A Study of Ageing and Gelling in Natural Ester Oils

Two natural ester-based transformer fluids derived from soybean oil and rapeseed oil were compared to their edible equivalents. Oxidative ageing was performed in the presence of Kraft paper at 130 °C and some samples contained copper. It was found that both edible oils, particularly soybean oil, showed increased acidity and viscosity after ageing in the presence of copper. Further tests showed that both butyl hydroxytoluene (BHT), which is a common inhibitor for mineral oil but is moderately toxic, and Irganox 1010, which is non-toxic, successfully mitigated the adverse effects of oxidation in edible soybean oil. The study highlights some of the detrimental effects of oxidation in natural ester oils and shows that Irganox 1010 provides a non-toxic alternative to BHT for stabilizing ester oils.