α-Methylstyrene (AMS / alpha-Methylstyrene)
Reactive Vinyl Aromatic Monomer · Non-HAP Styrene Alternative · Purity ≥99.5% · AMS Supplier from China · Global Shipping
⚠ Regulatory & Safety Notice - Flammable Monomer · Carc. 2 (H351) · Self-Polymerization Risk
Flammable liquid (flash point 45°C, Class 3 DG): AMS requires explosion-proof electrics, ventilation, and segregation from ignition sources during all storage and handling.
EU CLP Carc. 2 (H351) - verify current classification: α-Methylstyrene carries a suspected carcinogen classification in some EU CLP assessments. Buyers must confirm current status via the ECHA substance information page and obtain a current CLP-compliant SDS before use. AMS is not classified as Repr. 1B and is not on REACH Annex XIV.
Self-polymerization risk: AMS is stabilised with 100–200 ppm TBC (4-tert-butylcatechol) inhibitor. The TBC inhibitor requires dissolved oxygen to function - sealed drums purged of headspace oxygen must be handled with care. Storage at 0–25°C away from heat, light, and initiators is mandatory.
ℹ AMS - Reactive Vinyl Aromatic Monomer, Not a Solvent
Unlike solvents, α-Methylstyrene (AMS) is designed to copolymerise into polymer chains. Its alpha-methyl group on the vinyl double bond (CH₂=C(CH₃)–C₆H₅) raises copolymer glass transition temperature (Tg ~120–145°C vs styrene's ~100°C), provides controlled polymerisation kinetics via its ceiling temperature (~61°C), and delivers thermal degradation resistance. These properties make AMS the global standard heat-resistance upgrade monomer in ABS, SAN, and acrylic resin systems. Inhibitor removal before polymerisation use is required.
What Is α-Methylstyrene (AMS)?
α-Methylstyrene (AMS, CAS 98-83-9), also written as alpha-methylstyrene and systematically named 2-phenyl-1-propene or isopropenylbenzene, is a vinyl aromatic monomer produced industrially as a by-product of cumene oxidation to phenol and acetone - the same process that produces the world's phenol supply. AMS availability and pricing therefore track the global phenol production cycle rather than independent supply-demand dynamics. Complete physicochemical data is available from NCBI PubChem (CID 7955) and the ECHA substance information page.
AMS is a colorless liquid with density 0.909–0.912 g/cm³, boiling point 165.3°C, and flash point 45°C. Its most chemically distinctive property is its ceiling temperature of approximately 61°C - the temperature above which thermodynamic equilibrium favours depolymerisation, preventing AMS from forming high-MW homopolymer under standard free-radical conditions. In practical terms, AMS copolymerises readily with acrylonitrile, MMA, and acrylic acid at 60–80°C but does not homopolymerise at high MW - a property exploited in AMSAN synthesis, end-capping, and controlled oligomer production.
AMS is not a US EPA Hazardous Air Pollutant (HAP) - confirmed by the EPA CompTox Dashboard. This is AMS's primary regulatory advantage over styrene (HAP-listed, Carc. 1B) in US UPR manufacturing, coating production, and adhesive formulation where HAP emission control obligations impose cost and regulatory burden.
AMS contains 100–200 ppm TBC (4-tert-butylcatechol) inhibitor added during production to suppress spontaneous polymerisation. The TBC inhibitor requires dissolved oxygen to function effectively - fully oxygen-depleted AMS in sealed drums provides significantly reduced inhibitor protection. Oxygen control is therefore a critical consideration in AMS storage management and inhibitor removal procedures before polymerisation.
Product Specifications
Sinolook's AMS specification includes monomer-specific parameters - inhibitor content (100–200 ppm TBC), ceiling temperature (~61°C), and storage range (0–25°C) - that reflect AMS's status as a reactive monomer requiring polymerisation inhibition management. Reference data from PubChem CID 7955 and the EPA CompTox Dashboard.
