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Encyclopedia > Silicone

Silicones are largely inert compounds with a wide variety of forms and uses. Typically heat-resistant, nonstick and rubberlike, they are frequently used in cookware, medical applications, sealants, lubricants and insulation. Not to be confused with Silicone. ... Image File history File links Question_book-3. ... Image File history File links Mergefrom. ... Silicone rubber is a polymer that has a backbone of silicon oxygen linkages, the same bond that is found in quartz, glass and sand. ... This does not cite any references or sources. ... cast-iron iron enamel stainless steel The cooking pan is a type of food preparation utensil commonly found in the kitchen which includes many more specific cooking vessels such as saucepans and frying pans (or fry pans). ... For the chemical substances known as medicines, see medication. ... Self-leveling silicone firestop system used around pipe through-penetration in a two-hour fire-resistance rated concrete floor assembly. ... A lubricant (colloquially, lube) is a substance (often a liquid) introduced between two moving surfaces to reduce the friction and wear between them. ... Look up insulation in Wiktionary, the free dictionary. ...

1/2" thickness of silicone firestop sealant being successfully tested to hold a 6-foot head of water to prove water-resistance in new construction applications.
1/2" thickness of silicone firestop sealant being successfully tested to hold a 6-foot head of water to prove water-resistance in new construction applications.

Contents

Firestop after fire exposure during fire test in Tulsa, Oklahoma. ...

Properties

Some of the most useful properties of silicone include:

  1. Thermal stability (constancy of properties over a wide operating range of −100 to 250 °C).
  2. Though not lipophilic, the ability to repel water and form watertight seals.
  3. Excellent resistance to oxygen, ozone and sunlight.
  4. Flexibility.
  5. Good electrical insulation.
  6. Nonstick.
  7. Low chemical reactivity.
  8. Low toxicity.
  9. High gas permeability: at room temperature (25 °C) the permeability of silicone rubber for gases like oxygen is approximately 400 times that of butyl rubber, making silicone useful for medical applications (though precluding it from applications where gas-tight seals are necessary).

This article or section does not cite its references or sources. ...

Technical details

More precisely called polymerized siloxanes or polysiloxanes, silicones are mixed inorganic-organic polymers with the chemical formula [R2SiO]n, where R = organic groups such as methyl, ethyl, and phenyl. These materials consist of an inorganic silicon-oxygen backbone (…-Si-O-Si-O-Si-O-…) with organic side groups attached to the silicon atoms, which are four-coordinate. Image File history File links Broom_icon. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... Siloxanes are a class of both organic and inorganic chemical compounds which consist entirely of silicon, oxygen, and an alkyl group. ... Traditionally, inorganic compounds are considered to be of mineral, not biological, origin. ... Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... In chemistry a methyl-group is a hydrophobic Alkyl functional group which is derived from methane (CH4). ... Ethyl is a two-carbon substituent in organic chemistry. ... In chemistry, the phenyl group or phenyl ring (often abbreviated as -Ph) is the functional group with the formula -C6H5 Picture where the six carbon atoms are arranged in a cyclic manner. ... Not to be confused with Silicone. ... This article is about the chemical element and its most stable form, or dioxygen. ...


In some cases organic side groups can be used to link two or more of these -Si-O- backbones together. By varying the -Si-O- chain lengths, side groups, and crosslinking, silicones can be synthesized with a wide variety of properties and compositions. They can vary in consistency from liquid to gel to rubber to hard plastic. The most common siloxane is linear polydimethylsiloxane (PDMS), a silicone oil. The second largest group of silicone materials is based on silicone resins, which are formed by branched and cage-like oligosiloxanes. Vulcanization is an example of cross-linking. ... Polydimethylsiloxane (PDMS) is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological (or flow) properties. ... Silicone oils (polymerized siloxanes) are silicon analogues of carbon based organic compounds, and can form (relatively) long and complex molecules based on silicon rather than carbon. ... Silicone resins is a type of silicone material which is formed by branched, and cage-like oligosiloxanes with the general formula of RnSiXmOy, where R is a non reactive substituent, usually Me or Ph, and X is a functional group H, OH, Cl or OR. These groups are further condensed...


