Friction properties of vegetable oils

Vegetable oils are a renewable and an environmentally friendly alternative to petroleum-based oils in lubrication and other important application areas. Vegetable oils fall into two broad chemical categories: triesters (or TG) and monoesters. Most vegetable oils are triesters of glycerol with FA, whose characteristics are dependent on the chemistry and composition of the FA residues. A small percentage of vegetable oils are monoesters of long-chain FA and fatty alcohols of varying chemistries. In this work, the free energy of adsorption (DeltaG(ads)) of safflower (SA), high-oleic safflower (HOSA), and jojoba (JO), methyl oleate (MO), and methyl palmitate (MP) on steel were investigated. SA and HOSA are TG of vegetable oils with FA residues of radically different degrees of unsaturation. JO is a monoester vegetable oil. DeltaG(ads), is one of the major factors affecting the boundary friction properties of lubricant ingredients. DeltaG(ads) was found to increase in the order: HOSA less than or equal to SA < JO < MO less than or equal to MP. The results are consistent with the degree of functionality and other chemical properties of the oils studied.