Product Name: Hexamethyldisiloxane
Chemical Formula: C6H18OSi2
Synonyms: Bis(trimethylsilyl) ether
CAS Number: 107-46-0
Recommended Use: Solvent, chemical intermediate
Manufacturer: Major chemical suppliers within North America, Europe, and Asia manage distribution. Contact addresses and emergency numbers usually stay printed on containers or bills of lading for rapid access.
Classification: Flammable Liquid, Category 2
Signal Word: Danger
Hazard Statements: Highly flammable liquid and vapor. Vapors may cause drowsiness or dizziness. May cause mild skin irritation.
Pictograms: Flame, Exclamation mark
Precautionary Statements: Keep container tightly closed. Store away from heat, sparks, open flames, or hot surfaces. Avoid breathing vapor. Use only outdoors or in well-ventilated area. Wear protective gloves and eye/face protection.
Substance: Hexamethyldisiloxane
CAS Number: 107-46-0
Purity: More than 99% by weight
Impurities: Trace levels of other siloxanes may be present, usually under strict quality controls.
Inhalation: Remove individual to fresh air, keep comfortable for breathing. Give oxygen or seek medical help if symptoms persist.
Skin Contact: Immediately remove contaminated clothing. Wash exposed area with soap and plenty of water. Persistent irritation calls for medical attention.
Eye Contact: Rinse cautiously with water for several minutes, holding eyelids open. Remove contact lenses if present and continue rinsing. Seek immediate medical help for severe or lasting symptoms.
Ingestion: Do not induce vomiting. Rinse mouth thoroughly. Contact a poison center or physician at once.
Suitable Extinguishing Media: Dry chemical, foam, carbon dioxide, or water spray for large fires. Use water fog to cool containers.
Unsuitable Media: Full water streams could spread flammable liquid.
Hazardous Combustion Products: Carbon oxides, silicon oxides, and possibly traces of formaldehyde.
Special Protective Actions: Firefighters wear self-contained breathing apparatus and full protective clothing.
Special Hazards: Vapors may form explosive mixtures with air. Containers exposed to fire heat risk bursting by pressure build-up.
Personal Precautions: Evacuate unnecessary personnel. Ventilate area. Eliminate all ignition sources. Prevent inhalation of vapors.
Environmental Precautions: Prevent entry into drains, waterways, or soil. Notify authorities if substantial spillage may affect the environment.
Containment and Cleaning Up: Dike and absorb spill with earth, sand, or suitable inert absorbent. Shovel up and place in a chemical waste container for proper disposal. Wash area with water and ventilate.
Safe Handling: Use in areas with adequate ventilation. Ground all equipment during handling. Open slowly to control any pressure build-up.
Storage Conditions: Store in tightly closed containers in a cool, dry, well-ventilated place away from ignition sources and incompatible materials like oxidizers or acids. Use bonding/grounding to prevent static discharge.
Incompatibilities: Strong oxidizing agents, acids, and some plastics, which may degrade or embrittle upon exposure.
Exposure Limits: No OSHA or ACGIH exposure limit defined, though employer-level policies often reflect solvent exposure strategies.
Engineering Controls: Local exhaust and general ventilation reduce vapor concentrations. Emergency showers and eyewash stations help limit injury.
Eye Protection: Safety goggles or face shields when splashing risk is expected.
Skin Protection: Impervious gloves, lab coats, or overalls needed.
Respiratory Protection: Respirators with organic vapor cartridges may be required during high-concentration operations or accidental releases.
Appearance: Clear, colorless liquid
Odor: Slightly ether-like aroma
Odor Threshold: Not available
pH: Not applicable
Melting Point: Around -59°C (-74°F)
Boiling Point: ~101°C (214°F)
Flash Point: 12°C (54°F) closed cup
Evaporation Rate: Rapid
Flammability: Highly flammable
Explosion Limits: Lower 0.9%; Upper 13% (v/v in air)
Vapor Pressure: 55 mmHg at 25°C
Vapor Density: About 5 (Air = 1)
Relative Density: 0.76 g/cm³ at 25°C
Solubility: Insoluble in water; miscible with organic solvents
Partition Coefficient (n-Octanol/Water): log Kow 3.5–4.2
Auto-ignition Temperature: 250°C (482°F)
Decomposition Temperature: Not specified
Viscosity: 0.65 mPa·s at 25°C
Chemical Stability: Remains stable under expected storage and handling conditions. Instability may begin with exposure to strong acids, oxidizers, or heat.
Conditions to Avoid: High temperatures, open flames, electrostatic charges.
Incompatible Materials: Strong acids, bases, oxidizing agents.
Hazardous Decomposition Products: Silicon oxides, carbon oxides, and small amounts of formaldehyde.
Polymerization: Does not undergo polymerization under normal conditions.
Acute Toxicity (Oral, Rat): LD50 > 4000 mg/kg
Dermal Toxicity: Not expected to be highly toxic, but may cause mild skin irritation.
Inhalation: High vapor concentrations can cause irritation of respiratory tract, drowsiness, or dizziness.
Skin Corrosion/Irritation: Prolonged contact may produce dryness or cracking.
Eye Damage/Irritation: Vapor or liquid contact produces mild irritation.
Chronic Effects: No strong evidence of long-term toxicity. No data for carcinogenicity, reproductive, or mutagenic effects under standard exposure scenarios.
Toxicity: Toxic to aquatic organisms. LC50 (fish) estimated in tens of mg/L range. Persistence in water unlikely due to volatilization.
Persistence and Degradability: Tends to break down by hydrolysis and evaporation. Not regarded as readily biodegradable; may persist in sediment.
Bioaccumulative Potential: Log Kow values above 3 indicate potential for bioaccumulation, but rapid volatilization from surface waters often limits lasting exposure.
Mobility in Soil: Low water solubility and volatility mean most product lost from soil occurs through evaporation, reducing likelihood of groundwater contamination.
Other Adverse Effects: Avoid discharge into surface waters; spills may threaten aquatic life and disrupt ecosystems.
Waste Disposal Methods: Dispose of contents and container according to local, regional, and national regulations. Incineration under controlled conditions often provides the best outcome if recovery or recycling is not practical.
Contaminated Packaging: Empty containers may contain hazardous residues and require triple rinsing or professional cleaning before recycling or disposal.
Special Procedures: Never allow product to enter natural water bodies, stormwater systems, or untreated municipal landfills.
UN Number: UN1993
Proper Shipping Name: Flammable Liquid, n.o.s. (Hexamethyldisiloxane)
Transport Hazard Class: 3 (Flammable liquids)
Packing Group: II
Labels: Flammable liquid
Special Precautions: Handle containers carefully in transit. Avoid transport near hooded or open ignition sources.
Environmental Hazards: Marine pollutant regulations may apply. Spill response plans stay needed in case of transportation release incidents.
U.S. Regulations: Listed on TSCA inventory. Subject to SARA Title III, Section 311/312 (acute health, fire hazard). OSHA hazardous chemical as defined by 29 CFR 1910.1200.
EU Regulations: Covered under REACH as a registered substance. Classified F, Xi under Dangerous Substances Directive.
International Regulations: Included on Australia AICS, Canadian DSL, Japanese ENCS, Chinese IECSC. Hazard and transport classes recognized by UN GHS.
Specific Provisions: Require use of safety data sheets in workplace settings. Employee training and risk management measures stay part of ongoing compliance.
