Factors determining the partial discharge resistance of polymers

In this research, the partial discharge resistance was examined for eight kinds of polymer samples, namely, low-density polyethylene, polypropylene, poly-methyl-pentene, atactic polystyrene, syndiotactic polystyrene, polyethylene terephthalate, polyethylene naphthalate, and polyimide. An ac 500-Hz voltage with a designated value was applied to a sample sheet sandwiched between a pair of IEC (b) electrodes at 353 K (80°C) and 30% relative humidity for a designated period. The sheet surface degraded by partial discharges was then observed by a mechanical surface profilometer to measure the shape, from which the whole eroded volume was estimated. As a result, it has been clarified that polymers can exhibit superior partial discharge resistance when their melting point, molecular weight of chain repeating unit, density, weight ratio of benzene rings, and crystallinity are high.