Effect of Oxidation of Soybean oil used in Biodegradable Lubricant

Soybean oil is a promising base stock for biodegradable lubricants because of its renewable origin, high lubricity, and low environmental impact. However, its application is limited by poor oxidative stability. The unsaturated fatty acids in soybean oil are highly susceptible to oxidation, especially under elevated temperatures and in the presence of oxygen, metal catalysts, or light. Oxidation initiates free-radical chain reactions that lead to the formation of hydroperoxides, aldehydes, ketones, and polymeric compounds. These degradation products adversely affect lubricant performance by increasing acidity, viscosity, and sludge formation, while reducing lubricity and service life. Consequently, oxidation can cause corrosion, deposit buildup, and failure of lubricated components. To address this limitation, chemical modifications such as epoxidation, transesterification, and the incorporation of antioxidants are commonly applied to improve stability. Understanding the mechanisms and effects of oxidation in soybean oil is essential for developing durable, high-performance biodegradable lubricants.