Lubricants

Lubricants are an essential part of modern machinery. Everything from computer hard disk drives to the Airbus A380 requires lubrication of its moving parts. more...

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A lubricant (colloquially, lube, although this may also refer to personal lubricants) is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction and wear between them. A lubricant provides a protective film which allows for two touching surfaces to be separated, thus lessening the friction between them.

Typically lubricants contain 90% base oil (most often petroleum fractions, called mineral oils) and less than 10% additives. Vegetable oils or synthetic liquids such as hydrogenated polyolefins, esters, silicone, fluorocarbons and many others are sometimes used as base oils. Additives deliver reduced friction and wear, increased viscosity, improved viscosity index, resistance to corrosion and oxidation, aging or contamination, etc.

Non-liquid lubricants include grease, powders (dry graphite, PTFE, Molybdenum disulfide, etc.), teflon tape used in plumbing, air cushion and others. Another approach to reducing friction and wear is to use bearings such as ball bearings, roller bearings or air bearings or to use sound, in the case of acoustic lubrication.

Lubricants such as 2-cycle oil are also added to some fuels. Sulfur impurities in fuels also provide some lubrication properties, which has to be taken in account when switching to a low-sulfur diesel; biodiesel is a popular diesel fuel additive providing additional lubricity.

In addition to automotive and industrial applications, lubricants are used for many other purposes, including K-Y Jelly, often used as a personal lubricant, bio-medical applications (e.g. lubricants for artificial joints) and others.

Purpose

Lubricants perform the following key functions.

Keep moving parts apart; Reduce friction; Transfer heat; Carry away contaminants & debris; Transmit power; Protect against wear; Prevent corrosion;

History

Romans used rags dipped in animal fat to lubricate wagon wheels; however the science of lubrication (tribology) really only took off with the industrial revolution in the nineteenth century.

General composition

Lubricants are generally composed of a majority of base oil and a minority of additives to impart desirable characteristics.

Types of lubricants

Liquid including emulsions and suspensions; Solid; Greases; Pastes;

Liquid lubricants

Liquid lubricants may be characterized in many different ways. One of the most common ways is by the type of base oil used. Following are the most common types.

Read more at Wikipedia.org