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Cyclomethicone 4 is an odorless, colorless non-oily silicone fluid which has C8H24O4Si4 as chemical formula.
Cyclomethicone 4 is a cyclic organic silicon substance which can be used as monomer in the production of silicone polymers such as rubber, resins and greases.
Cyclomethicone 4 is a cyclosiloxane that is the octamethyl derivative of cyclotetrasiloxane.
CAS Number: 556-67-2
Molecular Formula: C8H24O4Si4
Molecular Weight: 296.62
EINECS Number: 209-136-7
Synonyms:Octamethylcyclotetrasiloxane, 556-67-2, Cyclotetrasiloxane octamethyl-, 2,2,4,4,6,6,8,8-Octamethyl-1,3,5,7-tetroxatetrasilocane, OMCTS, Cyclic dimethylsiloxane tetramer, Cyclomethicone-4, Silicone SF 1173, NUC silicone VS 7207, Union Carbide 7207, D4 Cyclomethicone, Dimethylsiloxane cyclic tetramer, Polysiloxane D4 CRS, Octamethyl-cyclotetrasiloxane, Oktamethylcyklotetrasiloxan, Oktamethylzyklotetrasiloxan, 209-136-7, EINECS 209-136-7, C8H24O4Si4, EC 209-136-7, RefChem:167770, CHEBI:25640, MFCD00003269, CCRIS 1327, HSDB 6131, UNII-CZ227117JE, NSC-345674, DTXSID7027205, DTXCID107205, SCHEMBL18354, BIDD:ER0157, orb2945038, CHEMBL1869229, Q2013804, O0142, O9810, F83065, CS-0213747, NS00043628, KF 994, VS 7207, SF 1173, UC 7207, MSK002144, AKOS008901191, Tox21_201398, Tox21_300547, NCGC00164099-01, NCGC00164099-02, NCGC00164099-03, NCGC00254406-01, NCGC00258949-01, BRN 1787074, CYCLOMETHICONE-4 [USP-RS], OCTAMETHYLCYCLOTETRASILOXANE [HSDB], Analytical Standard Octamethylcyclotetrasiloxane, Cyclotetrasiloxane 2,2,4,4,6,6,8,8-octamethyl-, CAS-556-67-2, CAS 25037-57-4 (polymeric listing), JACS-556-67-2;uc7207;unioncarbide7207;vs7207;Octamethylcyclotetrasiloxane,98%;1H-Benzimidazol-2-yl-carbamic Acid Methyl Ester-d4;2-Benzimidazolecarbamic Acid Methyl Ester-d4;BAS-3460-d4
Cyclomethicone 4 is also known as D4.
Cyclomethicone 4 is an organosilicon compound and a cyclosiloxane.
Cyclomethicone 4 derives from a hydride of a cyclotetrasiloxane.
Commercially Cyclomethicone 4 is produced from dimethyldichlorosilane.
Cyclomethicone 4 is added dropwise to water, the temperature is maintained at 30-40°C, stratified, the acid water is released, the oily material is hydrolyzed with sodium hydroxide solution, the hydrolysate and 0.5%-2% potassium hydroxide are added to the cracking kettle and cracked at 120-140°C and 99.8 kPa vacuum.
The cracked material is fractionated and the fraction is collected at 173-176°C to obtain octamethylcyclotetraoxysilane.
Cyclomethicone 4 is a volatile methylsiloxane (VMS) with a relatively low molecular weight.
This silicone fluid has a silicon-oxygen bond in a cyclic arrangement and methyl groups are attached to the silicon atom.
Cyclomethicone 4 can be used in the manufacture of silicone based polymers for use in medical devices and personal care products.
Cyclomethicone 4 is another commercial name for Octamethylcyclotetrasiloxane (D4), a cyclic siloxane composed of four repeating Si–O units, each carrying two methyl groups.
It is a volatile, hydrophobic, low-viscosity silicone fluid known for excellent spreading, smooth sensory feel, and rapid evaporation from surfaces.
Because it leaves almost no residue after evaporation, it is frequently used as a temporary carrier for other ingredients.
Its ring-shaped siloxane structure provides strong thermal stability and oxidative resistance, making it reliable in both cosmetic and industrial applications.
