Development of Surface Dielectric Relaxation Measurement Technique and Its Application to Non-destructive Evaluation of Oil Degraded Commercial Rubber

ISHII Masashi

doi:10.2116/bunsekikagaku.61.403

A new electric characterization technique probing the dielectric relaxation intrinsic to surfaces was proposed. Although contact electrodes are ought to be used in conventional dielectric relaxation measurements, non-contact electrodes maintaining the original surface are introduced in this technique, ‘surface dielectric relaxation’. A buffer liquid filled into a gap made by the non-contact configuration realized appropriate electric coupling between the surface and the electrodes, and a uniform charge distribution on the surface. The electric stabilization revealed the dielectric relaxation of surface to be different from that of underlying bulk. As analytical techniques, two kinds of spectral expression of the relaxation were discussed : complex impedance with respect to probing frequency was sensitive to the surface polarization, and complex capacitance versus frequency indicated interfacial polarization between bulk and surface. The surface-sensitive analysis using complex impedance was applied to a non-destructive evaluation of oil degraded natural rubber. It was found that the cut-off frequency, defined by the frequency with real part of impedance being equal to imaginary part was proportional to tensile strength weakening by the oil degradation. The proportionality coefficient indicated that the cut-off frequency of the surface had an advantageous dynamic range of three orders of magnitude wider than that of the bulk.

Development of Surface Dielectric Relaxation Measurement Technique and Its Application to Non-destructive Evaluation of Oil Degraded Commercial Rubber

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