Submitted to: Surfactants in Tribology
Publication Type: Book / Chapter
Publication Acceptance Date: July 5, 2007
Publication Date: June 4, 2008
Citation: Biresaw, G. 2008. Tribological properties of ag-based amphphiles. In: Biresaw, G., Mittal, K.L., editors. Surfactants in Tribology. 1st edition. Boca Raton, FL: Taylor & Francis. p. 259-290.
Interpretive Summary: Currently, in the United States, there is a large quantity of surplus crops relative to market demand. This has suppressed prices and, hence, the income of farmers growing soybean, corn, wheat and other crops. One way of increasing demand for agricultural products, and thereby improving the income of farmers, is to develop methods for converting farm products into competitive consumer and industrial materials. Accomplishing this, however, will require developing a thorough understanding of the chemical/physical properties of farm-based raw materials. Also required is developing new methods to modify farm-products as needed, to attain competitive performance relative to petroleum-based products currently in the market. In the work described here, the properties of vegetable oils from various crops are explored for lubrication and other applications. Different techniques were employed to understand how vegetable oils modify surface properties for various applications. Knowledge from such investigations are essential for developing techniques for producing new products from surplus crops.
Most ag-based materials are amphiphilic because they comprise polar and non-polar groups within the same molecule. One of the major categories of amphiphilic ag-based materials are seed oils, which are actively investigated as substitutes for petroleum in a wide variety of consumer and industrial applications. Due to their amphiphilicity, seed oils adsorb on surfaces and alter various surface and interfacial properties. The adsorption properties of seed oils at metal-metal, starch-metal, hexadecane-water interfaces were investigated as a function of seed oil chemical structure, seed oil concentration, and substrate surface properties. The effect of vegetable oil adsorption on surface properties was monitored using interfacial tension and boundary friction measurements. The data was then analyzed using various adsorption models to estimate the free energies of adsorption of the vegetable oils as a function of vegetable oil and substrate characteristics. The result showed that the estimated free energies of adsorptions were independent of the method used to probe the adsorption of the vegetable oil at the interface (interfacial tension vs. boundary friction). However, the estimated free energies of adsorption were found to be functions of vegetable oil chemical structures, substrate surface properties, and the adsorption model used to analyze the adsorption data.