LOW-TEMPERATURE FAST-NEUTRON AND GAMMA-IRRADIATION OF KAPTON(R) POLYIMIDE FILMS

Structure, chemistry and mechanical properties of Kapton(R) HA and H p olyimide films have been studied after their exposure to fast-neutron and gamma irradiation at a target temperature of 4 K. The fast (E > 0. 1 MeV) neutron fluence was 3.1 x 10(22) n/m(2). X-ray diffraction show ed that irradiation disordered partially crystalline structure of Kapt on(R) H while the structure of Kapton(R) HA remained amorphous under i rradiation. The glass transition temperature (T-g) Of Kapton(R) HA and H increased with irradiation, consistent with the crosslink formation . The increase in T-g was significantly larger in Kapton(R) H. The FT- IR spectrometry showed no new absorptions in the irradiated Kapton(R) HA and H. Shifts in some peak positions have been observed, however. T ensile testing showed that irradiation increased modulus and yield str ength of Kapton(R) HA and H, in agreement with the proposed crosslink formation as the predominant mechanism of radiation hardening. The ext ent of radiation hardening, as evaluated from the total strain at frac ture, was significantly larger in Kapton(R) H.