SILOXANE

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 (O2-) atom. 

CAS Number : 63148-62-9
EC  Number : 205-492-2
Molecular Formula :    C8H24O2Si3
Molecular Weight  :     236.53

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.

Structure of Siloxane
Siloxane generally adopt structures expected for linked tetrahedral ("sp3-like") centers. 
The Si−O bond length is 1.64 Å (vs Si–C distance of 1.92 Å) and the Si-O-Si angle is rather open at 142.5°.
By contrast, the C−O distance in a typical dialkyl ether is much shorter at 1.414(2) Å with a more acute C−O−C angle of 111°.
Siloxane can be appreciated that the siloxanes would have low barriers for rotation about the Si−O bonds as a consequence of low steric hindrance. 
This geometric consideration is the basis of the useful properties of some siloxane-containing materials, such as their low glass transition temperatures.

Synthesis of siloxanes 

The main route to siloxane functional group is by hydrolysis of silicon chlorides:

2 R3Si−Cl + H2O → R3Si−O−SiR3 + 2 HCl
The reaction proceeds via the initial formation of silanols (R3Si−OH):

R3Si−Cl + H2O → R3Si−OH + HCl
The siloxane bond can then form via a silanol + silanol pathway or a silanol + chlorosilane pathway:

2 R3Si−OH → R3Si−O−SiR3 + H2O
R3Si−OH + R3Si−Cl → R3Si−O−SiR3 + HCl
Hydrolysis of a silyldichloride can afford linear or cyclic products. 
Linear products are terminated with silanol groups:

n R2Si(OH)2 → H(R2SiO)nOH + (n − 1) H2O
Cyclic products have no silanol termini:

n R2Si(OH)2 → (R2SiO)n + n H2O
The linear products, polydimethylsiloxane (PDMS), are of great commercial value. 
Their production requires the production of dimethylsilicon dichloride.

Starting from trisilanols, cages are possible, such as the species with the formula (RSi)nO3n/2 with cubic (n = 8) and hexagonal prismatic (n = 12) structures. 
The cubic cages are cubane-type clusters, with silicon centers at the corners of a cube oxygen centres spanning each of the twelve edges.

Reactions of Siloxane
Oxidation of organosilicon compounds, including siloxanes, gives silicon dioxide. 
This conversion is illustrated by the combustion of hexamethylcyclotrisiloxane:

((CH3)2SiO)3 + 12 O2 → 3 SiO2 + 6 CO2 + 9 H2O
Strong base degrades siloxane group, often affording siloxide salts:

((CH3)3Si)2O + 2 NaOH → 2 (CH3)3SiONa + H2O
This reaction proceeds by production of silanols. 
Similar reactions are used industrially to convert cyclic siloxanes to linear polymers.

Uses of Siloxane
Siloxane, upon combustion in an inert atmosphere, generally undergo pyrolysis to form silicon oxycarbide or silicon carbide (SiC). 
By exploiting this reaction, polysiloxanes have been used as preceramic polymers in various processes including additive manufacturing. 
Polyvinyl siloxane (vinyl polysiloxane) is used to make dental impressions and industrial impressions. 
The use of a poly-siloxane precursor in polymer derived ceramics allows the formation of ceramic bodies with complex shapes, although the significant shrinkage in pyrolysis needs to be taken into account.

Cyclomethicones of Siloxane
Siloxane are a group of methyl siloxanes, a class of liquid silicones (cyclic polydimethylsiloxane polymers) that possess the characteristics of low viscosity and high volatility as well as being skin emollients and in certain circumstances useful cleaning solvents.
Unlike dimethicones, which are linear siloxanes that do not evaporate, cyclomethicones are cyclic: both groups consist of a backbone of [(CH3)2SiO]n. 
They are used in many cosmetic products including deodorants and antiperspirants which need to coat the skin but not remain tacky afterward.
Dow is a major producer of cyclomethicones.
Siloxane, like all siloxanes, degrade by hydrolysis, producing silanols.
These silanols are produced at such low levels that they do not interfere with hydrolytic enzymes.
Even though some cyclomethicones structurally resemble crown ethers, they bind metal ions only weakly.

Use and Manufacturing of Siloxane
Used as a base for extreme temperature silicone oils/fluids and as a foam suppressant in petroleum lubricating oils; Used mainly to make polydimethylsiloxane (PDMS) polymers, oligomers, and mixtures; Also used to make basic chemicals, paints, coatings, adhesives, soaps, cleaning compounds, toiletries, plastics, semiconductors, and other electronic components, and in building construction, lubricants, diluents, solvents, and cosmetics

Household Products
Household & Commercial/Institutional Products
Information on 28 consumer products that contain Trisiloxane in the following categories is provided:
-Auto Products
-Personal Care

Siloxane is a kind of organosilicon compounds which is composed of –Si–O–Si–O– backbones with side chains R attached to the silicon atoms (R2SiO), where R is a hydrogen atom or an organic radical possibly bearing functional groups. 
Polymers of siloxanes are referred as silicones, such as polydimethylsiloxane (PDMS), which is the dominant polymer in the silicone industry. 

