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Chemical Name: Hexamethyldisiloxane
CAS Number: 107-46-0
Common Synonyms: HMDSO, Bis(trimethylsilyl) ether
Appearance: Colorless, volatile liquid, mild odor
Recommended Uses: Chemical intermediate, solvent for electronics and pharmaceutical preparation, surface treatment agent
Main Hazards: Highly flammable liquid and vapor; vapor may cause drowsiness or dizziness
Physical Hazards: Can form explosive mixtures with air; frequent ignition sources include open flames or static discharge
Health Hazards: Inhalation can irritate nose, throat, and respiratory tract, sometimes producing headache, nausea, or lightheadedness; skin or eye contact may cause mild irritation
Pictograms (Globally Harmonized System): Flame, Exclamation Mark
Precautionary Measures: Keep away from heat, sparks, open flame; avoid breathing vapors; use only outdoors or in well-ventilated area
Main Component: Hexamethyldisiloxane: approximately 99% by weight
Impurities: Low-level siloxanes or trimethylsilanol, unlikely to be significant for most users
Occupational Limits: Not established by OSHA or ACGIH for this specific compound
Inhalation: Remove person to fresh air immediately; seek medical advice if symptoms persist, such as cough or shortness of breath
Skin Contact: Wash area with soap and water; take off contaminated clothing; if irritation appears, consult a physician
Eye Contact: Rinse cautiously with water for at least several minutes; remove contact lenses if present; continue rinsing; get medical attention if symptoms remain
Ingestion: Do not induce vomiting; rinse mouth thoroughly; seek prompt medical evaluation
Suitable Extinguishing Media: Alcohol-resistant foam, dry chemical, carbon dioxide; water mist works for cooling containers only
Fire-Specific Hazards: Vapors are heavier than air, can spread across floors and ignite at a distance
Special Protective Equipment: Firefighters wear self-contained breathing apparatus and protective clothing to avoid exposure to fumes
Hazardous Combustion Products: Carbon oxides, silicon oxides; combustion can yield irritating or toxic gases
Personal Precautions: Eliminate ignition sources, ventilate area, avoid direct contact with liquid, wear suitable protective gear
Environmental Precautions: Prevent run-off into sewers, surface waters, or soil;
Containment and Clean Up: Use inert absorbents like sand to soak up spill, place in labeled waste containers, ventilate affected area thoroughly
Handling: Ground and bond containers when transferring product, avoid formation of static electricity, do not breathe vapors, wash hands after use
Storage: Store in tightly closed containers, keep away from ignition sources, store in a cool, well-ventilated area, keep out of direct sunlight
Separation: Store away from incompatible materials such as strong oxidizers and acids
Engineering Controls: Use adequate local exhaust ventilation or process enclosures to limit worker exposure
Personal Protection: Wear chemical splash goggles, nitrile gloves, lab coat or protective clothing, and in case of high vapor concentrations, use a suitable respirator
Hygiene Measures: Do not eat, drink, or smoke during handling; wash hands and face thoroughly after use
Form: Liquid
Color: Clear, colorless
Odor: Mild, ether-like
Boiling Point: About 101–102°C
Melting Point: Near -59°C
Vapor Pressure: Moderate, around 50 mmHg at 25°C
Solubility: Practically insoluble in water, miscible with most organic solvents
Flash Point: Roughly 12°C (closed cup)
Density: Approximately 0.76 g/cm³
Chemical Stability: Stable under recommended storage conditions, no significant tendency to decompose unless heated
Reactivity: Reacts vigorously with strong oxidizers, acids, and bases; spontaneous combustion can occur with certain oxidizing materials
Hazardous Decomposition: Burning can form toxic compounds such as formaldehyde, silicon oxides, and carbon monoxide
Acute Effects: High vapor concentrations irritate eyes, nose, and respiratory tract; can cause headaches or dizziness
Chronic Exposure: Prolonged or repeated skin contact may defat skin, leading to dryness or cracking
Sensitization: Not known to cause allergic reactions
Animal Data: Low acute toxicity by oral or dermal routes in laboratory animals
Carcinogenicity: Not classified as a carcinogen by IARC, OSHA, or ACGIH
Ecotoxicity: Low toxicity to aquatic life based on available data; not expected to bioaccumulate significantly
Persistence and Degradability: Breaks down slowly in the environment, tends to volatilize from soil and water surfaces
Mobility: Moves readily in the environment due to volatility; unlikely to contaminate groundwater under usual conditions
Safe Disposal: Incineration in an approved facility offers the most reliable route; follow national and local regulations for hazardous waste
Containers: Empty containers can retain residues and vapors; puncture and triple rinse before disposal or recycling
Shipping Classification: Considered flammable liquid for transport regulations
Packing Instructions: Use approved containers; keep secure during transport to avoid spills or leaks
Hazards: Marked with standard flammable liquid placards when shipping by road, rail, air, or sea
Occupational Safety: Not specifically regulated by OSHA, but general duty to protect worker health and safety applies
Environmental Laws: May appear on some regional inventories such as TSCA in the United States
Labeling: Requires clear hazard statements and proper labeling under GHS and local hazard communication requirements
