Vacuum grease is a

lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...

with low volatility and is used for applications in low pressure environments. Lubricants with higher volatility would evaporate, causing two problems: * They would not be present to provide lubrication. * They would make lowering the pressure below their vapor pressure difficult. As well as a lubricant, vacuum grease is also used as a sealant for joints in

vacuum system Vacuum engineering deals with technological processes and equipment that use vacuum to achieve better results than those run under atmospheric pressure. The most widespread applications of vacuum technology are: * Pyrolytic chromium carbide coating ...

s. This is usually limited to soft vacuums, as

ultra high vacuum Ultra-high vacuum (UHV) is the vacuum regime characterised by pressures lower than about . UHV conditions are created by pumping the gas out of a UHV chamber. At these low pressures the mean free path of a gas molecule is greater than approximately ...

or high temperatures may give problems with the grease

outgassing Outgassing (sometimes called offgassing, particularly when in reference to indoor air quality) is the release of a gas that was dissolved, trapped, frozen, or absorbed in some material. Outgassing can include sublimation and evaporation (which a ...

. Grease is most commonly used with glass vacuum systems. All metal systems usually use knife-edge seals in soft metals instead. Where

O ring An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more par ...

seals are used, these should ''not'' be greased (in static seals at least) as it can cause the O rings to become permanently distorted when compressed., p. 115 In electronics manufacturing processes, vacuum grease is often used to prevent corrosion. One of the early vacuum greases is the

Ramsay grease Ramsay grease is a vacuum grease, used as a lubrication and a sealant of ground glass joints and cocks on laboratory glassware, e.g. burettes. It is usable to about 10−2 mbar (about 1 Pa) and about 30 °C. Its vapor pressure at 20 °C is ...

Examples

Perfluoropolyether Perfluoropolyether (PFPE) is a type of liquid lubricant that has been used in the aerospace industry for over 30 years. The main properties of PFPE are being temperature resistant between and (depending on specific composites), having very low ou ...

References

Grease Lubricants {{Material-stub