Siloxane are commonly known as silicones. 
They belong to the organosilicon compounds and are exclusively obtained by synthesis. 
Their chemical structure determines a range of physicochemical properties which were recognized as unique. 
Due to the susceptibility to chemical modifications, ability to create short, long or complex polymer particles, siloxanes found an application in many areas of human life.

Siloxane is silicone-based compounds that are generally used for their softening, smoothing, and moistening action. 
They make products like deodorants slide on more easily, and leave hair and skin more soft and silky.
Siloxane is  in products that contain silicon such as silicone baking utensils and pans, baby nipples, and pacifiers, medical devices and implants, water-repellent windshield coating, construction lubricants and sealants as well as deodorant creams and moisturizers

Applications of Siloxane
Siloxane can be used to produce Phenyl silicone rubber
Siloxane can be used to compound medicine intermediate, silicone intermediate and macromolecular compound.

Siloxane is a polymer material containing many siloxane functional groups throughout its structure. 
Therefore, we can call this material polysiloxane. 
Siloxane is a synthetic polymer that does not appear in nature. 
This material contains a backbone, consisting of Si-O bonds. 
Moreover, there are side chains attached to this backbone. 
We usually consider this as an inorganic polymer because it has no carbon in its backbone.

Siloxane is a functional group having the Si-O-Si linkage. 
This functional group is present in organosilicon compounds. 
The siloxane compounds can be either straight chain compounds or branched compounds. 
These linkages form the backbone of the silicone polymer, i.e. polymethylsiloxane.

Siloxane is any chemical compund composed of units of the form R2SiO, where R is a hydrogen atom or a hydro carbon group. 
They belong to the wider class of Organosilicon compounds. 
Siloxanes can have branched or unbranched back bones consisting of alternating silicon and oxygen atoms ‐Si‐O‐Si‐O‐, with side chains R attached to silicon atoms. 
Polymerised Siloxanes with organic side chains are commonly known as silicones or as polysiloxanes.

APPLICATIONS OF SILOXANES:
-cosmetics (deodrants, sunblocks, hairsprays and skincare)
-personal care products (tooth pastes)
-industrial cleaning agents 

Siloxane is any of various compounds containing alternate silicon and oxygen atoms in either a linear or cyclic arrangement usually with one or two organic groups attached to each silicon atom.
Siloxanes come from the silicones that are parts in materials such as: shampoo, soaps, surfactants, oils, pharmaceutical products, and so on., which are present in the substrate during the anaerobic digestion process to which is subjected this material.
Siloxane is compound with a Si-O-Si bond functional group in silicone chemistry. 
The parent siloxanes include oligomeric and polymeric hydrides with the formulae H(OSiH2)nOH and (OSiH2)n. 
Siloxanes also include branched compounds, in which each pair of silicon centers is separated by one oxygen atom. 
The siloxane functional groups form the backbone of the siloxane, a prime example of which is polydimethylsiloxane. 
And the functional group (RO)3Si is called siloxy.

Applications of Siloxane

Industry use: 
Siloxane is a class of liquid siloxane with low viscosity and high volatility. 
Siloxane is a skin emollient and a useful cleaning solvent in some cases. 
Siloxane has short backbones that form closed or nearly closed cycles with methyl groups, giving them many of the same properties as dimethicones, but making them become more volatile. 
So Siloxane is used in many cosmetics where the ultimate complete evaporation of the siloxane carrier fluid is desired. 
In this way, Siloxane is useful for products such as deodorants and antiperspirants that need to be applied to the skin but will not be sticky afterwards.

Organic chemistry: 
Molecular capsules provide micro spaces within the molecule, where unstable species are protected and can be stabilized. 
Cyclic oligomers of trisilanol are considered as transient intermediates in the polycondensation of trialkoxysilanes, resulting in the formation of siloxane networks or ladder polymers. 
The preparation and separation of these stable forms of intermediates are not only particularly important for understanding the condensation process, but also important for the modeling of the silica surface in homogeneous systems and further conversion to silicon-based functional materials. 
If the condensation reaction of the trialkoxysilane is performed in the nanopore cavity of the self-assembled coordination cage, which shows significant binding ability to the neutral molecule, a cyclic trimer can be prepared as a stable form.

