The γ-radiolysis of nylons:: Molecular rearrangement and gas production

The gamma-radiolysis of nylons 12, 11, 6/12, 6/9, 6/6, and 6 were investigated. The IR spectra of film samples before and after the gamma-irradiation show the formation of amines, aldehydes, and ketones, and suggest that the cleavage of amide group is one of the major processes of radiolysis. The yields of gaseous products and their evolution from the bulk were measured with a quadrupole mass spectrometer. Four gases were determined as the major radiolytic products and their yields were found to be in the order H-2 > CO > CO2 > CH4 for all the nylons. The relationship between the gas yields and the chemical composition of the monomer unit shows that the H2 yield increases with the relative number of H atoms. The results suggest a random distribution of energy leading to H-2 production. It was found that the yields of CO and CO2 decrease with an increase in the relative number of amide groups on the nylon monomer unit. Since these later products must be derived from the amide group, chain scission and fragmentation at the amide group must decrease with increasing amide contribution to the monomer unit of the polymer chain. The diffusion coefficients of H-2, CO, and CO2 gases in the bulk polymer were determined and the results suggest that post-radiation processes exist in die gamma-radiolysis of nylons.