Silicone resin

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Silicone resin with R = CH3, H or OH Silicone resin.svg
Silicone resin with R = CH3, H or OH

Silicone resins are a type of silicone material which is formed by branched, cage-like oligosiloxanes with the general formula of RnSiXmOy, where R is a non-reactive substituent, usually methyl (Me = −CH3) or phenyl (Ph = −C6H5), and X is a functional group: hydrogen (−H), hydroxyl (−OH), chlorine (−Cl) or alkoxy (−O). These groups are further condensed in many applications, to give highly crosslinked, insoluble polysiloxane networks. [1]

Contents

When R is methyl, the four possible functional siloxane monomeric units are described as follows: [2]

Note that a network of only Q groups becomes fused quartz.

The most abundant silicone resins are built of D and T units (DT resins) or from M and Q units (MQ resins), however many other combinations (MDT, MTQ, QDT) are also used in industry.

Silicone resins represent a broad range of products. Materials of molecular weight in the range of 1000–10,000 are very useful in pressure-sensitive adhesives, silicone rubbers, coatings and additives. [3] [4] Polysiloxane polymers with reactive side group functionality such as vinyl, acrylate, epoxy, mercaptan or amine, are used to create thermoset polymer matrix composites, coatings and adhesives. [5]

Silicone resins are prepared by hydrolytic condensation of various silicone precursors. In early processes of preparation of silicone resins sodium silicate and various chlorosilanes were used as starting materials. Although the starting materials were the least expensive ones (something typical for industry), structural control of the product was very difficult. More recently, a less reactive tetraethoxysilane - (TEOS) or ethyl polysilicate and various disiloxanes are used as starting materials. [1]

Microbial deterioration

The algae Stichococcus bacillaris, and certain fungal species have been seen to colonize silicone resins used at archaeological sites. [6]

See also

Related Research Articles

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A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking utensils, thermal insulation, and electrical insulation. Some common forms include silicone oil, silicone grease, silicone rubber, silicone resin, and silicone caulk.

<span class="mw-page-title-main">Epoxy</span> Type of material

Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also collectively called epoxy. The IUPAC name for an epoxide group is an oxirane.

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<span class="mw-page-title-main">Polydimethylsiloxane</span> Chemical compound

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<span class="mw-page-title-main">Siloxane</span> Si–O–Si chemical bond

A siloxane is a functional group in organosilicon chemistry with the Si−O−Si linkage. The parent siloxanes include the oligomeric and polymeric hydrides with the formulae H(OSiH2)nOH and (OSiH2)n. Siloxanes also include branched compounds, the defining feature of which is that each pair of silicon centres is separated by one oxygen (O) atom. The siloxane functional group forms the backbone of silicones, the premier example of which is polydimethylsiloxane (PDMS). The functional group R3SiO− (where the three Rs may be different) is called siloxy. Siloxanes are manmade and have many commercial and industrial applications because of the compounds’ hydrophobicity, low thermal conductivity, and high flexibility.

In inorganic chemistry, chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The parent chlorosilane is silicon tetrachloride.

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Hot-melt adhesive (HMA), also known as hot glue, is a form of thermoplastic adhesive that is commonly sold as solid cylindrical sticks of various diameters designed to be applied using a hot glue gun. The gun uses a continuous-duty heating element to melt the plastic glue, which the user pushes through the gun either with a mechanical trigger mechanism on the gun, or with direct finger pressure. The glue squeezed out of the heated nozzle is initially hot enough to burn and even blister skin. The glue is sticky when hot, and solidifies in a few seconds to one minute. Hot-melt adhesives can also be applied by dipping or spraying, and are popular with hobbyists and crafters both for affixing and as an inexpensive alternative to resin casting.

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Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si(CH3)2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made on an industrial scale as the principal precursor to dimethylsilicone and polysilane compounds.

<span class="mw-page-title-main">Methyltrichlorosilane</span> Chemical compound

Methyltrichlorosilane, also known as trichloromethylsilane, is a monomer and organosilicon compound with the formula CH3SiCl3. It is a colorless liquid with a sharp odor similar to that of hydrochloric acid. As methyltrichlorosilane is a reactive compound, it is mainly used a precursor for forming various cross-linked siloxane polymers.

