Material Safety Data Sheet: Octamethylcyclotetrasiloxane

Identification

Product Name: Octamethylcyclotetrasiloxane
Chemical Name: Octamethylcyclotetrasiloxane
Synonyms: D4, OMCTS
Chemical Formula: C8H24O4Si4
CAS Number: 556-67-2
Manufacturer: Commercial and specialty chemical producers of silicone-based products worldwide
Recommended Use: Used as an intermediate in silicone polymer production, cosmetic formulations, industrial lubricant bases, antifoaming agents, and personal care applications
Emergency Contact: Refer to chemical supplier or local poison control resource

Hazard Identification

Classification: Flammable liquids (Category 4), Aquatic Chronic (Category 2), Eye irritation (Category 2B), Skin irritation (Category 2), Aspiration hazard (Category 1)
Signal Word: Warning
Hazard Statements: May cause skin and eye irritation, Harmful if inhaled, Suspected of damaging fertility, Harmful to aquatic life with long-lasting effects, Combustible liquid
GHS Pictograms: Exclamation mark, Health hazard, Environmental hazard
Precautionary Statements: Avoid breathing vapors, Wash hands thoroughly after handling, Avoid release to the environment, Wear protective gloves, clothing, and eye protection, Response in case of accidental exposure described in First Aid Measures

Composition / Information on Ingredients

Chemical Name: Octamethylcyclotetrasiloxane
Concentration: > 99%
CAS Number: 556-67-2
Other Components: Trace levels of impurities such as hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, typically present in quantities < 1%

First Aid Measures

Inhalation: Move to fresh air, keep individual comfortable, support breathing as needed, seek medical attention for symptoms such as cough, headache, or difficulty breathing
Skin Contact: Remove contaminated clothing, wash affected area with soap and water, seek medical advice if irritation persists
Eye Contact: Rinse cautiously with water for at least 15 minutes, remove contact lenses if present and easy to do, continue rinsing, consult a healthcare provider
Ingestion: Rinse mouth, do not induce vomiting, seek immediate medical attention
Note to Physicians: Symptomatic and supportive treatment, monitor for chemical pneumonitis if aspiration suspected

Fire-Fighting Measures

Suitable Extinguishing Media: Carbon dioxide, dry chemical powder, foam, water spray
Unsuitable Extinguishing Media: Water jet may spread liquid fire
Special Hazards: Vapors may form explosive mixtures with air, combustible at higher temperatures, thermal decomposition releases toxic gases such as formaldehyde, carbon monoxide, and silicon oxides
Protective Equipment: Wear self-contained breathing apparatus, full protective gear for chemical fires
Fire-Fighting Instructions: Keep containers cool with water spray, control runoff to prevent chemical from entering water courses

Accidental Release Measures

Personal Precautions: Isolate area and restrict unnecessary entry, ventilate area, avoid vapor inhalation, wear suitable personal protective equipment
Environmental Precautions: Prevent further leakage or spillage if safe, avoid discharge to drains or waterways, notify authorities in case of large spills
Methods for Clean-Up: Absorb spill with inert materials such as sand, collect into properly labeled nonmetallic containers, clean area with detergent and water, ventilate well, dispose of collected material in accordance with local regulations

Handling and Storage

Handling: Use only in well-ventilated areas, avoid contact with skin, eyes, and clothing, prevent formation of vapors or aerosols, ground/bond containers and equipment, wash thoroughly after handling
Storage: Keep containers tightly closed in a cool, dry, well-ventilated location away from ignition sources and incompatible materials such as strong acids and oxidizers, store in containers made of compatible materials such as stainless steel or HDPE, keep away from food and animal feed

Exposure Controls and Personal Protection

Engineering Controls: Use process enclosures, local exhaust ventilation or other engineering controls to maintain airborne levels below permissible limits, provide eyewash and safety shower stations nearby
Control Parameters: Occupational exposure limits may vary by country; example: ACGIH TLV not established, manufacturer-recommended exposure limit: 10 ppm TWA
Personal Protective Equipment: Respiratory protection if vapor concentrations approach threshold limits (organic vapor cartridge mask), chemical-resistant gloves (nitrile, neoprene), splash goggles or face shield, flame-retardant clothing, chemical-resistant shoes
Hygiene Measures: Wash hands, arms, and face thoroughly before eating, drinking, or smoking, avoid wearing contaminated clothing outside the workplace

