Development of Deterioration Diagnostic Technique of Polymer Electric Insulating Materials Using the Dielectric Measurements with Surface Depth Resolution

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The investigator has been studying the development of deterioration diagnostic technique of polymer electric insulating materials using the dielectric measurements with surface depth resolution. Application of AC high field to the inter-digital electrodes on the polymeric materials, such as silicone rubber, can detect the change in dielectric property during the absorption and de-sorption of water, the amount of ATH filler and the treatment of fillers. Changes in weight, hydrophobicity and surface roughness of the samples are also measured to compare the degradation condition of the specimens.The results are summarized as follows :(1)Dielectric measurement using inter-digital electrodes on a sample surface can detect the change in dielectric loss and capacity of the specimen. The evaluation depth of the dielectric property is proportional to the interval of the electrode fingers. Therefore, dielectric property without direct contact to the sample surface is measurable.(2)High field application of AC commercial frequency can measure the dielectric property for every one cycle of the applied field, however, low field application can detect the changes of polymer condition only at high frequencies(kHz and higher).(3)The measurement of the surface roughness of the samples can define the amount of ATH filler of the materials, however, the change in surface roughness during the de-sorption of water of the samples can not detect.(4)Image analysis of the hydrophobic condition of the sample surface can evaluate the condition of the materials, successfully.(5)Temperature dependence of the hydrophobic level is changed when the measurement temperature is changed. Increasing the sample temperature, hydrophobic level is increased. The changes in HC value are larger when the surface is more hydrophiric.(6)Combination of all above measurement results can evaluate the degradation condition of the polymer materials more accurately.