The γ-Radiolysis of Nylons:  Molecular Rearrangement and Gas Production

Abstract

The γ-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 γ-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 > CO 2 > CH 4 for all the nylons. The relationship between the gas yields and the chemical composition of the monomer unit shows that the H 2 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 CO 2 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 CO 2 gases in the bulk polymer were determined and the results suggest that post-radiation processes exist in the γ-radiolysis of nylons.

ESR study of gamma irradiated 2-methyl nylon3

“…As the unpaired electron on the NH group is very active species, the intermediate product abstracts a hydrogen atom (or catch a hydrogen radical generated by irradiation) from vicinal chains to form stable primary amide group. Formation of primary amide groups in polyamides have also been reported by Chang and LaVerne (2002). As this reaction is very fast, no ESR signal was observed for the intermediate product.…”

Nylon 6,12 fibers under low-dose gamma irradiation

“…In previous works, a degradation mechanism based on chain scission, which takes into account the Compton effect, is proposed [9] . The degradation is observed in the amorphous zone of the fi ber [5,7,10,11] , which includes scission of amide groups [4, 12 -14] . As a consequence, a soluble mixture of low-molecular-weight oligomers and high-molecular-weight repolymerized fi bers is obtained [5,14] .…”

The radiolysis of poly(4-vinylpyridine) quaternary salt ion exchange resins

“…The radiolysis of organic polymer materials leads to the production of gases, especially H 2 , depending on the nature of polymers or the type of ionizing radiation [11][12][13][14][15][16][17]. The production of H 2 can be explained from simple radical chemistry (e.g., H atom-H atom combination, H atom abstraction, and disproportionation) following C-H bond breakage due to the energy deposited by the passage of ionizing radiation or from the unimolecular decomposition of excited singlet states [13,16].…”