| Parameter | Specification / Value |
|---|---|
| Product Name | α-Methylstyrene (AMS / alpha-Methylstyrene / Isopropenylbenzene / 2-Phenyl-1-propene) |
| CAS Number | 98-83-9 |
| EC Number | 202-705-0 |
| Molecular Formula | C₉H₁₀ |
| Molecular Weight | 118.18 g/mol |
| Appearance | Colorless Transparent Liquid |
| Purity | ≥99.5% |
| Water Content | ≤0.05% |
| Color (Pt-Co) | ≤10 |
| Density (d20) | 0.909–0.912 g/cm³ |
| Boiling Point | 165.3°C (760 mmHg) |
| Flash Point | 45°C (closed cup) - Class 3 Flammable Liquid |
| Refractive Index | 1.538–1.540 (n20/D) |
| Viscosity (20°C) | ~0.98 mPa·s |
| Ceiling Temperature | ~61°C - AMS does not readily homopolymerise above this temperature |
| Inhibitor | 100–200 ppm TBC (4-tert-butylcatechol) - oxygen-dependent; remove before polymerisation |
| EU Repr. Classification | ✓ Not classified (no Repr. 1B) |
| EU Carc. Classification | ⚠ Carc. 2 (H351) - suspected carcinogen; verify current ECHA status |
| REACH Annex XIV | ✓ Not listed |
| US HAP Status | ✓ Not listed (Non-HAP - distinct from styrene which IS HAP-listed) |
| TSCA Inventory | ✓ Listed |
| Packing | 180 KG / Iron Drum (standard); IBC Tank (900 KG) |
| Storage | 0–25°C; sealed metal drums; dark, ventilated; away from heat, initiators & oxidizers; shelf life 6–12 months with inhibitor |
Applications of α-Methylstyrene (AMS)
AMS's global use profile is dominated by heat-resistant copolymer synthesis - particularly ABS and SAN modification for automotive and appliance heat resistance - followed by UPR styrene substitution for HAP compliance, and acrylic coating modification. Its ceiling temperature chemistry enables end-capping and Tg-raising functions that no other commodity vinyl monomer can replicate at comparable cost.
Heat-Resistant ABS & AMSAN Copolymers
Co-monomer in ABS and HIPS to increase heat distortion temperature (HDT) from ~80°C to ~100–105°C. AMS-modified ABS (AMSAN) is the standard heat-resistant grade for automotive interiors, electrical housings, and appliance components exposed to elevated service temperatures.
AMSAN High-Tg Copolymer
Copolymerisation with acrylonitrile produces AMSAN copolymers with Tg up to ~115–125°C - significantly higher than standard SAN (~100°C). Used as the rigid phase in heat-resistant ABS formulations and as a standalone engineering thermoplastic for heat-resistant transparent applications.
Acrylic Resin Coatings - Tg-Raising Co-Monomer
Co-monomer in acrylic emulsion, solution, and UV-cure coating resins to raise film Tg, improve blocking resistance and hardness in architectural, industrial, and wood coating systems. AMS's aromatic ring contributes hydrophobicity and exterior weathering performance.
Unsaturated Polyester Resin - Non-HAP Styrene Substitute
Non-HAP reactive diluent in UPR and vinyl ester resins - partial or full styrene substitute to reduce HAP air emissions. AMS crosslinks the UPR matrix during cure and contributes higher Tg than styrene-crosslinked UPR, improving composite thermal performance.
Tackifier Resins - Hot-Melt & PSA
Monomer in C9 aromatic hydrocarbon tackifier resins and AMS pure monomer resins for hot-melt adhesives (HMA), pressure-sensitive adhesives (PSA), and rubber compounding. AMS-containing tackifiers have higher softening points and better compatibility with SIS/SBS block copolymer elastomers.
Fragrance Intermediates & Specialty Chemistry
Building block for fragrance ingredients (via Diels-Alder reactions), pharmaceutical intermediates, and specialty polymer additives. The aromatic ring and alpha-methyl vinyl functionality enable diverse modification chemistries for fine chemical synthesis.
ABS & AMSAN Resin - The Global Heat-Resistance Standard
The largest global application for alpha-methylstyrene is in the production of heat-resistant ABS and AMSAN (α-methylstyrene-acrylonitrile) copolymers. Standard ABS has a heat distortion temperature (HDT at 1.8 MPa) of approximately 80–90°C - insufficient for automotive interior components subject to solar heat loading, appliance housings near heat-generating components, and electrical enclosures exposed to operating temperatures.
