A Green Approach to Stabilizing Soybean Oil Dielectric Fluids: The Role of Methyl Carnosate

Natural ester dielectric fluids are increasingly favored as sustainable alternatives to mineral oils; however, their susceptibility to oxidation remains a major challenge. Conventional stabilization methods using synthetic antioxidants often pose health and environmental concerns. This study explores the use of methyl carnosate (MC), a bio-based antioxidant, to enhance the oxidation stability of soybean oil (SO). The addition of MC increases the oxidation onset temperature of SO by nearly 20 °C and effectively mitigates the rise in kinematic viscosity and soluble acidity during accelerated aging at 120 °C. These parameters remain significantly lower compared to neat SO and the commercial product FR3®fluid. Mechanistic investigations reveal that MC effectively inhibits the transfer of allylic and bisallylic hydrogens, thereby delaying the formation of aldehydes generated from peroxide decomposition. This study underscores the potential of MC as a sustainable and effective additive for enhancing the oxidation stability of natural ester dielectric fluids.