<span class="mw-page-title-main">Silsesquioxane</span> Molecular compound with applications in ceramics

A silsesquioxane is an organosilicon compound with the chemical formula [RSiO3/2]n. Silsesquioxanes are colorless solids that adopt cage-like or polymeric structures with Si-O-Si linkages and tetrahedral Si vertices. Silsesquioxanes are members of polyoctahedral silsesquioxanes ("POSS"), which have attracted attention as preceramic polymer precursors to ceramic materials and nanocomposites. Diverse substituents (R) can be attached to the Si centers. The molecules are unusual because they feature an inorganic silicate core and an organic exterior. The silica core confers rigidity and thermal stability.

A thermoset polymer matrix is a synthetic polymer reinforcement where polymers act as binder or matrix to secure in place incorporated particulates, fibres or other reinforcements. They were first developed for structural applications, such as glass-reinforced plastic radar domes on aircraft and graphite-epoxy payload bay doors on the Space Shuttle.

Polysilazanes are polymers in which silicon and nitrogen atoms alternate to form the basic backbone. Since each silicon atom is bound to two separate nitrogen atoms and each nitrogen atom to two silicon atoms, both chains and rings of the formula occur. can be hydrogen atoms or organic substituents. If all substituents R are H atoms, the polymer is designated as Perhydropolysilazane, Polyperhydridosilazane, or Inorganic Polysilazane ([H2Si–NH]n). If hydrocarbon substituents are bound to the silicon atoms, the polymers are designated as Organopolysilazanes. Molecularly, polysilazanes are isoelectronic with and close relatives to Polysiloxanes (silicones).

Organosilicon water repellent:

<span class="mw-page-title-main">Polymer derived ceramics</span>

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1,4-Cyclohexanedimethanol diglycidyl ether is an organic chemical in the glycidyl ether family. It has the formula C14H24O4 and the IUPAC name is 2-[[4-(oxiran-2-ylmethoxymethyl)cyclohexyl]methoxymethyl]oxirane, and the CAS number 14228-73-0. It is REACH registered in Europe. It is an industrial chemical and a key use is in the reduction of viscosity of epoxy resin systems functioning as a reactive diluent.

<span class="mw-page-title-main">Trimethylolpropane triglycidyl ether</span> Chemical compound

Trimethylolpropane triglycidyl ether (TMPTGE) is an organic chemical in the glycidyl ether family. It has the formula C15H26O6 and the IUPAC name is 2-[2,2-bis(oxiran-2-ylmethoxymethyl)butoxymethyl]oxirane, and the CAS number 3454-29-3. It also has another CAS number of 30499-70-8 A key use is as a modifier for epoxy resins as a reactive diluent.

<span class="mw-page-title-main">Trimethylolethane triglycidyl ether</span> Chemical compound

Trimethylolethane triglycidyl ether (TMETGE) is an organic chemical in the glycidyl ether family. It has the formula C14H24O6 and the IUPAC name is 2-({2-methyl-3-[(oxiran-2-yl)methoxy]-2-{[(oxiran-2-yl)methoxy]methyl}propoxy}methyl)oxirane. The CAS number is 68460-21-9. A key use is as a modifier for epoxy resins as a reactive diluent.

References

  1. 1 2 S.J. Clarson, J.A. Semlyen, Siloxane Polymers, Prentice Hall, New Jersey (1993).
  2. Dow Corning nomenclature of silicon resins
  3. List of silicone resins produced by Dow Corning
  4. Database of silicon resins produced by Momentive Performance Materials (formerly GE Silicones)
  5. B. Boutevin et al., in Silicon-Containing Polymers, ed. RG Jones et al., Springer, Netherlands, 2000, pp 79-112, ISBN   978-1-4020-0348-6
  6. Francesca Cappitelli; Claudia Sorlini (2008). "Microorganisms Attack Synthetic Polymers in Items Representing Our Cultural Heritage". Applied and Environmental Microbiology. 74 (3): 564–9. Bibcode:2008ApEnM..74..564C. doi:10.1128/AEM.01768-07. PMC   2227722 . PMID   18065627.