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

High-energy ions of H, He, C, O, Ne, Ar with 10-460 MeV from an AVF cyclotr on accelerator were used to irradiate polymer films of 100x100 mm(2) area b y beam scanning. The changes of mechanical properties and also the chemical reactions such as chain scission or double bond formation were investigate d. The linear energy transfer (LET) dependence of the changes of polymer pr operties was found to be very small when compared with adsorbed dose and wa s the same as that under gamma ray or electron beam irradiation. It means t hat the probability and also the mechanisms of chemical reaction should be almost the same even if LET was different. The ion energy would be disperse d widely in the polymer material, where the chemical reaction proceeds rath er homogeneously. The chemical reaction sites are not so concentrated in a local area under high LET radiation, and the concentration in the local are a might be the same as under low LET radiation. If the track model along th e ion path is applied, the diameter may be a few 100 nm for C5+ (220 MeV) i on irradiation and is proportional to the square root of LET. (C) 1999 Else vier Science B.V. All rights reserved.