Effect of cryogenic irradiation on the mechanical properties of organic insulator films

The object of this study is to acquire data on radiation damage of organic insulator films at low temperature. The specimens used were thin films of polyphenylene sulfide (PPS), polyarylether etherketone (PEEK), polyethylene terephthalate (PET), and polypyromellitimide (PPMI, Kapton H). Experiments were mainly done with PPS, since at the present there is little information on the cryogenic properties and radiation effects for this material. Irradiation of the films was performed at 20 K in the lowtemperature irradiation facility of the Kyoto University Reactor and the mechanical properties of the films were measured at 77 K. In tensile tests of PPS films, both the unirradiated and irradiated specimens showed a gradual increase in strength beyond the elastic limit at all test temperatures. The tensile strength and the ultimate elongation of PPS films were almost independent of irradiation dose up to 8 MGy at 20 K. For comparison, similar mechanical tests were carried out with irradiated films of PEEK, PET, and PPMI. As far as the present experiments are concerned the radiation tolerance of PPS films has been proved to be on the same level as that of PEEK and PPMI films