Abstract :
The intrinsic electric strength of certain solid dielectrics has been measured for comparison with theories of electronic breakdown and on account of the bearing on industrial applications of dielectrics. Attempts to measure the strength of paraffins were unsuccessful, except for material oriented by pressing, because of the poor mechanical properties of such substances. Satisfactory tests were made on polythene, which gave a strength of about 6.5×106 V/cm at room temperature to ¿190° C, and on polyvinyl chloride-acetate, the strength of which increased from about 6.5×106 V/cm at room temperature to 12×106 V/cm at ¿190° C. The polythene was crystalline and the results correspond to those for inorganic crystalline materials, and with the theory for such crystals. The copolymer was amorphous, its behaviour is similar to that of varnishes, and may be explained by Fröhlich´s most recent development of the theory for amorphous substances.
