TRIBOLOGICAL EVALUATION OF LUBRICANTS DEVELOPED FROM SELECTED VEGETABLE BASED OILS FOR INDUSTRIAL APPLICATIONS

Abstract

Mineral oil based lubricants are non-renewable, harmful to health and prone to price fluctuations. Thus, vegetable oils are considered as suitable alternatives to mineral oils for lubricant production. Research on the use of non-edible vegetable oils for lubricant development has become necessary. The tribological evaluation of lubricant developed from non-edible vegetable (jatropha and castor) oils for industrial applications have been carried out in this study. The oils were characterized, modified for suitability and used to develop lubricants for industrial applications. Commercially available mineral oil based lubricant SAE 20/W50 was used as a control. The effect of additives on the tribological performance of jatropha and castor oil based biolubricants developed were also studied. Whereas modification of jatropha oil improved its viscosity but reduced its viscosity index, modification of castor oil greatly reduced its viscosity but improved its viscosity index. Jatropha and castor oils unlike other vegetable oils, possess excellent cold flow properties and modification of the oils further enhanced their cold flow properties. The developed jatropha and castor oil based bioluricants had alkaline pH, high viscosity index, appreciable viscosity, excellent cold flow and corrosion inhibition properties and highly biodegradable with a biodegradability exceeding 80 %, while the mineral oil based lubricant SAE 20/W50 had a poor biodegradability of 35.2 %. The extreme pressure additive cetyl chloride had the most significant effect on the coefficient of friction and anti-wear additive Tricysl Phosphate had the most influential effect on the viscosity index of the jatropha and castor oil based biolubricants. The jatropha and castor oils performed better in friction reduction and wear prevention than the SAE 20W/50 which had 0.114 coeficient of friction and 0.0067 mm3N-1m-1 wear rate. The castor oil had 0.082 coefficient of friction and 0.007 mm3N-1m-1wear rate. The developed jatropha oil biolubricant had coefficient of friction of 0.075 and wear rate of 0.00699 mm3N-1m-1 and was better in friction performance but had similar wear performance with SAE 20W/50. The developed castor oil based biolubricant had 0.067 coefficient of friction and 0.00511 mm3N-1m-1 wear rate and exceeded the SAE 20W/50 in friction and wear performance. Thus, modified and unmodified jatropha and castor oils have been found to be suitable for industrial applications in systems exposed to low temperatures. The developed jatropha and castor oil biolubricants have been found to be suitable environmentally friendly substitutes to mineral oil base lubricant SAE 20/W50 for application in two stroke engines, metal cutting and lubrication of gears in food processing industry.