Grease (lubricant)

A true grease consists of an oil or other fluid lubricant that is mixed with a thickener, typically a soap, to form a solid or semisolid.

After sufficient force to shear the grease has been applied, the viscosity drops and approaches that of the base lubricant, such as mineral oil.

EP greases have increased resistance to film breakdown, form sacrificial coatings on the metal surface to protect if the film does break down, or include solid lubricants such as graphite, molybdenum disulfide or hexagonal boron nitride (hBN) to provide protection even without any grease remaining.

[citation needed] Grease from the early Egyptian or Roman eras is thought to have been prepared by combining lime with olive oil.

For example, black slugs Arion ater were used as axle-grease to lubricate wooden axle-trees or carts in Sweden.

It categorizes greases suitable for the lubrication of chassis components and wheel bearings of vehicles, based on performance requirements, using codes adopted from the NLGI's “chassis and wheel bearing service classification system”: A given performance category may include greases of different consistencies.

Standard ISO 6743-9 “lubricants, industrial oils and related products (class L) — classification — part 9: family X (greases)”, first released in 1987 by the International Organization for Standardization, establishes a detailed classification of greases used for the lubrication of equipment, components of machines, vehicles, etc.

It assigns a single multi-part code to each grease based on its operational properties (including temperature range, effects of water, load, etc.)

Apiezon, silicone-based, and fluoroether-based greases are all used commonly in laboratories for lubricating stopcocks and ground glass joints.

The grease helps to prevent joints from "freezing", as well as ensuring high vacuum systems are properly sealed.

This quality makes clean-up with pentane or hexanes trivial, but also easily leads to contamination of reaction mixtures.

Food-grade lubricant base oil are generally low sulfur petrochemical, less easily oxidized and emulsified.

[citation needed] In some cases, the lubrication and high viscosity of a grease are desired in situations where non-toxic, non-oil based materials are required.

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