Changes in dielectric properties of elastomer by irradiation

Using tetrafluoroethylene-propylene copolymer as the sample, the effects that the quantity of polar radicals and the change of cross-link density accompanying irradiation exerted to its dielectric characteristics were examined by dividing into three cases. (1) When the cross-link density lowered and polar radicals increased while severance and cross-linking were repeated: In the gamma and heat irradiation at room temperature, as for the G-value of severance and cross-linking, 1.38 and 1.28 were obtained, respectively, and 2.16 was obtained as the G-value of C=O formation. In this case, with the amount of irradiation, the dispersion intensity increased, and the relaxation time became long. (2) In the case of irradiating the samples having different cross-link density with gamma ray at 0.2 MGy, although the dependence of the dispersion intensity on the initial cross-link density was small, the relaxation time became longer as the initial cross-link density was higher. (3) When the amounts of cross-linking and severance were the same, and the amount of C=O increased, the dispersion intensity became high, and the relaxation time became long. From the above results, it was concluded that the dispersion intensity increased with the amount of C=O radical, and the relaxation time became longer as the chain length of free ends was shorter. (K.I.)