Via Performance to Degradation: Oxidation Mechanism of Biodegradable Polyalphaolefin Base Oil for Electric Drive Systems

Abstract

An additive-free, low-viscosity polyalphaolefin (PAO) has been oxidized under pure oxygen at elevated pressure and temperature. This biodegradable PAO base oil is a promising candidate for use as a motor-gear lubricant in electrical drive systems. The oxidation behavior is systematically investigated to evaluate its thermal stability and long-term performance. Rheological measurements are performed to assess viscosity, water content is quantified, tribological tests determine the coefficient of friction, and Fourier-transform infrared spectroscopy is used to monitor chemical changes during oxidation. All analytical methods consistently revealed a two-step oxidative degradation process. It is proposed that the first stage involves the formation of carbonyl compounds and water without compromising lubrication properties, while the second stage—triggered by hydrolysis of oxidation products—leads to chain scission and initiates the desired degradation. This two-stage mechanism is discussed in the context of technological functionality and sustainability requirements for next-generation electric drive lubricants.