CYCLOTETRASILOXANE- ▸ Silicone intermediate: Monomer for manufacture of methyl silicone oils and polymers
- ▸ Carrier solvent: Volatile vehicle and diluent in formulations
- ▸ Emollient: Smooth feel and spreadability in personal care
- ▸ Hair conditioning: Conditioning and antistatic fluid in hair care
A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.
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Transport classification per the UN Model Regulations / 49 CFR 172.101 Hazardous Materials Table. Confirm against the grade-specific SDS (Section 14) before shipping.
Octamethylcyclotetrasiloxane (D4, CAS 556-67-2), a volatile cyclic dimethylsiloxane. Industry references record use in the preparation of methyl silicone oils and as a solvent, diluent, and cosmetic emollient and conditioning fluid. Supplied as a clear, low-viscosity liquid.
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 209-136-7
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Regulatory restriction status
Octamethylcyclotetrasiloxane (Cyclotetrasiloxane, D4) (CAS 556-67-2) appears on the regulatory list(s) below. This is public regulatory information about the substance — not a statement about any specific supplier’s material, and not a safety claim. Confirm the current status for your jurisdiction and intended use.
- REACH SVHC Candidate List (EU): listed 27 Jun 2018 on the basis of PBT (Art. 57(d)), vPvB (Art. 57(e)). SVHC status triggers EU supplier-communication and notification duties above 0.1% w/w; it is not, by itself, a ban on sale.
Sources: ECHA Candidate List / Annex XIV / Annex XVII (echa.europa.eu); U.S. EPA TSCA; UN Stockholm Convention / EU POPs Regulation; California OEHHA Proposition 65 list. Retrieved 2026-07-13.
Frequently Asked Questions
What is cyclotetrasiloxane (D4) used for?
Octamethylcyclotetrasiloxane (D4, CAS 556-67-2) is a volatile cyclic dimethylsiloxane used primarily as a monomer in the manufacture of methyl silicone oils and polymers. It also serves as a volatile carrier solvent and diluent, an emollient for smooth feel and spreadability, and a conditioning/antistatic fluid in hair care.
What is cyclotetrasiloxane made from, and what is its CAS number?
D4 is octamethylcyclotetrasiloxane, a four-unit cyclic dimethylsiloxane with formula C8H24O4Si4 and CAS 556-67-2. It is produced from the hydrolysis and cyclization of dimethyldichlorosilane and is itself a key building block for making silicone polymers. Identity and grade are confirmed on the CoA.
Is cyclotetrasiloxane water soluble?
No. D4 is a low-viscosity silicone liquid that is not water soluble; it is miscible with other silicones and nonpolar solvents, which supports its use as a carrier and polymer feedstock. See the product SDS for full solubility and handling data.
What is the difference between D4, D5, and D6 cyclic siloxanes?
They differ in ring size: D4 (cyclotetrasiloxane) has four siloxane units, D5 five, and D6 six. Increasing ring size raises boiling point and lowers volatility, so D4 is the most volatile of the three. D4 is most often used as a polymerization monomer, while D5 and D6 are more common as personal-care carriers.
What is the cost of bulk cyclotetrasiloxane (D4)?
Bulk D4 pricing depends on grade, packaging, order volume, and destination and is quoted per order rather than listed. Submit a bulk RFQ with your quantity and spec and RawSource will return current pricing with CoA and SDS, classified under HS code 2931.90.
What is the REACH and TSCA regulatory status of Octamethylcyclotetrasiloxane (Cyclotetrasiloxane, D4)?
Octamethylcyclotetrasiloxane (Cyclotetrasiloxane, D4) (CAS 556-67-2) is subject to U.S. TSCA Inventory requirements; supplying it into the EU requires valid REACH registration ((EC) No 1907/2006). RawSource cannot verify a third-party supplier's registrations — buyers should require documented TSCA and REACH compliance for their jurisdiction and volume (EC 209-136-7).