Elastohydrodynamic study of vegetable oil-polyalphaolefin blends

Authors: Bantchev, Grigor; Biresaw, Girma

Submitted to: Lubrication Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2008
Publication Date: 10/1/2008
Citation: Bantchev, G.B., Biresaw, G. 2008. Elastohydrodynamic Study of Vegetable Oil-polyalphaolefin Blends. Lubrication Science. 20(4):283-297.

Interpretive Summary: Continuous rise in the price of petroleum and tightening environmental regulations have increased interest in farm-based lubricants. Successful application of vegetable oils in lubrication requires that their properties are well characterized and controlled for the various demanding processes. One of the drawbacks of using vegetable oils in lubrication is their relatively narrow range of properties, such as viscosity. In this work, we characterized the properties of blends of vegetable oils with petroleum-based synthetic oils. The result showed that blending increases the range of properties, thereby allowing vegetable oils to be used in multitude of new lubricant applications. The study also investigated various theoretical models for predicting the properties of blends of vegetable oils with synthetic lubricants. The models provide guidelines for selecting optimal blend compositions for the various lubrication applications. The results of this study demonstrates that blending allows vegetable oils to be used in lubrication application processes that until now were possible only with synthetic lubricants.

Technical Abstract: Two polyalphaolefins (PAOs), of higher and lower viscosity than vegetable oils, were used to make binary blends of varying compositions with soybean and canola oils. The pure oils and the blends were used in viscosity and film thickness investigations. The effect of composition and temperature on viscosity were found to agree well with the theoretical predictions of a simple mixing law. The film thicknesses of the various blends under EHD conditions were measured at 20 N load, and varying entrainment speeds and temperatures. From the data, pressure-viscosity coefficients, alpha, as a function composition and temperature were obtained. The resulting alpha values were compared with theoretical predictions. Experimental values of alpha as a function of composition showed a slight negative or no deviation from the values predicted by an ideal mixing model. On the other hand, experimental values of alpha displayed a mild decrease with increasing temperature while the model predicted a sharp decrease with increasing temperature.