Silicone oil
Encyclopedia
A silicone oil is any polymerized siloxane
s with organic side chains. They are formed of alternating silicon-oxygen
atoms (...Si-O-Si-O-Si...) or siloxane
, rather than carbon atoms (...C-C-C-C...). Other species attach to the tetravalent silicon atoms, not to the divalent
oxygen atoms which are fully committed to forming the siloxane
chain. A typical example is polydimethylsiloxane
, where two methyl groups attach to each silicon atom to form (H3C)[Si(CH3)2O]nSi(CH3)3. The carbon analogue would be an alkane
, e.g. dimethylpropane
C5H12 or (H3C)[C(CH3)2](CH3).
. They are excellent electrical insulators and, unlike their carbon analogues, are non-flammable. Their temperature-stability and good heat-transfer characteristics make them widely used in laboratories for heating baths ("oil baths") placed on top of hotplate stirrers, as well as in freeze-dryers as refrigerant
s. Silicone oil is also commonly used as the working fluid in diffusion pump
s.
Some silicone oils, such as simethicone
, are potent anti-foaming agents due to their low surface tension
. They are used in industrial applications such as distillation
or fermentation
where excessive amounts of foam
can be problematic. They are sometimes added to cooking oils to prevent excessive frothing during deep frying
. Silicone oils used as lubricants can be inadvertent defoamers (contaminants) in processes where foam is desired, such as in the manufacture of polyurethane
foam. Silicone oil is also one of the two main ingredients in Silly Putty
, along with boric acid
.
s) often contain silicone oil. Silicone oils have been used as a vitreous fluid substitute to treat difficult cases of retinal detachment, such as those complicated with proliferative vitreoretinopathy, giant retinal tears, and penetrating ocular trauma.
assembly.
Siloxane
A siloxane is any chemical compound composed of units of the form R2SiO, where R is a hydrogen atom or a hydrocarbon group. They belong to the wider class of organosilicon compounds....
s with organic side chains. They are formed of alternating silicon-oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atoms (...Si-O-Si-O-Si...) or siloxane
Siloxane
A siloxane is any chemical compound composed of units of the form R2SiO, where R is a hydrogen atom or a hydrocarbon group. They belong to the wider class of organosilicon compounds....
, rather than carbon atoms (...C-C-C-C...). Other species attach to the tetravalent silicon atoms, not to the divalent
Divalent
In chemistry, a divalent ion or molecule has a valence of two and thus can form two bonds with other ions or molecules. An older term for divalent is bivalent....
oxygen atoms which are fully committed to forming the siloxane
Siloxane
A siloxane is any chemical compound composed of units of the form R2SiO, where R is a hydrogen atom or a hydrocarbon group. They belong to the wider class of organosilicon compounds....
chain. A typical example is polydimethylsiloxane
Polydimethylsiloxane
Polydimethylsiloxane belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological properties. PDMS is optically clear, and, in general, is...
, where two methyl groups attach to each silicon atom to form (H3C)[Si(CH3)2O]nSi(CH3)3. The carbon analogue would be an alkane
Alkane
Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...
, e.g. dimethylpropane
Neopentane
Neopentane, also called dimethylpropane, is a double-branched-chain alkane with five carbon atoms. Neopentane is an extremely flammable gas at room temperature and pressure which can condense into a highly volatile liquid on a cold day, in an ice bath, or when compressed to a higher...
C5H12 or (H3C)[C(CH3)2](CH3).
Applications
Silicone oils are primarily used as lubricants or hydraulic fluidsHydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...
. They are excellent electrical insulators and, unlike their carbon analogues, are non-flammable. Their temperature-stability and good heat-transfer characteristics make them widely used in laboratories for heating baths ("oil baths") placed on top of hotplate stirrers, as well as in freeze-dryers as refrigerant
Refrigerant
A refrigerant is a substance used in a heat cycle usually including, for enhanced efficiency, a reversible phase change from a liquid to a gas. Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as refrigerants, but they are being phased out because of their ozone depletion...
s. Silicone oil is also commonly used as the working fluid in diffusion pump
Diffusion pump
Diffusion pumps use a high speed jet of vapor to direct gas molecules in the pump throat down into the bottom of the pump and out the exhaust. Presented in 1915 by Wolfgang Gaede and using mercury vapor, they were the first type of high vacuum pumps operating in the regime of free molecular flow,...
s.
Some silicone oils, such as simethicone
Simethicone
Simethicone is an oral anti-foaming agent used to reduce bloating, discomfort and pain caused by excess gas in the stomach or intestinal tract. It is a mixture of polydimethylsiloxane and silica gel.-Chemical action and pharmaceutical effects:...
, are potent anti-foaming agents due to their low surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
. They are used in industrial applications such as distillation
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
or fermentation
Industrial fermentation
Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.- Food fermentation :...
where excessive amounts of foam
Foam
-Definition:A foam is a substance that is formed by trapping gas in a liquid or solid in a divided form, i.e. by forming gas regions inside liquid regions, leading to different kinds of dispersed media...
can be problematic. They are sometimes added to cooking oils to prevent excessive frothing during deep frying
Deep frying
Deep frying is a cooking method in which food is submerged in hot oil or fat. This is normally performed with a deep fryer or chip pan; industrially, a pressure fryer or vacuum fryer may be used....
. Silicone oils used as lubricants can be inadvertent defoamers (contaminants) in processes where foam is desired, such as in the manufacture of polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
foam. Silicone oil is also one of the two main ingredients in Silly Putty
Silly Putty
Silly Putty , is the Crayola-owned trademark name for a class of silicone polymers. It is marketed today as a toy for children, but was originally created by accident during research into potential rubber substitutes for use by the United States in World War II...
, along with boric acid
Boric acid
Boric acid, also called hydrogen borate or boracic acid or orthoboric acid or acidum boricum, is a weak acid of boron often used as an antiseptic, insecticide, flame retardant, as a neutron absorber, and as a precursor of other chemical compounds. It exists in the form of colorless crystals or a...
.
Medical uses
Consumer products to control flatus (antiflatulentAntiflatulent
An antiflatulent agent is a drug used for the alleviation or prevention of excessive intestinal gas, i.e., flatulence.- Preventing gas :* Enzymes - Enzyme-based dietary supplements break down indigestible substances and prevent these substances from reaching the large intestine intact -- where...
s) often contain silicone oil. Silicone oils have been used as a vitreous fluid substitute to treat difficult cases of retinal detachment, such as those complicated with proliferative vitreoretinopathy, giant retinal tears, and penetrating ocular trauma.
Automotive use
Silicone oil is commonly used as the fluid in the automobile cooling fan clutchFan clutch
A fan clutch is a thermostatic device that exists as an integral component of certain automotive cooling systems. When the engine is cool or even at normal operating temperature, the fan clutch partially disengages the engine's mechanically-driven radiator cooling fan, generally located at the...
assembly.