The methyl substituents significantly reduce surface tension, enabling easy distribution over skin, hair, and substrates.
This balance of volatility and stability defines its performance advantages compared to straight-chain silicones.
Cyclomethicone 4 or Cyclomethicone 4 belongs to the family of liquid methyl siloxanes known as cyclomethicones.
Cyclomethicone 4 is also called Octamethylcyclotetrasiloxane and is a cyclosiloxane that is the octamethyl derivative of cyclotetrasiloxane.
Cyclomethicone 4 is a super light silicone that is the small sister of the more commonly used 5-unit long cyclic structured Cyclopentasiloxane.
Cyclomethicone 4 is used as an emollient and solvent in cosmetics.
Cyclomethicone 4 is member of cyclomethicone, which are a group of liquid methyl siloxanes that have low viscosity and high volatility.
Cyclomethicone 4 are cyclic in structure with a monomer backbone of one silicon and two oxygen atoms bonded together.
Cyclomethicone 4 is used in cosmetic and personal products as a skin emollient.
Cyclomethicone 4, also known as D5 and D5, is an organosilicon compound with the formula [(CH3)2SiO]5.
It is a colorless and odorless liquid that is slightly volatile.
Cyclomethicone 4 is used in various cosmetic products.
It also is used as a dry cleaning solvent and has been marketed as an "eco-friendly" and "green" alternative to perchloroethylene in the 2000s, under the tradename GreenEarth.
Cyclomethicone 4 is persistent in nature and bioaccumulative.
Cyclomethicone 4 is acutely non-toxic but its long-term health effects are unknown.
It’s a silicone-based product used in the cosmetics industry.
In conservation, it’s useful mainly due to its ability to temporarily waterproof a material.
Silicone-based solvents are volatile – they are thought to evaporate completely from surfaces, leaving no residues.
They repel water, but their polarity is so dramatically low that they fall completely outside the Teas solubility triangle and cannot dissolve fats or oils.
In fact, they are sometimes referred to as non-solvents.
Cyclomethicone 4 solvents are already used for safely cleaning acrylic paint films and for cleaning natural history specimens, such as feathers and bones, where the silicone serves to protect surfaces from absorbing chemicals during cleaning.
The same properties make them ideal for use on leather, as they don’t alter its natural composition.
Melting point: 17–18 °C (lit.)
Boiling point: 175–176 °C (lit.)
Density: 0.956 g/mL at 25 °C (lit.)
Vapor density: 1 (vs air)
Vapor pressure: 1.32 hPa at 25 °C
Refractive index: n²⁰/D 1.396 (lit.)
Flash point: 140 °F
Storage temp.: Store below +30 °C
Solubility: <0.001 g/L (hydrolysis)
Form: Liquid
Color: Colorless
Specific gravity: 0.956
Explosive limit: 0.4–11.7 % (v/v)
Biological source: Rabbit
Viscosity: 1.6 mm²/s
Water solubility: Insoluble
Sensitive: Moisture sensitive
Merck: 14,6747
BRN: 1787074
Dielectric constant: 2.4 at 20 °C
InChIKey: HMMGMWAXVFQUOA-UHFFFAOYSA-N
LogP: 6.98 at 21.7 °C
Cyclomethicone 4, also called D4, is an organosilicon compound and one of a number of cyclic siloxanes (cyclomethicones).
It is a colorless viscous liquid with a high boiling point.
Cyclomethicone 4 has historically been used on a large scale in personal care products including cosmetics, hair conditioners and emollients (moisturising creams), Global production in 1993 was 136,000 tons, however it is now facing significant pressure from regulators.
Cyclomethicone 4 is a substance of very high concern In the EU, where it was classified as a PBT and effectively banned in personal care products in 2018.
The US EPA began reevaluating its risks in 2020.
Replacements include branched-chain alkanes (isoparaffins).
Commercially Cyclomethicone 4 is produced from dimethyldichlorosilane.
Hydrolysis of the dichloride produces a mixture of cyclic dimethylsiloxanes and polydimethylsiloxane.
From this mixture, the cyclic siloxanes including D4 can be removed by distillation.
In the presence of a strong base such as KOH, the polymer/ring mixture is equilibrated, allowing complete conversion to the more volatile cyclic siloxanes: [(CH3)2SiO]4n → n [(CH3)2SiO]4
Cyclomethicone 4 and D5 are also precursors to the polymer.
