Submitted to: Proceedings JOCS/AOCS World Congress
Publication Type: Abstract only
Publication Acceptance Date: 10/27/2000
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Annual consumption of oil-based lubricants in the U.S. is close to 10 million metric tons valued at more than $8 billion. Major components in lubricants are basestock (usually 80% or more) and additives, which are used to enhance the most important properties, depending on application. Most of the basestocks originate from petroleum, including many synthetic esters and polyalphaolefins. Vegetable oil basestocks and other vegetable-based fluids have seen a quite promising increase in use as biodegradable lubricants over the last decade. However, still less than 2% of all basestocks are products of oleochemical and related industries. These basestocks are mostly used for hydraulic fluids. The most serious disadvantage of vegetable oils when used in lubricants is their poor oxidative stability. Bis-allylic hydrogen in methylene- interrupted polyunsaturated fatty acids is very susceptible to free radical attacks, peroxide formation and production of polar oxidation products. Oxidation results in increased acidity, corrosion, viscosity and volatility of the lubricant. Antioxidant additives improve oxidative stability of vegetable oils to only a limited extent and chemical modification is necessary to eliminate bis-allylic hydrogen. We conducted additional micro-oxidation experiments to identify the triglyceride ability to oxypolymerize into branched networks that may result in oxidative gelation and subsequent problems in filterability and flowability. We carried out extensive low temperature testing to show that vegetable oils solidify at -20C upon long-term exposure. Therefore, chemical modifications are necessary to suppress or eliminate triglyceride crystallization.