Effect of γ‐irradiation on the electrical properties of cellulose nitrate

Two types of cellulose nitrate were studied; the red cellulose nitrate LR‐115 type 2 and the light pink CA 80–15 samples (Kodak, France). The samples were exposed to different doses of γ‐rays from a 60 Co‐source (from 0.1 – 0.3 Mrad) at room temperature. Conductivity and dielectric constant measurements were carried out. For both nitrate samples (CA 80–15, LR‐115), the electrical conductivities are high in comparison with the unirradiated ones for a dose of 0.1 Mrad, but there is a slight change between 0.1 and 0.2 Mrad doses for CA 80–15 samples while the electrical conductivity is found to be less for 0.3 Mrad due to the damage in the plastic network. Also for the samples LR‐115 the electrical conductivity is lower for doses of 0.2, 0.3 Mrad than that for 0.1 Mrad dose. We notice that the glass transition temperature (T g ) of cellulose nitrate is clearly affected by γ‐irradiation as judged from the anomalies in σ(T) for the two samples which contain different amounts of the pigment. Irradiation of LR‐115 samples resulted in a higher dielectric constant for 0.1 Mrad dose and a lower one for 0.2, 0.3 Mrad doses, but still higher relative to the fresh sample. The dielectric constant of irradiated CA 80–15 samples (0.1, 0.2 Mrad) is found to be high relative to the fresh sample, but for 0.3 Mrad dose the dielectric constant is lower than that of the fresh one.