In October of last year, astronauts on the International Space Station were on a critical mission that required them to leave the safety of the orbiting laboratory and venture out into the void of space. Flight Engineer Mark Vande Hei from Falls Church, Virginia, headed out through the hatch bearing the specialized tool he would need to service the stations 58-foot robot arm: a grease gun.
Finding a lubricant that will work in the harsh environment of outer space is precisely the type of application that keeps chemists and engineers pushing the limit of lubricant technology and looking for innovations in the world of grease. Each advancement, when incorporated into a finished product, must work better than what came before.
Grease as Art
Finding the right formulation for the right job at the right price requires some creative thinking. Ruiming Ray Zhang of Vanderbilt Chemicals, based in Norwalk, Connecticut, said, Grease formulation is more of an art than an exact science. This is not to say there is no scientific guidance in formulating greases; rather, the best practice might be a give-and-take, a compromise between many factors instead of just one single target. Formulating grease is a balancing act.
The balancing act is defined by the three-part harmony of base oil, thickener and additives-the three components of grease. Most modern greases use mineral oil as a base, which accounts for 70 to 95 percent of the finished product. But if the grease needs to work in extreme temperatures, formulators may start with a synthetic fluid that offers better stability.
Although longer-life grease will normally need modern base oils derived from either synthetic fluids or highly refined mineral oils, the use of suitable antioxidants for these modern base oils is equally important, Zhang pointed out.
Additives comprise up to 10 percent of the grease and help enhance desirable properties while suppressing any undesirable side effects such as oxidation and friction.
While significant effort is focused on energy efficient engine oils, the importance of grease with lower frictional performance cannot be neglected. For many decades, Vanderbilts extensive organo-molybdenum additives have been used in grease formulations for friction reduction, said Zhang.
Thickeners can comprise anywhere from 3 to 30 percent of a grease, and they are what makes grease more solid than liquid. Popular thickeners include different types of metallic soaps, concocted from water insoluble salts made from a fatty acid and a metal, usually lead or aluminum. But the hot soap on the market now is lithium, due to its high dropping point and excellent load carrying abilities.
Lithium is an element that appears as a soft, silvery white alkali metal. Its reactive, flammable and easily corrodes in moist air. It does not occur freely in nature but can be found hiding in minerals and in seawater. Once freed, it is typically stored in mineral oil. Its the same stuff used to treat mental illness and was used to help create the worlds first fully man-made nuclear reaction.
The country of Chile has the worlds largest reserves and highest production of lithium. The grease industry must compete for these reserves against the batteries that power our phones, laptops, tablets and electric cars, of which there are more being made every year.
Fears of lithium shortages are worth panicking about-or should be ignored, depending on whom you listen to-but there is no denying the price of the illusive metal turned very sharply upward in 2015 and hasnt come back down to where it was in the early 2000s.
Innovating with Raw Materials
As lithium prices have become more volatile, chemists have broadened their search for innovative alternatives. Jim Vence is a technical director with Elco Corp., based in Cleveland, Ohio. He noted one approach to keeping grease production costs in check: There have been innovations in the process and materials used for lithium complex grease. Borates have been replacing diacid as raw materials. This allows a manufacturer to shorten the production time and cost.
Blending lithium is another innovation that may hold some promise. Weve also seen more lithium/calcium grease blends to lower cost and maintain the performance of lithium grease, said Vence.
The National Lubricating Grease Institute has chronicled the world of grease since 1933. On its website, the organization addresses a number of frequently asked questions about grease, including why there are so many types of grease with such a wide variation in price. Many greases are formulated to have specific properties unique to the application for which they are intended. Electric motors take one general type of grease, while flexible couplings require a very different type, and automotive wheel bearings require yet another type of grease.
Ever-expanding degrees of specialization are the driving force in grease innovation. Given the continued technological development in modern machinery, the demand on grease is shifting more towards higher performance, longer life and lower energy consumption, said Zhang.
Because grease is an international business, innovation can create global sized challenges. Chemists are sometimes tasked with tinkering with the ingredients to produce something that works globally. We receive base grease samples from all around the world, and the properties can vary significantly, Vence reported. Formulating an additive for grease can be very specific to the part of the world the grease comes from and what the grease application will be.
Customers Drive Forward
For formulators exploring the next frontier of lubricating greases, working with government entities, testing and research are all keys to success. But the engineers and chemists looking for grease innovation must also be attentive to their customers concerns.
We apply our resources according to the voice of the customer and identified market opportunities that offer sustainability. We will get requests to improve a specific property for specialized greases, such as longer wheel bearing life or higher 4-ball weld loads, whilst maintaining all other properties, said Vence.
Zhang observed, There are many factors to be considered in order to have a high-performance grease that will be superb for the particular application intended. If we refer to performance, cost and environment concerns as an older balancing act, the modern grease formulation will be a balancing act of higher performance, longer life and higher energy efficiency.