Cyclomethicone 4 is of low acute toxicity.
The LC50 for a single four hour inhalation exposure in rats is 36 mg/L.
The oral LD50 in rats is above 4800 mg/kg and the dermal LD50in rats is above 2400 mg/kg.
As the smallest cyclic dimethylsiloxane that does not experience considerable ring strain, Cyclomethicone 4 is one of the most abundant siloxanes in the environment, e.g. in landfill gases.
Cyclomethicone 4 and D5 have attracted attention because they are pervasive.
Cyclic siloxanes can be detected in some species of aquatic life.
An independent, peer-reviewed study in the US found "negligible risk from Cyclomethicone 4 to organisms" while a scientific assessment by the Australian government stated, "the direct risks to aquatic life from exposure to these chemicals at expected surface water concentrations are not likely to be significant."
In the European Union, Cyclomethicone 4 was characterized as a substance of very high concern (SVHC) due to its PBT and vPvB properties and was thus included in the candidate list for authorisation.
Cyclomethicone 4 shall not be placed on the market in wash-off cosmetic products in a concentration equal to or greater than 0.1% by weight of either substance, after 31 January 2020.
Conversely, a detailed review and analysis of the science by the State of Washington in 2017 led to the removal of Cyclomethicone 4 from their CHCC listing.
That decision prompted the State of Oregon to follow suit in 2018.
Cyclomethicone 4 is widely used in personal-care formulations, including deodorants, hair conditioners, foundations, sprays, and waterproof cosmetics.
It delivers a light, silky feel and improves the application properties of active ingredients.
After spreading the product, it evaporates cleanly, enhancing comfort and reducing greasiness.
In industrial settings, it can function as a solvent, lubricant, or intermediate in silicone polymer synthesis.
Cyclomethicone 4 undergoes ring-opening polymerization to produce silicone elastomers and PDMS-based materials.
These polymers are essential in coatings, sealants, medical devices, and electronics.
Physically, Cyclomethicone 4 is a clear, water-insoluble liquid with a low odor and high vapor pressure.
Cyclomethicone 4 is designed to be non-occlusive, allowing breathability when used on skin.
However, due to its lipophilic nature, it may bioaccumulate in aquatic life, resulting in regulatory scrutiny in certain regions.
Uses:
Cyclomethicone 4 is used as a monomer in the production of silicone polymers and as an intermediate in the production of other organosilicon substances.
Further it finds its application in electronics, textiles, personal care products and household care products.
Cyclomethicone 4 by the Polymerization of Octamethylcyclotetrasiloxane: To a resin flask equipped with a thermometer, stirrer, and reflux eondenser is added 1000 gm of octamethylcyclotetrasiloxane.
The siloxane is heated to 165°C, and then 0.14gm of a potassium hydroxide-isopropanol complex (neutral equivalent = 193.5) is added to give a Si : Κ ratio of 4470:1.
In 25 min the stirrer begins to stall, and the polymer is now heated for 3(1/2) hr at 150°C to complete polymerization.
The resulting polymer has an intrinsic viscosity of 1.5 dl/gm corresponding to a molecular weight of 804,600.
Cyclomethicone 4 is widely used in cosmetic and personal-care products as a volatile silicone carrier.
Cyclomethicone 4 spreads easily on skin and hair to improve texture during application.
Then it evaporates quickly, leaving little to no residue.
Cyclomethicone 4 functions as a feel-enhancer in makeup, lotions, deodorants, and hair care.
The low-viscosity silicone provides a smooth, silky, non-greasy finish.
This improves user comfort and product sensory performance.
It is used in fragrance and active-ingredient delivery systems.
The volatility of the liquid allows controlled transfer of scents or dissolved components to the skin.
This enhances both aroma release and functional efficiency.
Cyclomethicone 4 serves as a temporary lubricant in formulations that require spreadability but not long-term greasiness.
Its mobility supports smooth application over large surface areas.
After application it dries off, preventing buildup.
Cyclomethicone 4 is employed in coating and finishing technologies for polymers, textiles, and surfaces.
Its rapid evaporation helps form even films without defects.
