Effect of chemical structure on film-forming properties of seed oils

Authors: Biresaw, Girma; Bantchev, Grigor

Submitted to: Journal of Synthetic Lubrication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2008
Publication Date: 11/4/2008
Citation: Biresaw, G., Bantchev, G.B. 2008. Effect of Chemical Structure on Film-forming Properties of Seed Oils. Journal of Synthetic Lubrication. 25(4):159-183.

Interpretive Summary: Currently, there is an oversupply of farm products that have suppressed the price that farmers get for their crops. One way of countering this trend is developing new uses for agricultural products. Various new uses for agricultural products are under active investigation and development. One of the most promising new application area for farm-based products is in lubrication. Over 3 billion gallons of lubricants are consumed annually in the US, almost all of which are manufactured exclusively from petroleum-based raw materials. Successful replacement of some or all of the current lubricants with ag-based lubricants will provide new market for surplus crops. In the work described here, the film forming properties of lubricants from various seed oils were investigated and compared to conventional petroleum- based lubricants. The result indicated that the effect of crop-to-crop and within crop variations in chemical structure of seed oils on their lubrication properties can be quantified. The ability to relate chemical structure to lubrication property is essential for rapid development of ag-based lubricants for metalworking, motor oil, hydraulics, and other applications.

Technical Abstract: The film thickness of seven seed oils and two petroleum-based oils of varying chemical structures, was investigated by the method of optical interferometry under pure rolling conditions, and various combinations of entrainment speed (u), load, and temperature. The measured film thickness (h measured) were then compared to that calculated (h calculated) using the Hamrock-Dowson (H-D) equation. The result showed that the H-D equation adequately and without exception predicted h measured in the high entrainment speed region (u > 0.1 m/s), but not in the low entrainment speed region (u < 0.1 m/s). In order to understand these deviations further, the chemical structural variabilities of the oils related to polarity (functional groups), unsaturation (double bonds), and molecular weight (chain length) were determined using quantitative empirical parameters. The effect of variability in the viscosity and chemical structure parameters of the oils on film thickness in the low entrainment speed region was then examined. The result of this examination indicated that, in the low entrainment speed region, the film thickness of seed oils: (a) rarely correlates with viscosity as proposed by the H-D equation, (b) increased with decreasing polarity of the oil, and (c) increases with decreasing degree of unsaturation of the oils.