Influence of Thermal Oxidation on Tribological Properties of Rapeseed oil

Abstract

Ageing and degradation of lubricant due to oxidation usually is undesirable. However, few studies relate oil oxidation to its tribological properties. In this investigation, additive-free Low Erucic Acid Rapeseed oil (LEAR) was oxidised and its anti wear properties tested. Four samples with different degrees of oxidation were produced by bubbling dry air through LEAR in glass vessel at 120 °C. Kinematic viscosity and acidity were measured as well. Friction tests were conducted using MAST-1 apparatus (equivalent to Four-Ball AW tester). Torque and temperature were monitored throughout the tribotest, and wear scars were analyzed using SEM. The results showed that oxidation has a significant effect on the lubricity of LEAR. Wear scar diameters showed major increase even after low extent of oxidation, while viscosity went up only slightly. Severe oxidation resulted in much higher viscosity. The wear scar diameters, however, became smaller than those of unoxidised LEAR. Microscopy and torque data also confirmed that late stages of oxidation might lead to improved lubricity.