Dielectric Properties and Insulation Diagnosis of Polymers by Ultra-wideband Dielectric and Absorption Spectroscopy

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The objective of this research is the understanding of dielectric properties of polymer films through measurements of permittivity and absorption spectra in an ultrawide-band frequency range.In FY 2012, permittivity spectra were obtained for seven kinds of polymers by the free-space method at GHz frequencies for the purpose of getting useful information on the future ultrafast wideband communication system. The essentials of this research were submitted as a refereed paper. In FY 2013, absorption spectra induced in cross-linked polyethylene by gamma-ray assisted oxidation were analyzed experimentally and numerically using quantum chemical calculations. As a result, it can be clarified that the absorption is due to resonance vibrations induced by the phenomenon that optically inactive lattice vibrations become active through oxidation-induced structural changes. In addition, possibilities of detecting the degradation of ethylene-propylene rubber by THz imaging were also examined.