Siloxanes, which can be viewed as hybrids of glass and organic materials, have been used to fabricate polymer waveguides and devices that exploit the large thermo-optical effect of this material. 
Siloxanes have many unique properties including good thermal stability, chemical resistance, tunable refractive index, tunable mechanical properties and excellent photo-stability. 
Biogas can be produced from uncontrolled and controlled systems. 
Uncontrolled systems include landfills and marshlands, while controlled systems include wastewater treatment plants (WWTP) and anaerobic digestion plants. 
These biogas sources have high siloxane contamination, resulting from waste from industries and households.

Substance identity

EC / List no.: 205-492-2
CAS no.: 63148-62-9

Hazard classification & labelling of Siloxane
Warning! According to the classification provided by companies to ECHA in CLP notifications this substance causes serious eye irritation.

Siloxane indicated, in 2009, as being intended to be registered by at least one company in the EEA.
Siloxane for which classification and labeling data have been submitted to ECHA in a registration under REACH or notified by manufacturers or importers under CLP. 
Such notifications are required for hazardous substances, as such or in mixtures, as well as for all substances subject to registration, regardless of their hazard.

Synonyms :
polydimethylsiloxane (Mw > 6800 Da)
Polydimethylsiloxanes
Siloxanes and Silicones, di-Me
Baysilon
Dimethicone
DiMethyl Polysiloxane
dimethyl polysiloxane
DIMETHYL POLYSILOXANE (ME TERM)
Dimethyl Silicone
Dimethyl silicone
dimethyl silicone
dimethyl silicone oil
DIMETHYL SILICONES AND SILOXANES
Dimethyl siloxane
dimethyl siloxane
Dimethyl siloxanes and silicones
dimethyl(oxo)silane
dimethyl-bis(trimethylsilyloxy)silane
Dimethylepolysiloxane
Dimethylpolysiloxane
Dimethylsilicone
dimethylsiloxane
Dimethylsiloxane trimethylsiloxane terminated
Dimethylsiloxane, trymethylsilyloxy terminated
Monomers of Siloxanes and Silicones, di-Methyl 
Polidimetylosiloksan
Poly dimethyl siloxanes
poly(dimethylsilooxane)
POLY(DIMETHYLSILOXANE)
Poly(dimethylsiloxane)

