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Basic Information
Product Name: Octamethylcyclotetrasiloxane
CAS Number: 556-67-2
Alias: D4, Cyclotetrasiloxane octamethyl
Chemical Full Name: Octamethyl-1,3,5,7-tetracyclotetrasiloxane
Molecular Formula: C8H24O4Si4
Molecular Weight: 296.62
EINECS: 209-136-7
Structural Information
- Structure Type: Cyclic organosiloxane (4-membered siloxane ring)
- Structural Features: Four Si-O bonds form a stable eight-membered ring, each silicon atom bonded with two methyl groups; low surface tension, good volatility, excellent compatibility with silicone polymers
- Characteristic: Low viscosity volatile cyclic silicone monomer
Physical & Chemical Properties
- Appearance: Colorless transparent low-viscosity liquid
- Odor: Faint slight silicone odor
- Melting Point: 17–18 °C
- Boiling Point: 175–176 °C
- Flash Point: 63 °C (closed cup)
- Density (20℃): 0.956 g/cm3
- Refractive Index (20℃): 1.396
- Solubility: Insoluble in water; miscible with ethanol, isopropanol, mineral oil, aromatic solvents, silicone oils
- Stability: Stable at room temperature sealed storage; hydrolyzes under strong acid/strong alkali to form linear silanols; polymerizes under catalyst to generate polydimethylsiloxane; inert to most non-polar raw materials
Synthesis & Applications
Production Method
Dimethyldichlorosilane undergoes hydrolysis and cyclization reaction, then rectification separation to obtain high-purity D4.
Main Applications
- Silicone polymer monomer: Raw material for polymerization of dimethyl silicone oil, silicone rubber, silicone resin
- Cosmetic raw material: Volatile carrier for skin care cream, hair care essence, makeup base, quick dry without greasy residue
- Daily chemical auxiliary: Lubricant and smoothing agent for shampoo, body wash
- Industrial additive: Release agent, lubricant for plastic, rubber, textile softener
- Electronic chemical auxiliary: Low-viscosity cleaning solvent for precision components
Safety & Storage Instructions
GHS Hazard Classification
- H226 Flammable liquid and vapor
- H315 Causes skin irritation
- H319 Causes serious eye irritation
- H335 May cause respiratory irritation
Personal Protection
Organic vapor respirator, chemical splash goggles, oil-resistant nitrile gloves; operate in ventilated workshop, far away from open flame and static electricity.
Storage Condition
Hermetically sealed iron drum, cool dry ventilated warehouse below 30℃; isolate oxidants, strong acid and alkali.
Transportation
Class 3 weakly flammable organic liquid; avoid sunlight exposure and high temperature during transit.
Quality Specifications
- Purity (GC): ≥99.5%
- Moisture: ≤0.01%
- Chroma (Pt-Co): ≤10
- Total volatile impurities: ≤0.5%
Information Summary Table
| Item | Specification |
| CAS Number | 556-67-2 |
| Product Name | Octamethylcyclotetrasiloxane (D4) |
| Synonym | D4, Octamethyl cyclotetrasiloxane |
| Molecular Formula | C8H24O4Si4 |
| Molecular Weight | 296.62 |
| Appearance | Colorless transparent volatile liquid |
| Flash Point | 63℃ |
| Core Advantage | Volatile, low greasy, basic silicone monomer |
| Storage Rule | Sealed cool ventilated storage, away from fire source |
| Hazard Property | Weakly flammable liquid, mild skin/eye irritant |
| Main Usage | Silicone polymerization monomer, cosmetic volatile raw material, textile softener |
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