Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/22/2005
Publication Date: 7/1/2005
Citation: Biresaw, G. 2005. Adsorption of amphphiles at an oil-water vs. oil-metal interface. Journal of the American Oil Chemists' Society. 82(4):285-292. Interpretive Summary: Increasing the demand for agricultural products requires development of new consumer and industrial products from farm-based raw materials. Another method is by using farm-based raw materials to replace petroleum-based components in existing products. An important area of application for farm-based products is in lubrication, which is currently dominated by petroleum-based products. Farm products can be developed into value-added components for lubricants used in various applications including metalworking, hydraulics, motor oil, etc. However, successful development of such products requires a thorough understanding of the lubrication properties of farm-based raw materials and their derivatives. In this work, a simplified and inexpensive procedure for studying the boundary lubrication properties of vegetable oils was investigated. The result indicates that the new method is capable of providing comparable results to rather expensive methods currently in use.
Technical Abstract: Studies were conducted to investigate if adsorption of amphiphiles from oil onto a degreased metal can be predicted from adsorption of the amphiphiles at the oil-water interface. The surface of a degreased metal comprises oxides, hydroxides, and adsorbed water vapor formed from reaction of the metal with air and moisture. Similarity, if any, between the water-oil and metal-oil interfaces is of interest in the development of a cheaper and quicker method of estimating the adsorption properties of amphiphiles on degreased metals. The amphiphiles used in this investigation were safflower (SA) and jojoba (JO), both of which are plant-based oils, and methyl palmitate (MP). SA is triester while JO and MP are monoesters. The interfacial tension of water-hexadecane was measured as a function of amphiphile concentration in hexadecane, and used to estimate an interfacial-based free energy of adsorption, deltaGads. The resulting interfacial-based deltaGads values for SA were identical to that reported from friction-based adsorption isotherms. The corresponding values for the monoesters were within the range reported from friction-based adsorption isotherms. The fact that the two methods predicted similar deltaGads values for triester and monoester amphiphiles provides the incentive to further investigate the interfacial method.