Physical and Chemical Properties

Appearance: Clear, colorless liquid
Odor: Mild characteristic odor
Melting Point: 16 – 19°C
Boiling Point: 175 – 177°C
Density: 0.95 g/cm³ at 25°C
Vapor Pressure: 0.13 kPa at 25°C
Solubility: Insoluble in water, soluble in organic solvents such as benzene, toluene
pH: Not applicable
Viscosity: 2.5 mm²/s (cSt) at 25°C
Flash Point: 77°C (closed cup)
Autoignition Temperature: 400°C
Explosive Properties: Can form explosive vapor/air mixtures above flash point
Partition Coefficient (log Kow): About 6.5

Stability and Reactivity

Chemical Stability: Stable under normal conditions of handling and storage
Reactivity: Inert to most materials, reacts with strong oxidizing agents, acids, or alkalis, decomposes when heated above 200°C to yield hazardous products
Hazardous Decomposition Products: Silica, formaldehyde, carbon monoxide, carbon dioxide, silicon oxides
Polymerization: Not known to occur under normal conditions

Toxicological Information

Acute Toxicity: Oral LD50 (rat): > 4800 mg/kg, Dermal LD50 (rabbit): > 2400 mg/kg, Inhalation LC50 (rat, 4h): > 36 mg/L
Skin Corrosion/Irritation: Mild irritant
Serious Eye Damage/Irritation: Mild irritant
Respiratory Sensitization: Not classified as a respiratory sensitizer
Carcinogenicity: Evidence in laboratory animals but relevance for humans debated, not listed as a known human carcinogen by IARC, NTP, or OSHA
Reproductive Toxicity: Some data shows concern for reproductive effects and hormonal disruption in animal studies
Route of Exposure: Inhalation, ingestion, skin and eye contact
Repeated Exposure: Prolonged inhalation may affect the liver, uterus, and reproductive organs, particularly in animal models

Ecological Information

Ecotoxicity: Harmful to aquatic life with long-lasting effects, acute LC50 (fish): 10 – 100 mg/L, LC50 (daphnia): 15 mg/L
Persistence and Degradability: Not readily biodegradable, has potential to bioaccumulate in aquatic environments
Bioaccumulative Potential: High
Mobility in Soil: Low mobility, tends to adsorb strongly to soil organic matter
Other Adverse Effects: Possible endocrine disruption in aquatic organisms observed in some studies

Disposal Considerations

Waste Treatment Methods: Incinerate in a chemical incinerator equipped with afterburner and scrubber, contact licensed waste disposal contractors
Container Disposal: Rinse thoroughly, dispose of according to local regulations, prevent release to the environment, do not allow material to enter watercourses
Special Precautions: Keep out of reach of children, do not reuse or refill empty containers except as directed

Transport Information

UN Number: Not classified as hazardous for transportation under most international regulations
Proper Shipping Name: Octamethylcyclotetrasiloxane
Transport Hazard Class: Not regulated as a dangerous good, but local regulations may apply
Packing Group: Not applicable
Environmental Hazards: Harmful to aquatic environments, take precautions to prevent leaks during shipment
Special Transport Precautions: Protect containers from physical damage, keep away from food, advise carriers regarding chemical nature and risks in case of spillage

Regulatory Information

National Inventory Status: Listed on TSCA (US), EINECS (EU), DSL (Canada), AICS (Australia), ENCS (Japan)
SARA Title III (Sections 311/312): Immediate (acute) health hazard, Delayed (chronic) health hazard
California Proposition 65: Not listed
OSHA Status: Regulated for safe handling, personal protection, hazard communication required
REACH Status (EU): Substances subject to certain restrictions due to concerns for persistence, bioaccumulation, and toxicity
Transport Regulations: Not regulated as a restricted material for ground, air, or sea, but regional controls may designate as environmentally hazardous
Labeling Requirements: GHS-compliant hazard statements and pictograms on all storage and handling containers