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    Related: Silicone Intermediate Vinyl Silicone Oil Trimethylchlorosilane
    • Octamethylcyclotetrasiloxane D4 CAS 556-67-2

    Octamethylcyclotetrasiloxane D4 CAS 556-67-2

    Octamethylcyclotetrasiloxane, commonly called D4, CAS 556-67-2, is a cyclic dimethylsiloxane tetramer supplied as a silicone monomer and feedstock. Confirm the required grade and specification, then request a quotation with COA/TDS/SDS for bulk supply.

    • CAS: 556-67-2
    • Synonyms: D4, OMCTS, Cyclic dimethylsiloxane tetramer, 2,2,4,4,6,6,8,8-Octamethylcyclotetrasiloxane, Cyclotetrasiloxane octamethyl
    • Einecs: 209-136-7
    • Molecular Formula: C₈H₂₄O₄Si₄
    • Grade: Industrial Grade
    • Package: 200 kg drum / 1000 kg IBC (customizable)
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    Product Description

    Octamethylcyclotetrasiloxane, commonly called D4, CAS 556-67-2, is a cyclic dimethylsiloxane tetramer with the molecular formula C8H24O4Si4.

    Synonyms: D4; OMCTS; Cyclic dimethylsiloxane tetramer; 2,2,4,4,6,6,8,8-Octamethylcyclotetrasiloxane; Cyclotetrasiloxane octamethyl.

    CAS: 556-67-2.

    It has the molecular formula C8H24O4Si4 and a molecular weight of 296.62 g/mol.

    It is a colorless, clear, low-viscosity liquid.

    It has a melting/freezing point of about 17 °C and a boiling point of about 175–176 °C.

    It has a density of about 0.95–0.96 g/mL and a closed-cup flash point of about 51–55 °C.

    It has very low water solubility and moderate volatility.

    It is primarily used as a precursor in silicone manufacturing through ring-opening polymerization.

    It is converted into polysiloxane backbones used to make silicone oils, rubbers and resins.

    D4 contains four silicon atoms in its ring, while D5 contains five and D6 contains six.

    This changes molecular weight, boiling point, vapor pressure and end-use behavior.

    It is also used as an industrial process fluid or carrier where silicone compatibility is required.

    D4 is regulated in some consumer and cosmetic applications, especially in the EU; confirm end-use compliance and D4/D5/D6 residue requirements.

    Confirm appearance, purity, water content, residue limits and physical properties.

    Store in tightly sealed containers in a cool, dry, well-ventilated area, away from heat, sparks, open flames and strong oxidizers.

    Confirm packaging with the requested quantity and destination requirements.

    The page is an RFQ entry point and does not state stock, price, MOQ or fixed lead time.

    For an RFQ, state the intended use, required grade and specification, quantity, packaging, destination and document needs.

    FAQ - Technical & Supply Chain

    • Q:

      What is Octamethylcyclotetrasiloxane CAS 556-67-2?

      A: Octamethylcyclotetrasiloxane, commonly called D4, CAS 556-67-2, is a cyclic dimethylsiloxane tetramer with the molecular formula C8H24O4Si4. It is a colorless, low-viscosity liquid used mainly as a silicone monomer and feedstock.
    • Q:

      What is the main industrial use of D4?

      A: D4 is primarily used as a precursor in silicone manufacturing. Through ring-opening polymerization, it is converted into polysiloxane backbones used to make silicone oils, silicone rubbers and silicone resins.
    • Q:

      How does D4 differ from D5 and other cyclic siloxanes?

      A: D4 contains four silicon atoms in its ring, while D5 contains five and D6 contains six. This changes molecular weight, boiling point, vapor pressure and end-use behavior, even though all are cyclic dimethylsiloxanes used in silicone chemistry.
    • Q:

      What are typical physical properties of D4?

      A: D4 is normally a colorless clear liquid with a boiling point of about 175-176 C, freezing point around 17-18 C, density around 0.95-0.96 g/mL, and a closed-cup flash point in the region of 51-60 C. It has very low water solubility and is moderately volatile.
    • Q:

      Are there regulatory considerations for D4?

      A: D4 is regulated in some consumer and cosmetic applications, especially in the EU, because cyclic volatile methyl siloxanes may be persistent or bioaccumulative. Industrial polymer synthesis remains a key use, but buyers should confirm end-use compliance and any D4/D5/D6 residue requirements for their region.

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