Comparative TG/DTG/DTA+FTIR studies concerning the stability of some mineral and vegetable electro-insulating fluids

Abstract

Thermal TG/DTG/DTA analysis coupled with FTIR spectroscopy was applied to some sorts of mineral and vegetable oils used in electrical equipment. On heating in inert atmosphere, it was observed that the mineral oils vaporize, while the vegetable oils undergo hydrolysis, yielding fatty acids as main volatiles, as indicated by FTIR. In synthetic air, the FTIR spectra of gaseous products confirm the presence of similar oxidation products, both for mineral and vegetable oils. The TG results indicated that the vegetable-based oils exhibit a substantially higher thermal stability than the mineral oils. The presence or absence of antioxidant inhibitors in these oils greatly influences the onset of the oxidation process in air environment factor, as results from the DTA results.