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Silicone is often confused with one of its constituent elements, silicon, but they are distinct substances. Silicon is a chemical element, a hard dark-grey semiconducting metalloid, which in its crystalline form is used to make integrated circuits ("electronic chips") and solar cells. Silicones are compounds that contain silicon, carbon ...
To make silicone, the silicon atoms must be isolated from the silicon dioxide compound silica. This is done by heating large volumes of quartz sand to extremely high temperatures, often up to 1800 °C. From here, there are several processes where silicon is combined with methyl chloride and heated.
Oxidation of organosilicon compounds, including siloxanes, gives silicon dioxide. This conversion is illustrated by the combustion of hexamethylcyclotrisiloxane: ((CH 3) 2 SiO) 3 + 12 O 2 → 3 SiO 2 + 6 CO 2 + 9 H 2 O. Strong base degrades siloxane group, often affording siloxide salts: ((CH 3) 3 Si) 2 O + 2 NaOH → 2 (CH 3) 3 SiONa + H 2 O
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO 2, commonly found in nature as quartz. [5] [6] In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product.
The silicon to hydrogen bond is longer than the C–H bond (148 compared to 105 pm) and weaker (299 compared to 338 kJ/mol). Hydrogen is more electronegative than silicon hence the naming convention of silyl hydrides. Commonly the presence of the hydride is not mentioned in the name of the compound. Triethylsilane has the formula Et 3 SiH.
Silicone resin with R = CH 3, H or OH. Silicone resins are a type of silicone material which is formed by branched, cage-like oligosiloxanes with the general formula of R n SiX m O y, where R is a non-reactive substituent, usually methyl (Me = −CH 3) or phenyl (Ph = −C 6 H 5), and X is a functional group: hydrogen (−H), hydroxyl (−OH), chlorine (−Cl) or alkoxy (−O −).
The rubbery, vinegary-smelling silicone caulks, adhesives, and aquarium sealants are also well-known. PDMS is also used as a component in silicone grease and other silicone based lubricants, as well as in defoaming agents, mold release agents, damping fluids, heat transfer fluids, polishes, cosmetics, hair conditioners and other applications.
Silicon and silicon carbide readily react with all four stable halogens, forming the colourless, reactive, and volatile silicon tetrahalides. [11] Silicon tetrafluoride also may be made by fluorinating the other silicon halides, and is produced by the attack of hydrofluoric acid on glass. [12]