poly(dimethylsiloxane)
Polydimethyisiloxane
polydimethyl siloxane
Polydimethylsiloxan
polydimethylsiloxan
POLYDIMETHYLSILOXANE
Polydimethylsiloxane
Polydimethylsiloxane,linear
Polydimethylsiloxanes
Polydimetylsiloxan
Polysiloxanes, di-Me
Silicon oil
Silicone antifoam 1430
Silicone Oil
Siloxane
Siloxane, dimethyl
Siloxanes
siloxanes and other silicones (polydimethylsiloxane)
SILOXANES AND SILICONES, DI-ME
Siloxanes and Silicones, di-Me
Siloxanes and Silicones, di-Me (CTS) (MAN)
Siloxanes and Silicones, di-Me(Polydimethylsiloxanes(PDMS))
Siloxanes and silicones, dimethyl
α,ω-trimethylsilyl terminated polydimethylsiloxane
Dimethylpolysiloxane
MED-360
Dimethicone
Dimethylpolysiloxane
Dimethylpolysiloxane Hydrolyzate (Silicone Oil)
KF96
Poly[oxy(dimethylsilylene)], α-[trimethylsilyl]-ω-[(trimethylsilyl)oxy]
Polydimethyisiloxane
Polydimethylsiloxan
Polydimethylsiloxane
Polydimethylsiloxane "Silicone Silbione fluids
Polydimethysiloxane Polymer
Polydimetylsiloxan
Silicone oil
12648-49-6
12684-12-7
1471301-69-5
1669409-87-3
1669410-33-6
167748-54-1
2028348-45-8
2161362-23-6
37221-45-7
39476-41-0
53125-20-5
63148-62-9
OCTAMETHYLTRISILOXANE
107-51-7
Trisiloxane, octamethyl-
Poly(dimethylsiloxane)
1,1,1,3,3,5,5,5-Octamethyltrisiloxane
Dimeticone
dimethyl-bis(trimethylsilyloxy)silane
Dimethicone 350
63148-62-9
Pentamethyl(trimethylsilyloxy)disiloxane
Dimethylbis(trimethylsiloxy)silane
9G1ZW13R0G
CHEBI:9147
Trisiloxane, 1,1,1,3,3,5,5,5-octamethyl-
Dimethylbis(trimethylsilyloxy)silane
Dimethicones
Poly(dimethylsiloxane), hydroxy terminated
MFCD00084411
MFCD00134211
MFCD00148360
CCRIS 3198
Poly(dimethylsiloxane), trimethylsiloxy terminated
EINECS 203-497-4
dimeticonum
UNII-9G1ZW13R0G
Dimeticona
FRD 20
Ctamethyltrisiloxane
MFCD00008264
Pentamethyl(trimethylsiloxy)disiloxane
octamethyl-trisiloxane
PDMS
dimethicone macromolecule
VOLASIL DM-1
Silicon Oil for Oil Bath
TRISILOXANE [INCI]
DM-FLUID 1.0CS
EC 203-497-4
Octamethyltrisiloxane, 98%
DSSTox_CID_20710
DSSTox_RID_79558
DSSTox_GSID_40710
OS 20 (SILOXANE)
SCHEMBL23459
Siliconoil Pharma 100 cSt.
Dimethyl polysiloxane, bis(trimethylsilyl)-terminated
Dow Corning High-Vacuum Grease
CHEMBL2142985
DTXSID9040710
CHEBI:31498
CXQXSVUQTKDNFP-UHFFFAOYSA-
KF 96A1
OCTAMETHYLTRISILOXANE [MI]
dimethylbis(trimethylsiloxy)siliane
Polydimethylsiloxane, 1000 cSt.
alpha-(Trimethylsilyl)-omega-methylpoly(oxy(dimethylsilylene))
[(CH3)3SiO]2Si(CH3)2
Tox21_301002
CO9816
MFCD00165850
Silane, dimethylbis(trimethylsiloxy)-
AKOS015840180
ZINC169747808
Antifoam compound for anhydrous systems
FS-4459
NCGC00164100-01
NCGC00164100-02
NCGC00254904-01
CAS-107-51-7
DB-040764
FT-0631598
FT-0696355
O0257
O9816
C07261
D91850
S12475
A801717
XIAMETER(R) PMX-200 SILICONE FLUID 1 CST
J-001906
Poly(dimethylsiloxane), viscosity 1.0 cSt (25 C)
Q2013799
XIAMETER(R) PMX-200 Silicone Fluid 20 CS
2,2,4,4,6,6-hexamethyl-3,5-dioxa-2,4,6-trisilaheptane
Polydimethylsiloxane, 20,000 cSt. trimethoxysilyl terminated
Polydimethylsiloxane, extreme low volatility, viscosity 1000 cSt.
Intermediate viscosity polydimethylsiloxane antifoam emulsion, 20% active, viscosity 1500cst
Intermediate viscosity polydimethylsiloxane antifoam emulsion, 30% active, viscosity 1500cst
Polydimethylsiloxane, trimethylsiloxy terminated, reduced volatility, viscosity 20 cSt.
28349-86-2
Intermediate viscosity polydimethylsiloxane antifoam emulsion, 10% active, viscosity 1000-2000cst
Intermediate viscosity polydimethylsiloxane antifoam emulsion, 10% active, viscosity 800-2000cst
Intermediate viscosity polydimethylsiloxane antifoam emulsion, 20% active, viscosity 1000-2000cst
Intermediate viscosity polydimethylsiloxane antifoam emulsion, 30% active, viscosity 1000-2000cst
Polydimethylsiloxane, trimethylsiloxy terminated, extreme low volatility, viscosity 12.500 cSt.
1112-39-6 [RN]
214-189-4 [EINECS]
Dimethoxy(dimethyl)silan [German] [ACD/IUPAC Name]
Dimethoxy(dimethyl)silane [ACD/IUPAC Name]
Diméthoxy(diméthyl)silane [French] [ACD/IUPAC Name]
Dimethoxydimethylsilane
Dimethyldimethoxysilane
DMDMS
MFCD00025691 [MDL number]
Silane, dimethoxydimethyl- [ACD/Index Name]
VV3641666
1,1-dimethoxy-1-methyl-1-silaethane
103735-12-2 [RN]
63148-62-9 [RN]
Dimethyl dimethoxysilane
Dimethyldimethoxysilane|Dimethoxydimethylsilane
DIMETHYLPOLYSILOXANE [Wiki]
Dow Corning Z-6194 [Trade name]
FS-3860
Polydimethylsiloxane [Wiki]
A3QDB1RS1C [DBID]
104906_ALDRICH [DBID]
40160_FLUKA [DBID]
556688_ALDRICH [DBID]
AY 43-004 [DBID]
CD5605 [DBID]
KBM 22 [DBID]
NSC 93882 [DBID]
NSC93882 [DBID]
TSL 8112 [DBID]
TSL 8117 [DBID]
UNII:A3QDB1RS1C [DBID]