The Application of the Thermogravimetric Analysis (tga) and of the Differential Thermal Analysis (dta) for Rapid Thermal Endurance Testing of Electrical Insulating Materials

The thermogravimetric analysis (TGA) and the differential thermal analysis (DTA) were applied to investigations of aging processes in some electroinsulating polymeric materials (glass reinforced epoxy resin, NBR ( two sorts), styrenated unsatured polyester resin, hydrogenated NBR (T80), polychloroprene rubber , EPR) and to the measurement of aging reaction rates. It is shown that thermal analysis curves (TG and DTA) can be used for planning thermally accelerated aging experiments which are used for the thermal lifetime evaluation by the method given in IEC 216. Some results concerning isothermal and non-isothermal aging of the above mentioned materials are presented and discussed. The obtained results show that, except EPR, for each investigated material, the value of activation energy corresponding to isothermal degradation of a mechanical property is close to the value of activation energy rapid evaluated from TGA or DTA data. The rapid method for thermal lifetime evaluation which consists in the rapid determination of the activation energy from thermal analysis data and the plotting of only one isotherm of accelerated aging, corresponding to the maximum admitted temperature for accelerated aging, was checked. The results presented in this work show that the TGA and DTA methods should be included among the analytical methods used for thermal endurance testing of insulating materials.