Ion beam irradiation effect on polymers. LET dependence on the chemical reactions and change of mechanical properties

Abstract

High-energy ions of H, He, C, O, Ne, Ar with 10–460 MeV from an AVF cyclotron accelerator were used to irradiate polymer films of 100 × 100 mm 2 area by beam scanning. The changes of mechanical properties and also the chemical reactions such as chain scission or double bond formation were investigated. The linear energy transfer (LET) dependence of the changes of polymer properties was found to be very small when compared with adsorbed dose and was the same as that under gamma ray or electron beam irradiation. It means that the probability and also the mechanisms of chemical reaction should be almost the same even if LET was different. The ion energy would be dispersed widely in the polymer material, where the chemical reaction proceeds rather homogeneously. The chemical reaction sites are not so concentrated in a local area under high LET radiation, and the concentration in the local area might be the same as under low LET radiation. If the track model along the ion path is applied, the diameter may be a few 100 nm for C 5+ (220 MeV) ion irradiation and is proportional to the square root of LET.