Synthesis

Silicones are synthesized from chlorosilanes, tetraethoxysilane, and related compounds. In the case of PDMS, the starting material is dimethylchlorosilane, which reacts with water as follows: Chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. ... Tetraethyl orthosilicate is the major chemical compound with the formula Si(OC2H5)4. ... Chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

n [Si(CH3)2Cl2] + n [H2O] → [Si(CH3)2O]n + 2n HCl

During polymerization, this reaction evolves potentially hazardous hydrogen chloride gas. For medical uses, a process was developed where the chlorine atoms in the silane precursor were replaced with acetate groups, so that the reaction product of the final curing process is nontoxic acetic acid (vinegar). As a side effect, the curing process is also much slower in this case. This is the chemistry used in many consumer applications, such as silicone caulk and adhesives. An example of alkene polymerisation, in which each Styrene monomer units double bond reforms as a single bond with another styrene monomer and forms polystyrene. ... R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... R-phrases , S-phrases , , , Flash point 43 °C Related Compounds Related carboxylic; acids Formic acid; Propionic acid; Butyric acid Related compounds acetamide; ethyl acetate; acetyl chloride; acetic anhydride; acetonitrile; acetaldehyde; ethanol; thioacetic acid; acetylcholine; acetylcholinesterase Supplementary data page Structure and properties n, εr, etc. ... For a description of caulking in computer game creation, refer to caulking (computer games) Caulking is a process used in the sealing of the seams in wooden boats and making them watertight. ... For the band, see Adhesive (band). ...


Silane precursors with more acid-forming groups and fewer methyl groups, such as methyltrichlorosilane, can be used to introduce branches or cross-links in the polymer chain. Ideally, each molecule of such a compound becomes a branch point. This can be used to produce hard silicone resins. Similarly, precursors with three methyl groups can be used to limit molecular weight, since each such molecule has only one reactive site and so forms the end of a siloxane chain. Vulcanization is an example of cross-linking. ... Silicone resins is a type of silicone material which is formed by branched, and cage-like oligosiloxanes with the general formula of RnSiXmOy, where R is a non reactive substituent, usually Me or Ph, and X is a functional group H, OH, Cl or OR. These groups are further condensed...


Modern silicone resins are made with tetraethoxysilane, which reacts in a more mild and controllable manner than chlorosilanes. Tetraethyl orthosilicate is the major chemical compound with the formula Si(OC2H5)4. ...


Chemical terminology

Silicone is often mistakenly referred to as "silicon." Although silicones contain silicon atoms, they are not made up exclusively of silicon, and have completely different physical characteristics from elemental silicon. Not to be confused with Silicone. ...


The word "silicone" is derived from ketone. Dimethylsilicone and dimethyl ketone (a.k.a. acetone) have analogous formulas, thus it was surmised (incorrectly) that they have analogous structures. The same terminology is used for compounds such as silane (an analogue of methane). Ketone group A ketone (pronounced as key tone) is either the functional group characterized by a carbonyl group (O=C) linked to two other carbon atoms or a chemical compound that contains this functional group. ... For other uses, see Acetone (disambiguation). ... Silane is a chemical compound with chemical formula SiH4. ... Methane is a chemical compound with the molecular formula . ...


A true silicone group with a double bond between oxygen and silicon (see figure) does not exist in nature; chemists find that the silicon atom forms a single bond with each of two oxygen atoms, rather than a double bond to a single atom. Polysiloxanes are called "silicone" due to early mistaken assumptions about their structure.


Uses

Aquarium joints

Aquarium manufacturers have used silicone sealant exclusively from its inception in order to join glass plates, making aquariums of every size and shape. Glass joints made with silicone sealant can withstand hundreds of metric tons of pressure, making obsolete the original aquarium construction method using angle-iron and putty.


Automotive

In the automotive field, silicone grease is typically used as a lubricant for brake components since it is stable at high temperatures, is not water-soluble and is far less likely than other lubricants to foul. This article is about the vehicle component. ...


Automotive spark plug wires are often insulated by multiple layers of silicone to prevent sparks from jumping to adjacent wires, causing misfires. The insulation also minimizes RFI, which can interfere with an engine management computer. RFI can mean: Radio Frequency Interference or electromagnetic interference Radio France Internationale Request For Information, a business process Requirement for Improvement, a citation from Joint Commission on Accreditation of Healthcare Organizations Return From Interrupt, a PowerPC machine instruction Rete Ferroviaria Italiana Rifle Factory, Ishapore- an arms manufacturing facility located at...


Silicone tubing is sometimes used in automotive intake systems (especially for engines with forced-induction) . Forced induction is a term used to describe internal combustion engines that are not naturally aspirated. ...


