Chemical and Physical Properties of Inert Lubricants

Inert lubricants include three basic categories: oils, greases, and waxes. The main difference between each of the three types is their level of viscosity, with oils being the least viscous of the lubricants, and waxes being the most viscous.

The viscosity of inert lubricants is one important factor that determines how they are used in industry. This factor is actually relatively easy to control in the synthesis of inert lubricants, as the length of lubricant molecule chains determines their viscosity. The longer the chain, the more viscous the lubricant will be.

Most halocarbon oils are made up of molecules comprised of a single of repeating chemical motifs, with the viscosity being dependent on the length of the chain. This means that to increase the viscosity of a given inert lubricant, it is often simply a matter of synthesizing the molecule with extra repeats of the chemical motif that comprises its molecular ‘backbone' structure.

All three types of lubricant tend to be immiscible with water, and as they are inert, they are also non-reactive in most situations. Depending on the exact nature of the lubricant, it may or may not be miscible in solutions of ketones, alcohols, mineral oils, or other organic solvents. This means it's possible, by carefully choosing the structure of the inert lubricant molecule, to create an inert lubricant with just the right viscosity, which is miscible with whatever specific liquid chemicals are desired.

The property of being inert is of course the most desirable of the chemical properties of these oils, waxes, and greases: this is, in fact, why they are made. Inert lubricants are non-corrosive, non-flammable, have little toxicity, and provide good lubricity. Inert lubricants do not react to highly oxidative substances such as fluorine, acids, and oxygen, and remain stable at high temperatures. These properties make them highly useful for many industrial purposes.

Uses of Inert Lubricants

Inert lubricants are most often used to provide lubrication, but they can also be used as industrial solvents, non-flammable bath fluids (suitable for use at low as well as high temperatures), plasticizers for fluorinated products, metal-working fluid for work with metals such as tungsten, molybdenum, and tantalum, and as a safe, high-density and non-reactive fluid for laboratory tests. Inert lubricants are used in industries and processes as diverse as the pulp paper industry, where they are used in bleaching wood pulp, to the treatment of drinking water with fluorine and chlorine.

Oils: Inert oils are very heavily used in automotive industries, including the aeronautic, aviation, and marine industries in addition to traditional automotives. They may be used as engine oils, transmission fluid, gearbox fluid, brake fluids, and hydraulic fluids, or in fact in any piece of equipment or machinery that has moving parts that may be subject to high heat and friction. In other industries, inert oils may be used in steam and gas turbines, motors, air and gas compressors, and bearing and circulating systems. Again, any machine with moving parts is subject to increased wear and tear without the use of a lubricant, and inert lubricants are needed to reduce reactivity.

Greases: These are traditionally comprised of a jelly that is emulsified with mineral oil (which is itself an inert lubricant), to produce an inert lubricant with a much higher viscosity than that of oil. Greases are often more solid than liquid, and thus have an entirely different set of uses in comparison to many oils. While greases are often used for industrial purposes, to prevent the wear and tear caused by metal-to-metal contact in machinery and equipment, many types of inert greases are used in places such as laboratories, where chemically inert lubricants are particularly important for preventing reactions between lubricants and experimental substances.

Waxes: Inert waxes tend to be used as protective coatings or barriers, often designed to either keep moisture out, or to reduce friction between two moving parts (as in the case of skiers and their skis). Often they are used to protect a finished product from the oxidative effects of chlorine or oxygen, or simply to act as a water-barrier. In the metals industry, inert waxes are also often used as a friction-reducing lubricant.