The release of volatiles during the thermal stress of electric insulating materials

The construction of electrical devices operating under the extreme temperatures requires the knowledge of their particular components behavior during the processing and operation of these devices. The minimum amount of volatile release is one of the requirements imposed on these materials. Thermal analyses (especially Thermogravimetry TG and Differential Thermal Analysis DTA) are considered to be excellent instruments for verification of amount of released volatiles. This verification was realized on the typical materials used for the electrical device manufacturing. Among these materials intended for operation temperatures of 180 degC belong silicone impregnating varnish, two-component composite material (glass fabric + silicone resin) and laminate material composed of aramid-polyimid-aramid combination. Modified test system was applied on specimens in technologically virgin state. The specimens have been exposed to the temperatures of 200, 220, 240, 280 degC for 2 hours. The specific weight losses were observed in particular materials and it depended on temperature and material properties. The combined temperature program was consequently used on exposed materials. It was composed of three different parts applied for three following days. The phases varied in different temperature magnitudes and temperature´s time delays.