Sheet silicone is used to manufacture gaskets used in automotive engines, transmissions and other applications. Some seals and gaskets 1. ... “Gearbox” redirects here. ...


Automotive body manufacturing plants and paint shops must avoid the presence of all silicones, as they may cause "fish eyes," small, circular craters that appear in the finish.


Cookware

Silicone is becoming an important product in the cookware industry, particularly bakeware and kitchen utensils. It is also used as an insulator in heat resistant potholders and similar, however it is more conductive of heat than the less dense fiber-based ones. Silicone oven mitts are able to withstand temperatures up to 500°F (260°C), and allow reaching into boiling water.[5]


Dry cleaning

Liquid silicone can be used as a dry cleaning solvent. Touted as an "environmentally friendly" alternative to the traditional perchloroethylene (or perc) solvent, the decamethylpentacyclosiloxane (D5) process has been patented by the company GreenEarth Cleaning. Dry cleaning is any cleaning process for clothing and textiles using an organic solvent other than water — generally known as dry cleaning fluid, and typically this is tetrachloroethylene. ... For other uses, see Solvent (disambiguation). ... Tetrachloroethylene Cl2C=CCl2 is a manufactured chemical that is widely used for the dry cleaning of fabrics and for metal-degreasing. ... Siloxanes are a class of both organic and inorganic chemical compounds which consist entirely of silicon, oxygen, and an alkyl group. ... GreenEarth® Cleaning is a patented process for drycleaning using liquid silicone (decamethylpentacyclosiloxane, or D5), a clear, odorless, non-toxic solvent solution. ...


The solvent degrades into silica and trace amounts of water and CO2, and waste produced from the D5 drycleaning process is nontoxic and nonhazardous. This significantly reduces the environmental impact of a typically high-polluting industry. The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Carbon dioxide is an atmospheric gas composed of one carbon and two oxygen atoms. ...


Additionally, liquid silicone is chemically inert, meaning it does not react with fabrics or dyes during the cleaning process. This reduces the amount of fading and shrinking that most dry-cleaned garments experience.


Electronic

Electronic components are sometimes protected by enclosing them in silicone to increase stability against mechanical and electrical shock, radiation and vibration. This is often called "potting". There are very few or no other articles that link to this one. ...


Silicones are used when durability and high performance are demanded of components under hard conditions, as in space (satellite technology). They are selected over polyurethane or epoxy encapsulation when a wide operating temperature range is required (−65 to 315 °C). Silicones also have the advantage of little exothermic heat rise during cure, low toxicity, good electrical properties and high purity. A polyurethane, commonly abbreviated PU, is any polymer consisting of a chain of organic units joined by urethane links. ... In chemistry, epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in...


The use of silicones in electronics is not without problems, however. Silicones are relatively expensive and can be attacked by solvents.[1] Silicone easily migrates as either a liquid or vapor onto other components.


Silicone contamination of electrical switch contacts can lead to failures by causing an increase in contact resistance, often late in the life of the contact, well after any testing is completed.[2] Use of silicone-based spray products in electronic devices during maintenance or repairs can cause later failures.


Firestops

Silicone foams have been used in North American buildings in an attempt to firestop openings within fire-resistance-rated wall and floor assemblies to prevent the spread of flames and smoke from one room to another. Firestop after fire exposure during fire test in Tulsa, Oklahoma. ...


Israeli installations switched to an "elastomer" version, which avoids most safety concerns associated with the foams. The term elastomer is often used interchangeably with the term rubber, and is preferred when referring to vulcanisates. ...


Silicone foam firestops have been the subject of controversy and press attention due to smoke development from pyrolysis of combustible components within the foam, hydrogen gas escape, shrinkage and cracking. These problems have been exposed by whistleblower Gerald W. Brown and have led to a large number or reportable events among licensees (operators of nuclear power plants) of the Nuclear Regulatory Commission (NRC). This article is about the chemistry of hydrogen. ... Poster in support of whistleblower legislation A whistleblower is an employee, former employee, or member of an organization, especially a business or government agency, who reports misconduct to people or entities that have the power and presumed willingness to take corrective action. ... Whistleblower Gerald W. Brown. ... A nuclear power station. ... NRC headquarters in Rockville, MD. Nuclear Regulatory Commission (or NRC) is a United States government agency that was established by the Energy Reorganization Act in 1974, and was first opened January 19, 1975. ...


