Grease is a lubricant of higher initial viscosity than oil, consisting originally of a calcium, sodium or lithium soap jelly emulsified with mineral oil. A lubricant (colloquially, lube, although this usually refers to personal lubricants) is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction and wear between them. ... The pitch drop experiment at the University of Queensland. ... Oil is a generic term for organic liquids that are not miscible with water. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/gray Atomic mass 6. ... SOAP is a protocol for exchanging XML-based messages over a computer network, normally using HTTP. SOAP forms the foundation layer of the web services stack, providing a basic messaging framework that more abstract layers can build on. ... A. Two immisicble liquids, not emulsified; B. An emulsion of Phase B dispersed in Phase A; C. The unstable emulsion progressively separates; D. The (purple) surfactant positions itself on the interfaces between Phase A and Phase B, stabilizing the emulsion An emulsion is a mixture of two immiscible (unblendable) substances. ... Mineral oil or liquid petrolatum is a by-product in the distillation of petroleum to produce gasoline. ...

Properties of grease

Greases are a type of shear-thinning or pseudo-plastic fluid, which means that the viscosity of the fluid is reduced under shear. After sufficient force to shear the grease has been applied, the viscosity drops and approaches that of the base mineral oil (or that of the EP additive for EP greases under heavy load). This sudden drop in shear force means that grease is considered a plastic fluid, and the reduction of shear force with time makes it thixotropic. It is often applied using a grease gun. A Power-law fluid is an idealized fluid for which the shear stress, τ, is given by where: K is the flow consistency index (SI units Pa•sn), ∂u/∂y is the shear rate or the velocity gradient perpendicular to the plane of shear (SI unit s-1), and n... A subset of the phases of matter, fluids include liquids, gases, plasmas and, to some extent, plastic solids. ... The pitch drop experiment at the University of Queensland. ... In physics and mechanics, shear refers to a deformation that causes parallel surfaces to slide past one another (as opposed to compression and tension, which cause parallel surfaces to move towards or away from one another). ... Thixotropy is the property of some non-newtonian pseudoplastic fluids to show a time dependant change in viscosity; the longer the fluid undergoes shear, the lower its viscosity. ... A grease gun is a common workshop and garage tool used for lubrication. ...

Uses for grease

Greases are employed where heavy pressures exist, where oil drip from the bearings is undesirable, and/or where the motions of the contacting surfaces are discontinuous so that it is difficult to maintain a separating lubricant film in the bearing. Grease-lubricated bearings have greater frictional characteristics at the beginning of operation. Under shear, the viscosity drops to give the effect of an oil-lubricated bearing of approximately the same viscosity as the base oil used in the grease. Calcium- and sodium-based greases are the most commonly used; sodium-based greases have higher melting point than calcium-based greases but are not resistant to the action of water. Lithium-based grease has a drip temperature at 350° to 400°F and it resists moisture, hence it is commonly used as lubricant in household products such as garage door openers. Pressure(symbol: p) is the forceper unit areaacting on a surface in a direction perpendicularto that surface. ... A bearing is a component used to reduce friction in a machine. ... Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. ... A girl in a swimming pool full of water Water (from the Old English word waeter; c. ...

Grease additives

Teflon is added to some greases to improve their lubricating properties. Gear greases consist of rosin oil, thickened with lime and mixed with mineral oil, with some percentage of water. Special-purpose greases contain glycerol and sorbitan esters. They are used, for example, in low-temperature conditions. Some greases are labeled "EP", which indicates "extreme pressure". Under high pressure or shock loading, normal grease can be compressed to the extent that the greased parts come into physical contact, causing friction and wear. EP grease contains solid lubricants, usually graphite and/or molybdenum, to provide protection under heavy loadings. The solid lubricants bond to the surface of the metal, and prevent metal-to-metal contact and the resulting friction and wear when the lubricant film gets too thin. Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910–1994) of DuPont in 1938 and introduced as a commercial product in 1946. ... Rosin is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vapourise the volatile liquid terpene components. ... Calcium oxide (CaO), commonly known as lime, quicklime or burnt lime, is a widely used chemical compound. ... ... Graphite (named by Abraham Gottlob Werner in 1789, from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ... General Name, Symbol, Number molybdenum, Mo, 42 Chemical series transition metals Group, Period, Block 6, 5, d Appearance gray metallic Atomic mass 95. ...

Other greases

Other types of lubricating material that are soft solids at room temperature are often called grease, though they may not exhibit the shear-thinning properties typical of the oil/soap grease. Silicone grease is an amorphous fumed, silica-thickened, polysiloxane-based compound, which can be used to provide lubrication and corrosion resistance. Since it is not oil-based, it is often used where oil-based lubricants would attack rubber seals. Silicone greases also maintain stability under high temperatures, and are often used, in pure form or mixed with zinc oxide, to join heat sinks to computer CPUs. Petroleum jellies, such as Vaseline, are also sometimes called greases, and are commonly used for lubricating food-handling equipment. Silicones, or polysiloxanes, are inorganic polymers consisting of a silicon-oxygen backbone (...-Si-O-Si-O-Si-O-...) with side groups attached to the silicon atoms. ... Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. ... Zinc oxide is a chemical compound with formula ZnO. It is nearly insoluble in water but soluble in acids or alkalis. ... A large copper heatsink. ... A computer is a machine for manipulating data according to a list of instructions - a program. ... Intel 80486DX2 microprocessor in a ceramic PGA package A central processing unit (CPU), or sometimes simply processor, is the component in a digital computer that interprets instructions and processes data contained in software. ... Petroleum jelly or petrolatum is made by refining a byproduct of oil drilling. ... Petroleum jelly or petrolatum is a byproduct of the refining of petroleum, made from the residue of petroleum distillation left in the still after all the oil has been vaporized. ...

External links

• University of Northern Iowa's Agriculture-Based Industrial Lubricants Grease Application Guide (google.com cached copy)
• U.S. Army Corps of Engineers grease definition and application guide (PDF file)
• Silicone grease (includes link to MSDS and application guide)

See also

Dropping point Dropping Point is a qualitative property of a lubricating grease that gives a general indication of the temperature at which a grease passes from a semi-solid to liquid state under specific test conditions. ...