Alpha-Methylstyrene

1Identification

Name

Alpha-Methylstyrene

IUPAC name

prop-1-en-2-ylbenzene

CAS number

98-83-9

EC number

202-705-0

Molecular formula

C9H10

Molecular weight

118.18 g/mol

InChIKey

XYLMUPLGERFSHI-UHFFFAOYSA-N

SMILES

CC(=C)C1=CC=CC=C1

PubChem CID

7407

Synonyms

alpha-Methylstyrene, 2-Phenylpropene, 2-Phenyl-1-propene, 2-Phenylpropylene, Benzene, (1-methylethenyl)-, 1-Methyl-1-phenylethylene, alpha-Methylstyrol, 1-Phenyl-1-methylethylene, beta-Phenylpropylene, 1-Methyl-1-phenylethene, beta-Phenylpropene, ALPHA-METHYL STYRENE, 1-Propene, 2-phenyl-, 2-Phenyl-2-propene

Recommended uses

• Used as a polymerization monomer; [ACGIH]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Polymerization monomer, especially for polyesters
  Hazardous Substances Data Bank (HSDB)
• USED AS A THIRD MONOMER TO RAISE THE GLASS TRANSITION TEMPERATURE IN ACRYLONITRILE-BUTADIENE-STYRENE RUBBER-THERMOPLASTIC RESIN.
  Hazardous Substances Data Bank (HSDB)
• Intermediate Heat stabilizer Hardener Adhesion/cohesion promoter Filler Not Known or Reasonably Ascertainable Monomers Chain transfer agent Solvent
  EPA Chemical Data Reporting (CDR)
• Sizing agent Chain transfer agent Monomers Filler Not Known or Reasonably Ascertainable Adhesion/cohesion promoter Hardener Heat stabilizer
  EPA Chemical Data Reporting (CDR)

Description

• α-Methyl styrene (alpha-Methylstyrene) can cause cancer and female reproductive toxicity according to California Labor Code.
  California Office of Environmental Health Hazard Assessment (OEHHA)
• Isopropenylbenzene appears as a colorless liquid. Insoluble in water and less dense than water. Flash point 115 °F. May be mildly toxic by ingestion, inhalation and skin absorption. Vapors may be narcotic by inhalation. Used as a solvent and to make other chemicals.
  CAMEO Chemicals
• Alpha-Methylstyrene is an olefinic compound.
  ChEBI

2Hazard identification

Signal word

Warning

Pictograms

GHS02, GHS07, GHS09

Classification source

Regulation (EC) No 1272/2008 of the European Parliament and of the Council

Precautionary statements

Other reported classifications

7 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

NFPA 704 rating

• 1 - Materials that, under emergency conditions, can cause significant irritation.
  Hazardous Substances Data Bank (HSDB)
• 2 - Materials that must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur. Materials would not under normal conditions form hazardous atmospheres with air, but under high ambient temperatures or under moderate heating could release vapor in sufficient quantities to produce hazardous atmospheres with air.
  Hazardous Substances Data Bank (HSDB)
• 1 - Materials that in themselves are normally stable but that can become unstable at elevated temperatures and pressures.
  Hazardous Substances Data Bank (HSDB)

Health hazards

• Inhalation causes irritation of respiratory tract, headache, dizziness, light-headedness, and breathlessness. Ingestion causes irritation of mouth and stomach. Contact with liquid irritates eyes. Prolonged skin contact can cause severe rashes, swelling, and blistering. (USCG, 1999)
  CAMEO Chemicals
• CAUTION: Petroleum crude oil (UN1267) may contain TOXIC hydrogen sulphide gas. · Inhalation or contact with material may irritate or burn skin and eyes. · Fire may produce irritating, corrosive and/or toxic gases. · Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas. · Runoff from fire control or dilution water may cause environmental contamination.
  Emergency Response Guidebook (ERG)