This supports high-quality finishing in commercial products.
Cyclomethicone 4 acts as a processing intermediate in silicone manufacturing.
Through ring-opening polymerization, it forms PDMS and other silicone materials.
These become key components in industrial sealants, elastomers, and electronic materials.
Cyclomethicone 4 can cause mild skin irritation, especially with repeated or prolonged contact.
Dryness or redness may develop if protective measures are not used.
Gloves are recommended during handling.
Eye exposure may lead to temporary irritation or tearing.
Splashes should be rinsed with clean water immediately.
Protective eyewear reduces the risk of accidental contact.
Inhalation of vapors or aerosols may irritate the respiratory system.
Symptoms can include coughing or mild throat discomfort.
Proper ventilation is advised when working with the liquid in open vessels.
Cyclomethicone 4 is a flammable liquid, and vapors may form ignitable mixtures with air.
Ignition sources such as flames and sparks must be avoided.
Proper storage in flame-resistant containers is required.
Cyclomethicone 4 can bioaccumulate in aquatic organisms due to its strong lipophilicity.
Long-term environmental exposure may pose risks to aquatic ecosystems.
Disposal should follow regulatory guidelines for silicone materials.
Repeated or high-dose exposure may affect the liver or endocrine system based on animal studies.
Although typical product use is considered low-risk, caution is recommended for occupational handling.
Hygiene measures such as washing hands after use should always be followed.
Cyclomethicone 4 may produce static discharge if handled in high-flow pumping systems.
This can create an unexpected ignition hazard in industrial environments.
Grounding and bonding measures are recommended during transfer operations.
Cyclomethicone 4 may decompose at elevated temperatures, releasing irritating vapors or small amounts of formaldehyde-like compounds.
These breakdown products can increase inhalation risks in confined spaces.
Thermal processing should include effective ventilation controls.
Accidental ingestion is considered harmful and may cause stomach irritation or nausea.
Medical evaluation is necessary if swallowed.
Food and beverages must not be stored or consumed near handling areas.
Cyclomethicone 4 can penetrate porous materials like fabric or rubber due to its high mobility.
This may increase skin contact duration if contaminated clothing is not removed promptly.
Contaminated garments should be washed before reuse.
Mist or aerosol exposure can lead to lung irritation under poorly controlled spray conditions.
Effects may include short-term breathing difficulty or discomfort.
Respiratory protection is recommended when spraying the material.
Cyclomethicone 4 may cause headache or dizziness if vapors accumulate in low-ventilation indoor spaces.
These effects indicate excessive airborne concentrations.
Monitoring air quality ensures safe occupational exposure levels.
Safety Profile:
Cyclomethicone 4 can interfere with the body’s hormones.
In animals, it can affect the reproductive system.
Cyclomethicone 4 is classified as a category 1 endocrine disruptor by the European Commission.
A 2018 study commissioned by the Danish EPA identified D4 as an endocrine disruptor.
The Global Harmonized System Label Requirements classified D4 as suspected to produce reproductive toxicity.
Cyclomethicone 4 was added to the Toxic Substances Control Act work plan due to reproductive toxicity, moderate environmental persistence, and high bioaccumulation potential.
Adverse reproductive effects including estrogenic effects have been observed in rodents.
The European Chemicals Agency characterized D4 as a persistent, bioaccumulative, and toxic chemical, and designated D4 as a Substance of Very High Concern.
Cyclomethicone 4 may contribute to slippery surfaces if spilled due to its low viscosity and high mobility.
This creates a risk of falls in laboratories or industrial settings.
Floors should be cleaned immediately to restore traction.
Cyclomethicone 4 has low acute toxicity, but systemic effects are possible with repeated high exposure.
Organosiloxanes may accumulate in fatty tissues over time.
Therefore, minimizing unnecessary contact is recommended.
Cyclomethicone 4 can interact with certain plastics and elastomers, causing swelling or material deformation.
This may compromise seals, hoses, or gaskets during equipment use.
Incompatible materials should be replaced with silicone-resistant components.
Cyclomethicone 4 is known to be persistent in the environment, degrading slowly in natural conditions.
Widespread release may increase long-term exposure to aquatic organisms.
Waste must be managed according to environmental regulations to prevent contamination.