When properly installed, silicone-foam firestops can be fabricated for building code compliance. Advantages include flexibility and high dielectric strength. Disadvantages include combustibility (hard to extinguish) and significant smoke development. A dielectric is a nonconducting substance, i. ...


Lubricants

Silicone greases are used for many purposes, such as bicycle chains. A dry-set lubricant is delivered with a solvent carrier to penetrate the chain. The solvent evaporates, leaving a clear film that lubricates but does not attract dirt and grit as much as a a traditional "wet" lubricant. Grease is a lubricant of higher initial viscosity than oil, consisting originally of a calcium, sodium or lithium soap jelly emulsified with mineral oil. ...


Medicine

Silicone, particularly the gel form, is used in bandages and dressings, in breast implants and a variety of other medical uses. Bandages are also used in martial arts to prevent dislocated joints. ... A breast implant is a prosthesis used to enlarge the size of a womans breasts (known as breast augmentation, breast enlargement, mammoplasty enlargement, augmentation mammoplasty or the common slang term boob job) for cosmetic reasons; to reconstruct the breast (e. ...


Moldmaking

Two-part silicone systems are used to create rubber molds which can be used for production casting of resins, foams, rubber and low-temp alloys.


A mold made of silicone generally requires little or no mold release or surface preparation as most materials do not adhere to moldmaking silicone.


Personal care

Silicones are ingredients in some leave-in hair conditioner products. These lessen frizz by using silicone's water resistance to prevent humidity from entering a dry hair shaft. Hair conditioner is a hair care product that improves the texture and appearance of human hair. ...


Silicones are also used in some personal lubricants. Menstrual cups are often made of silicone for its durability and reusability. Silicone is also material of choice for soft sex toys, due to its durability, cleanability and lack of pthalates, chemicals suspected of having carcinogenic and mutagenic effects on the skin and mucus membranes.[3][4][5] One review of the health risks of phthalates advocated moving away from medical devices containing phthalates because of their toxicity.[6] Wikipedia does not yet have an article with this exact name. ... This article or section does not cite any references or sources. ... A sex toy is a term for any object or device that is primarily used in facilitating human sexual pleasure. ... R,R=CnH2n+1; n=4-15 Phthalates are a group of chemical compounds that are mainly used as plasticizers -- substances added to plastics to increase their flexibility. ...


Plumbing and building construction

The strength and reliability of silicone rubber is widely acknowledged in the construction industry. Silicone rubber is a polymer that has a backbone of silicon oxygen linkages, the same bond that is found in quartz, glass and sand. ...


One-part silicone sealants and caulks are in common use to seal gaps, joints and crevices in buildings. One-part silicones cure by absorbing atmospheric moisture, which helps in the professional installation. Self-leveling silicone firestop system used around pipe through-penetration in a two-hour fire-resistance rated concrete floor assembly. ... For a description of caulking in computer game creation, refer to caulking (computer games) Caulking is a process used in the sealing of the seams in wooden boats and making them watertight. ...


In plumbing, silicone grease is typically applied to O-rings in faucets and valves. Whist the film is extant it prevents lime from sticking to the brasswork.


Toys

Silicone balls have become a juggler's favorite due to the high bounce back, and are used as a response system in many low response yo-yos.[citation needed] Juggling is a form of skillful, often artful, object manipulation. ...


Versatile applications

Silicone Industry Trade Organizations

The leading global manufacturers of silicone base materials belong to three regional organizations: the European Silicone Center(CES) in Brussels, Belgium; the Silicone Environment Health and Safety Council(SEHSC) in Washington, USA; and the Silicone Industry Association of Japan (SIAJ) in Tokyo, Japan. A fourth organization, the Global Silicone Council (GSC) acts as an umbrella structure over the regional organizations. All four are nonprofit making and have no commercial role. Their primary mission is to promote the safety of silicones from a health, safety and environmental perspective. As the European chemical industry is getting prepared to implement the REACH legislation, CES is leading the formation of a consortium[7] of silicones, silanes and siloxanes producers and importers to facilitate data and cost sharing. Registration, Evaluation and Authorisation of Chemicals (REACH) is a piece of legislation in the European Union covering the production and use of chemical substances. ...


