Environmentally friendly functional fluids from renewable and sustainable sources-A review

Use of animal and plant based oils for lubrication dates back to history. Discovery of petroleum and subsequent improvements in the refining technologies replaced them with mineral oil based lubricants. Mineral oil is a fast depleting resource and is also considered as an environmental pollutant. Impact of mineral oil based lubricants and restrictive environmental regulations have increased interest in lubricants derived from natural resources. Vegetable oils being renewable, non-toxic and biodegradable have become the primary choice for environmentally sensitive and total loss lubricant applications ranging from hydraulic oils to grease. This study covers the technical viabilities associated with vegetable oil based lubricants in different applications. In the first part of this review eco labeling, environmental regulations, source, composition and availability of vegetable oils are discussed. In the later part of review, performance evaluation of vegetable oils in different applications is covered. It has been noticed that straight vegetable oils have performed satisfactorily in metal forming; metal working, hydraulic applications and have shown promising performance as greases and engine oils. It was also observed that the selection of lubricant is based on price, then on performance, and lastly on environmental consideration. This would change only with the legislative pressure on restricting the use of petroleum based products and economic incentives for biobased lubricants in environmentally sensitive applications.