Jagadeesh K. Mannekote

The Effect of Oxidation on the Tribological Performance of Few Vegetable Oils

Background The use of vegetable oils and their derivatives as lubricant base oils are ever increasing because of sustainability issues and in the context of conservation of nature as they are biodegradable and environmentally friendly. The one disadvantage which is of concern with vegetable oils is their limited oxidative stability. Objectives To study the effect of oxidation on the tribological performance of few vegetable oils by subjecting the oil samples to accelerated ageing in a dark oven at different temperatures, inducing the oxidation under controlled conditions. Method Oils were stored at an elevated temperature in an oven under dark condition and the oxidized oil samples were analyzed in terms of various properties. Results and conclusions The samples were analyzed for the changes in viscosity, percentage of free fatty acid, peroxide number and were compared with fresh oils samples. Further tribological property was also evaluated and the observed differences were linked to formation of oxidation products like peroxides, kinetics of the oxidation with reference to ageing temperature.

Tribology of Green Lubricants

Increased demand to protect the environment from mineral oil based lubricants has necessitated replacing them with products derived from natural resources. In addition to this a combination of environmental, health, and economic challenges has also renewed interest in the development and use of green lubricants over the last two decades. This chapter gives an overview of green lubricants beginning from their ancient use to the challenges prospective of the lubricant industry. The review includes structural and chemical properties of important vegetable oils and chemical modification of vegetable oils. Tribological behavior of products based on vegetable oils, green additives, and ionic liquids under varied testing conditions is also presented. This study also gives an insight into the testing procedures and sustainability aspects of green lubricants and additives.

Influence of Chemical Structure on the Boundary Lubrication Properties of Vegetable Oils

Vegetable oils are increasingly used as lubricant base oils, because of sustainability issues and regulations. In present study coconut, palm, sunflower and castor oils were used to represent different levels of unsaturation, where as castor oil was selected to represent influence of hydroxyl group. The effect of oxidation on the boundary lubrication properties was evaluated by subjecting the oils to accelerated ageing at 333,353 and 373 k according to AOCS method. The experiments were carried out by using of four ball tester increase in observed wear scar diameter with temperature was more with oil having higher percentage of unsaturated fatty acids. At the same time it was also observed that increase in wear scar diameter with temperature was more with castor oil compared to other oil samples. The poor boundary lubrication properties observed with aged oil samples was possibly due to the deterioration of the triglyceride structure.Copyright