Degradation of electrical properties of organic industrial laminates due to moisture absorption

The influence on certain important electrical properties such as insulation resistance, breakdown voltage, comparative tracking index (CTI), and arc resistance in industrial organic laminates is discussed. Four different types of laminates-paper phenolic, glass-epoxy, glass-melanine, and sheet molding compounds-were selected for the investigation. The influence of araldite coating on the sides of the specimens was also investigated for some of the properties mentioned above. It is shown that glass-epoxy laminates and paper phenolic laminates exhibit very good and very poor performance, respectively. The behavior of CTI and the arc resistance of the laminates with respect to electrode material suggest that the physical processes responsible for the degradation of the material are entirely different than for the other properties. The araldite coating did not improve the properties. Instead it had an adverse effect on most of the characteristics