Vegetable oil-based lubricants come full circle
Vegetable oils have been used as lubricants for thousands of years since originating in ancient civilisations like Mesopotamia (modern-day Iraq) and Egypt. Humans discovered that certain natural fats and oils possessed unique properties that reduced friction and provided a smooth surface for various mechanical devices.
In the 20th century, there was a significant shift in lubrication. The emergence of mineral oils, derived from petroleum, answered mechanical needs around oxidative stability and initiated a gradual replacement of natural fats. During World War II, Germany led developments in synthetic chemistries, due to a scarcity of natural resources and the need for advanced lubricants.
Now, confronted by global warming, we appear to have come full circle. There is renewed interest in vegetable oil chemistries, says Dr. Selim M. Erhan, director of business development, Process Oils Inc., an Ergon company. Speaking during F+L Week 2023, held in Kuala Lumpur, Malaysia, from June 14-16, Erhan outlined significant advances in sustainable vegetable oil chemistries for use in high-performance applications.
Erhan started his career with the U.S. Department of Agriculture (USDA) after obtaining his Ph.D. in Organic-Polymer Chemistry from Western Michigan University. At USDA, he worked on finding industrial applications for vegetable oils in areas such as rubber, paper, agricultural sprays, pharmaceuticals, food, lubricant, and oil field applications. He then moved to the private sector, including D. A. Stuart Company, Georgia Pacific, Polartech, Afton Chemical, Elevance Renewable Sciences and Archer Daniels Midland Company (ADM), where he was global commercial development manager for Industrial Oils. Erhan has worked on industrial applications for vegetable oils for the past 10 years, including formulating finished fluids and emulsifying packages. He joined Process Oils in 2020.
New technologies are creating challenges for formulators. Stringent fuel efficiency requirements require lighter, stronger metals. This demands better lubricants for tougher machining, says Erhan.
Erhan also outlined complications around the formulation of polymers, the phase-out of medium-chain chlorinated paraffins and difficulties with long-chain chlorinated paraffins. There is a need for more neutral base oils—but with solvency, and fuels require more lubricity with the removal of sulphur. Formulators are also mindful of lowering their carbon footprint, he adds.
We are entering a new era, says Erhan, emphasising the importance of higher-performance chemistries that address these changing technology needs. Bridging the two worlds of mineral oils and vegetable oils can create interesting synergies, says Erhan. Ergon has worked with a variety of different sources including Group II, Group III, naphthenic and vegetable oils in a large portfolio of base oil applications.
During F+L Week, Erhan outlined several advantages of vegetable oil derivatives. We can manipulate the natural resources to remove the negative aspects, which are mainly oxidative stability, says Erhan. One example is Ergon’s Aurora plant-based oils, which have been further processed to eliminate several handicaps such as poor oxidative and hydrolytic stability. Their performance is close to that of mineral oil. Molecular weight, size and acid value can be adjusted in production.
The discussion focused primarily on the benefits of vegetable oils as extreme pressure (EP) lubricity additives. Triglycerides contain three fatty acids with different lengths or patterns of carbon chain double bonds—which are prone to oxidation. However, we can react the double bonds and remove them, says Erhan. This enables cross-linking and the creation of products with different capabilities. Cross-linking allows technicians to start growing molecules in three dimensions. Large, spherical cross-linked molecules have a lot of advantages—mainly in film thickness, he says.
The plant-based oils do not rely on the chemistry of the surface, working similarly on steel, aluminium, titanium, magnesium and copper. Being immune to the metallurgy of the surface is a “big deal” as formulators want to create one fluid that can address a variety of different metals, says Erhan. The oils function equally well without the issues of phosphorus and sulphur and the need for heat activation. The moment it touches the surface it starts working, he says.
Nowadays, fluids are being pushed at very high pressures. A lot of modern machines are running enclosed systems—where everything is measured with optical eyes. Foaming is a significant issue, as it can block Computer Numerical Control (CNC) optical eyes. The large molecule size reduces foaming because they break the foam membranes, says Erhan. Wherever there are vegetable oils, you can have these types of molecules.
Vegetable oil derivatives can be used as high-performing additives that are bio-based, renewable and globally available. Erhan noted that these chemistries are associated with lower costs, due to a reduction in the number of manufacturing steps. Specific applications include lubricity additives, marine oils and fuel additives.
The most pressing question for manufacturers is whether high molecular weights can be formulated effectively. Typically, large, long-chain molecules are difficult to formulate and emulsify. However, Erhan indicated that these molecules are more compact, with their spherical shape aiding formulation. These renewable chemicals can answer some of the most difficult issues today and in the future, says Erhan.