and the effect of amino and carboxyl end groups has been studied and discussed. The band shapes of the IR spectra pertaining to the carbonyl groups formed by thermal oxidation or photooxidation were found to be very similar, suggesting that the two oxidation mechanisms might be similar. The broadness of these bands indicates that the carbonyl groups may belong to more than one species. The photodegradation of nylons containing purposely inserted carbonyl groups formed-CH=CH, groups. Carbonyl groups formed during oxidation, and present either as keto groups or part of N-acylamide units make nylons susceptible to degradation reactions entailing mainly a Nonish type I1 mechanism. From ESR s t~d i e s ,~,~ kinetic studies,6 and chemical analyses,' the photolysis mechanisms were suggested to occur by degradation involving direct cleavage of the amide bond according to a Nonish Type I mechanism. Moore suggested that both Type I and Type I1 mechanisms occurred in the degradation of nylons.8 Recently, Mazzocchi and Bowen studied the photolysis of N-alkylamides in solution by analyzing the products and concluded that the Type I process was predominant and the Type I1 process was quite ineffi~ient.~ They rationalized *To whom correspondence should be addressed.