History of Greases

According to the historical accounts, it is said that as early as 2400 B.C. grease-like substance, oil and water were used as lubricant to reduce friction. In a painted wall relief of an Egyptian Pharaoh’s tomb dated to around 2400 B.C., a worker is seen pouring lubricant (in this case, water) for moving statues. Chariots from another Egyptian Pharaoh’s tomb dated to around 1400 B.C. are found with what seems an early form of grease derived from animal fat on the axle. While there are evidence showing the use of natural asphalt, most of the lubricating oil used in these times was based on animal or vegetable fat. It was only in modern times when grease formulated with petroleum, lubricating oil came into use. Calcium grease using mineral oil, animal fat and limestone was invented in the U.S in 1845. In the year 1938, lithium grease was invented and rapidly came into wide use as multi-purpose grease. The world’s first urea grease was invented in the U.S. in the year 1952.

Grease is a solid or semi-solid lubricant formed as a dispersion of thickening agents in a liquid lubricant. Lubricating greases can be considered to typically be a stable dispersion of a discontinuous phase in a continuous phase. This stable dispersion results in the non-Newtonian rheology that distinguishes a lubricating grease from a Newtonian fluid. The discontinuous phase is the thickener and is primarily responsible for that grease-like rheology. The continuous phase is the base oil (or blend of base oils). So, the greases generally consist of soap emulsified with mineral or vegetable oil. Although there are many ways to classify lubricating greases, the most common way is according to the thickener that is used. Grease thickeners can be broadly separated into two categories: soaps and non-soaps. Soap-based thickeners are generally the acid-base reaction products of a metal-containing base and an organic acid, usually a carboxylic acid. Soap thickeners can be further divided into simple soap and complex soap thickeners. Non-soap thickeners are usually formed by other types of chemical reactions or by incorporation of a solid entity.

A common feature of greases is that they possess a high initial viscosity, which upon the application of shear, drops to give the effect of an oil-lubricated bearing of approximately the same viscosity as the base oil used in the grease. This change in viscosity is called shear thinning. Grease is sometimes used to describe lubricating materials that are simply soft solids or high viscosity liquids, but these materials do not exhibit the shear-thinning properties characteristic of the classical grease. For example, petroleum jellies such as Vaseline are not generally classified as greases. Greases are applied to mechanisms that can be lubricated only infrequently and where a lubricating oil would not stay in position. They also act as sealants to prevent ingress of water and incompressible materials. Grease-lubricated bearings have greater frictional characteristics because of their high viscosity.

The demand for lithium has boomed in recent years, particularly with the global push towards electric vehicles (EVs). What was once an element with limited applications, lithium’s use in rechargeable batteries has caused an explosion in demand. Since 2021, the price of lithium carbonate has increased more than 400% and it continues to move up. The supply is not keeping up with demand, as the global shift to electric vehicles continues to push demand. Shortage of lithium has increased the cost of lithium greases exponentially. Now, every grease manufacturer is working on the improvement of non-lithium greases and establish their performance against most popular lithium grease. In near future there will be gradual shift in the demand of lithium greases and market shares of non-lithium greases will increase.