| Abstract: | Low dielectric loss polyethylenes have been produced by γ-radiation polymerization of oxygen-free ethylene monomers. Dielectric measurements were made at 500 MHz and 20°C. The lowest dielectric loss tangent of the polyethylene was 3.3 × 10?5. Polar groups contributing to the dielectric loss have been found to be carbonyl groups, terminal vinyl groups, methyl groups, and hydroxyl groups contained in the polyethylene. The contribution of each group to the loss tangent has been calculated from a comparison of the variation of the loss tangent with the content of each group as determined by infrared analysis. It has been found that the reduction of the loss tangent is mainly due to the decrease in the concentrations of the carbonyl groups and the terminal vinyl groups and that the presence of a considerable amount of the hydroxyl groups prevents a further reduction of the loss in the polyethylenes. The results obtained from the analysis of the radiation-polymerized polyethylenes were applied to commercially available polyethylenes. |