See also

Whistleblower Gerald W. Brown. ... A breast implant is a prosthesis used to enlarge the size of a womans breasts (known as breast augmentation, breast enlargement, mammoplasty enlargement, augmentation mammoplasty or the common slang term boob job) for cosmetic reasons; to reconstruct the breast (e. ... A breast prosthesis is a silicone breast form intended to replace a lost breast. ... Firestop after fire exposure during fire test in Tulsa, Oklahoma. ... Self-leveling silicone firestop system used around pipe through-penetration in a two-hour fire-resistance rated concrete floor assembly. ... Tin Liquid Silicone Rubber (LSR) is injection molded to produce pliable, durable parts in high volume. ... Institute 2, Israel Atomic Energy Commission (IAEC), Dimona, photographed by Mordechai Vanunu The Negev Nuclear Research Center is an Israeli nuclear installation located in the Negev desert, near the city of Dimona, at . ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Core of a small nuclear reactor used for research. ... NRC headquarters in Rockville, MD. Nuclear Regulatory Commission (or NRC) is a United States government agency that was established by the Energy Reorganization Act in 1974, and was first opened January 19, 1975. ... German parchmenter, 1568 Parchment is a material for the pages of a book or codex, made from fine calf skin, sheep skin or goat skin. ... Dry cleaning is any cleaning process for clothing and textiles using an organic solvent other than water — generally known as dry cleaning fluid, and typically this is tetrachloroethylene. ... Dental dams or rubber dams are essentially rectangular sheets of latex used in dentistry, specifically endodontic therapy. ...

References

  1. ^ See Resin casting for how silicones can be dispensed in circuit board production.
  2. ^ See chapter 16.4.1 of Electrical Contacts: Principles and Applications By Paul G. Slade (image available online via GoogleBooks). Also, "A Comparison for the Effects of Various Forms of Silicon Contamination on Contact Performance" by Witter, G. (Published in "Components, Hybrids, and Manufacturing Technology, IEEE Transactions on" Mar 1979).
  3. ^ [1] W.M. Kluwe, "Carcinogenic potential of phthalic acid esters and related compounds: structure-activity relationships", Environmental Health Perspectives, Vol. 65: pp. 271–278 (March 1986).
  4. ^ [2] Norbert H. Kleinsasser, Ernst R. Kastenbauer, Herbert Weissacher, Ruth K. Muenzenrieder, Ulrich A. Harréus, "Phthalates demonstrate genotoxicity on human mucosa of the upper aerodigestive tract", Environmental and Molecular Mutagenesis Vol. 35, No. 1, pp. 9-12 (2000)
  5. ^ [3] Walter J. Kozumbo, Rosanna Kroll, Robert J. Rubin, "Assessment of the Mutagenicity of Phthalate Esters", Environmental Health Perspectives, Vol. 45, pp. 103-109 (Nov. 1982)
  6. ^ [4] Joel A. Tickner, Ted Schettler, Tee Guidotti, Michael McCally, Mark Rossi "Health risks posed by use of Di-2-ethylhexyl phthalate (DEHP) in PVC medical devices: A critical review", American Journal of Industrial Medicine Vol. 39, No. 1, pp. 100-111 (2001)
  7. ^ REACH consortium

There are very few or no other articles that link to this one. ...

External links

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Look up Silicone in
Wiktionary, the free dictionary.
Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ... Edward John Ed Markey (born July 11, 1946) has been a Democratic member of the United States House of Representatives since 1976, representing the 7th District of Massachusetts. ...

  Results from FactBites:
 
Chemistry : Periodic Table : silicon : key information (365 words)
Silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites.
Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen.
Silicon is found also in minerals such as asbestos, feldspar, clay and mica.
Silicon - LoveToKnow 1911 (2378 words)
Silicon hydride, SiH4, is obtained in an impure condition, as a spontaneously inflammable gas, by decomposing magnesium silicide with hydrochloric acid, or by the direct union of silicon and hydrogen in the electric arc.
Silicon nitrogen hydride, SiNH, is a white powder formed with silicon amide when ammonia gas (diluted with hydrogen) is brought into contact with the vapour of silicon chloroform at -10° C. Trianilino silicon hydride, SiH (NHC 6 H 5) 3, is obtained by the action of aniline on a benzene solution of silicon chloroform.
From the alloy containing 25% of silicon, the excess of magnesium is removed by a mixture of ethyl iodide and ether and a residue consisting of slate-blue octahedral crystals of magnesium silicide is left.
  More results at FactBites »

 
 

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