Fire hazards

• Excerpt from ERG Guide 128 [Flammable Liquids (Water-Immiscible)]: HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air. Vapors may travel to source of ignition and flash back. Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.). Vapor explosion hazard indoors, outdoors or in sewers. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Runoff to sewer may create fire or explosion hazard. Containers may explode when heated. Many liquids will float on water. Substance may be transported hot.
  CAMEO Chemicals
• · HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. · Vapors may form explosive mixtures with air. · Vapors may travel to source of ignition and flash back. · Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.). · Vapor explosion hazard indoors, outdoors or in sewers. · Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. · Runoff to sewer may create fire or explosion hazard. · Containers may explode when heated. · Many liquids will float on water. · Substance may be transported hot.
  Emergency Response Guidebook (ERG)
• Flammable. Above 54 °C explosive vapour/air mixtures may be formed.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• Human subjects complained of an unpleasant odor and mild eye irritation. CNS depression possible after absorption of sufficient dose; TLV Basis: Irritation; Kidney & female reproductive damage; [ACGIH] A lachrymator; [CHEMINFO] A skin, eye, and respiratory tract irritant; Causes lachrymation; [ICSC]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• The major hazards encountered in the use and handling of alpha-methyl styrene stem from its toxicologic properties and flammability. Toxic by all routes (ie, inhalation, ingestion, and dermal contact), exposure to this sweet-smelling, colorless liquid may occur from its use in the manufacture of acrylonitrile-butadiene-styrene resins, adhesives, waxes, and polyester resins. Effects from exposure may include irritation of the eyes, skin, and upper respiratory tract, dermatitis, and central nervous system depression.
  Hazardous Substances Data Bank (HSDB)

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop. SKIN: IMMEDIATELY flood affected skin with water while removing and isolating all contaminated clothing. Gently wash all affected skin areas thoroughly with soap and water.
  CAMEO Chemicals
• General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped with a one-way valve or other device).
  Emergency Response Guidebook (ERG)
• (General first aid procedures) Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Water flush promptly - If this chemical contacts the skin, flush the contaminated skin with water promptly. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water promptly. If irritation persists after washing, get medical attention. Breathing: Respiratory support Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately.
  The National Institute for Occupational Safety and Health (NIOSH)

Symptoms of exposure

• Cough. Dizziness. Sore throat.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Watering of the eyes.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

Not available in the public sources we compile. Check Section 5 of the supplier's SDS.

Hazardous combustion products

• When heated to decomposition, it emits acrid smoke & fumes.
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 128 [Flammable Liquids (Water-Immiscible)]: IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 50 meters (150 feet) in all directions. LARGE SPILL: Consider initial downwind evacuation for at least 300 meters (1000 feet). FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)
  CAMEO Chemicals
• Immediate precautionary measure · Isolate spill or leak area for at least 50 meters (150 feet) in all directions. Large Spill · Consider initial downwind evacuation for at least 300 meters (1000 feet). Fire · If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions.
  Emergency Response Guidebook (ERG)

Spill cleanup

• Personal protection: filter respirator for organic gases and vapours adapted to the airborne concentration of the substance. Do NOT let this chemical enter the environment. Ventilation. Collect leaking and spilled liquid in sealable non-metallic containers as far as possible. Absorb remaining liquid in sand or inert absorbent. Then store and dispose of according to local regulations.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• For spills & leakage absorb on paper. Evaporate on a glass or iron dish in hood. Burn the paper.
  Hazardous Substances Data Bank (HSDB)

