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

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.