Any of a class of organic or inorganic chemical compounds of silicon, oxygen, and usually carbon and hydrogen, based on the structural unit R2SiO, where R is an alkyl group, usually methyl.
[SIL(ICON) + OX(YGEN) + (METH)ANE.]
siloxane
Dictionary:
si·lox·ane (sĭ-lŏk'sān', sī-)  |
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| WordNet: siloxane |
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The noun has one meaning:
Meaning #1:
any of a large class of compounds that have alternate silicon and oxygen atoms
| Wikipedia: 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.
Siloxanes can have branched or unbranched backbones consisting of alternating silicon and oxygen atoms -Si-O-Si-O-, with side chains R attached to the silicon atoms.[1] More complicated structures are also known, for example eight silicon atoms at the corners of a cube, connected by 12 oxygen atoms as the cube edges.[2]
The word siloxane is derived from the words silicon, oxygen, and alkane.
Polymerized siloxanes with organic side chains (R ≠ H) are commonly known as silicones or as polysiloxanes. Representative examples are [SiO(CH3)2]n (polydimethylsiloxane) and [SiO(C6H5)2]n (polydiphenylsiloxane). These compounds can be viewed as a hybrid of both organic and inorganic compounds. The organic side chains confer hydrophobic properties while the -Si-O-Si-O- backbone is purely inorganic.
Contents |
Naming
M-units: (CH3)3SiO½, D-units: (CH3)2SiO, T-units: (CH3)SiO2
| Cyclic siloxanes | Linear siloxanes |
|---|---|
| D3: hexamethylcyclotrisiloxane | MM: hexamethyldisiloxane |
| D4: octamethylcyclotetrasiloxane | MDM: octamethyltrisiloxane |
| D5: decamethylcyclopentasiloxane | MD2M: decamethyltetrasiloxane |
| D6: dodecamethylcyclohexasiloxane | MDnM: polydimethylsiloxane |
Applications
Main article: Silicones
Siloxanes can be found in products such as cosmetics, deodorant, defoamers, water repelling windshield coating, food additives and some soaps. They occur in landfill gas and are being evaluated as alternatives to perchloroethylene for drycleaning. Perchloroethylene is widely considered environmentally undesirable.
Siloxanes in biogas
In internal combustion engines, siloxanes are oxidised to silicon dioxide which then forms deposits on pistons and cylinder heads which are extremely abrasive and cause damage to the internal components of the engine. Engines can require a complete overhaul at 5,000 h or less of operation. Deposits on the turbine of the turbocharger will eventually reduce the components efficiency.
Stirling engines are more resistant against siloxanes, though deposits on the tubes of the heat exchanger will reduce the efficiency.[3][4]
References
- ^ Siloxanes, IUPAC Gold Book
- ^ Stephen D. Kinrade, Jeffrey C. H. Donovan, Andrew S. Schach and Christopher T. G. Knight (2002), Two substituted cubic octameric silicate cages in aqueous solution. J. Chem. Soc., Dalton Trans., 1250 - 1252. DOI: 10.1039/b107758a
- ^ Presentation - Siloxanes in landfill gas
- ^ Paper - Siloxanes in landfill and digester gas
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Siloxane". Read more |
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- How is a contact lens made?
- Polyvinyl siloxane
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