7Handling and storage

• Store only if stabilized. Store in an area without drain or sewer access. Fireproof. Well closed. Separated from strong oxidants.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• DURING STORAGE IT IS FREQUENTLY STABILIZED WITH TERT-BUTYL CATECHOL AS INHIBITOR.
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for alpha-Methyl styrene: Skin: PREVENT SKIN CONTACT - Wear appropriate personal protective clothing to prevent skin contact. Eyes: PREVENT EYE CONTACT - Wear appropriate eye protection to prevent eye contact. Wash skin: WHEN CONTAMINATED - The worker should immediately wash the skin when it becomes contaminated. Remove: WHEN WET OR CONTAMINATED - Work clothing that becomes wet or significantly contaminated should be removed and replaced. Change: No recommendation is made specifying the need for the worker to change clothing after the workshift. (NIOSH, 2024)
  CAMEO Chemicals
• Wear appropriate personal protective clothing to prevent skin contact.
  Hazardous Substances Data Bank (HSDB)
• Wear appropriate eye protection to prevent eye contact.
  Hazardous Substances Data Bank (HSDB)
• Recommendations for respirator selection. Max concn for use: 500 ppm. Respirator Class(es): Any chemical cartridge respirator with organic vapor cartridge(s). May require eye protection. Any supplied-air respirator. May require eye protection.
  Hazardous Substances Data Bank (HSDB)

Respirator recommendations

• NIOSH Up to 500 ppm: (APF = 10) Any chemical cartridge respirator with organic vapor cartridge(s)* (APF = 10) Any supplied-air respirator* Up to 700 ppm: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode* (APF = 50) Any chemical cartridge respirator with a full facepiece and organic vapor cartridge(s) (APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister (APF = 25) Any powered, air-purifying respirator with organic vapor cartridge(s)* (APF = 50) Any self-contained breathing apparatus with a full facepiece (APF = 50) Any supplied-air respirator with a full facepiece Emergency or planned entry…
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• ISOPROPENYLBENZENE is easily peroxidizable; the peroxide may initiate exothermic polymerization of the bulk material. Reacts violently with strong oxidizing agents [Handling Chemicals Safely, 1980 p. 866; Bretherick, 1979 p. 160].
  CAMEO Chemicals
• Flammable. Oxidizes readily in air to form unstable peroxides that may explode spontaneously [Bretherick, 1979 p.151-154, 164]. Insoluble in water.
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Oxidizers, peroxides, halogens, catalysts for vinyl or ionic polymers; aluminum, iron chloride, copper [Note: Usually contains an inhibitor such as tert-butyl catechol].
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Target organs

• Eyes, skin, respiratory system, central nervous system
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• The substance is irritating to the eyes, skin and respiratory tract. Lachrymation.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• Repeated or prolonged contact with skin may cause dermatitis.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN number: UN 2303

Shipping name

• UN 2303; Isopropenylbenzene
  Hazardous Substances Data Bank (HSDB)
• IMO 3.3; Isopropenylbenzene
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Isopropenylbenzene
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• UN2303
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Class 3 Flammable and combustible liquid (49 eCFR § 173.120)
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172

DOT label

• Flammable Liquid
  CAMEO Chemicals

UN classification

• UN Hazard Class: 3; UN Pack Group: III
  ILO-WHO International Chemical Safety Cards (ICSCs)

Emergency Response Guidebook

• 2303 128
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

• This action promulgates standards of performance for equipment leaks of Volatile Organic Compounds (VOC) in the Synthetic Organic Chemical Manufacturing Industry (SOCMI). The intended effect of these standards is to require all newly constructed, modified, and reconstructed SOCMI process units to use the best demonstrated system of continuous emission reduction for equipment leaks of VOC, considering costs, non air quality health and environmental impact and energy requirements. alpha-Methylstyrene is produced, as an intermediate or a final product, by process units covered under this subpart.
  Hazardous Substances Data Bank (HSDB)
• Pursuant to section 8(d) of TSCA, EPA promulgated a model Health and Safety Data Reporting Rule. The section 8(d) model rule requires manufacturers, importers, and processors of listed chemical substances and mixtures to submit to EPA copies and lists of unpublished health and safety studies. Benzene, (1-methylethenyl)- is included on this list.
  Hazardous Substances Data Bank (HSDB)

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 7407 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.