By substituting AMS for styrene as the rigid aromatic phase monomer in the SAN matrix of ABS, manufacturers produce AMS-ABS (AMSAN rubber-modified copolymer) with HDT values of 95–105°C at 1.8 MPa - an increase of approximately 15–20°C over standard ABS with no change in processing conditions or part design. The AMSAN matrix typically contains 20–35% AMS by weight in copolymerisation with acrylonitrile, where the AMS unit's methyl group restricts chain mobility more effectively than the unsubstituted styrene unit, raising the effective Tg of the matrix from ~100°C to ~115–125°C.
In the automotive sector - the dominant market for heat-resistant ABS - AMSAN ABS is specified in instrument panels, console components, A/B/C pillar trim, exterior mirror housings, under-hood clip and bracket assemblies, and HVAC housing components where dimensional stability at 100°C+ is required by OEM specifications. Sinolook's purity ≥99.5% AMS ensures consistent copolymer composition, molecular weight distribution, and Tg performance across production campaigns.
UPR - Non-HAP Styrene Substitute for FRP Manufacturing
Styrene's status as a US EPA Hazardous Air Pollutant (HAP) means US FRP manufacturers are subject to MACT standards under the Clean Air Act NESHAP for the polymer manufacturing sector. AMS is the most technically compatible non-HAP partial substitute for styrene in UPR systems: its vinyl aromatic structure participates in the same free-radical copolymerisation with UPR maleate/fumarate unsaturation as styrene, its lower volatility (bp 165°C vs styrene's 145°C, vapour pressure approximately one-third of styrene at 25°C) reduces evaporative HAP emissions at the work surface, and its copolymer Tg contribution is higher than styrene - AMS-crosslinked UPR has measurably higher heat distortion temperature than the styrene-crosslinked equivalent.
Partial replacement of styrene by AMS (typically 10–30% substitution level) allows UPR manufacturers to reduce their facility's total styrene HAP emission inventory while improving the composite's thermal performance. The EPA CompTox confirmation of AMS's non-HAP status is the regulatory foundation for this substitution strategy.
AMS vs. Styrene vs. Vinyltoluene - Vinyl Aromatic Monomer Comparison
Data from NCBI PubChem and ECHA. AMS's non-HAP status and higher Tg contribution are its primary competitive differentiation over styrene.
| Property | Styrene (100-42-5) | AMS (98-83-9) ✓ | Vinyltoluene (25013-15-4) |
|---|---|---|---|
| Structure | CH₂=CH–C₆H₅ | CH₂=C(CH₃)–C₆H₅ | CH₂=CH–C₆H₄–CH₃ |
| Boiling Point | 145°C | 165.3°C | 168–172°C |
| Flash Point | 31°C | 45°C | ~52–54°C |
| Ceiling Temperature | >300°C (homopolymerises readily) | ~61°C (controlled copolymerisation) | No ceiling temp. |
| Copolymer Tg Effect | Baseline: ~100°C | Higher: ~115–145°C ✓ | Similar to styrene |
| EU Carc. Class. | Carc. 1B (H350) ⚠ | Carc. 2 (H351) | Carc. 2 (H351) |
| US HAP Status | HAP-listed ⚠ | Not listed ✓ | Not listed ✓ |
| REACH Annex XIV | Not listed | Not listed ✓ | Not listed ✓ |
| Key Strength | Widest use, lowest cost | Non-HAP + Higher Tg ✓ | Higher flash point |
Storage, Inhibitor Management & Safety
AMS requires specific inhibitor management practices that differ fundamentally from solvent product handling. The TBC inhibitor system and AMS's self-polymerisation potential demand attention throughout the supply chain. Full OEL data by jurisdiction from GESTIS (IFA) and the NIOSH Pocket Guide.
📦 Storage Requirements
• Temperature: 0–25°C strictly - above 30°C accelerates self-polymerisation; below 0°C risks freezing (mp ~−23°C)
• Seal integrity: keep drums completely sealed - TBC requires dissolved oxygen, but excessive O₂ exposure accelerates peroxide formation
• Light exclusion: store in dark or opaque containers - UV light accelerates radical initiation independently of temperature
• Segregate from all radical initiators (peroxides, azo compounds), strong acids, bases, and oxidising agents
• Shelf life: 6–12 months at 0–25°C; retest TBC content before use if stored near upper limit
⚗️ Inhibitor Removal Before Polymerisation
Standard procedure: alkaline wash with 5–10% aqueous NaOH (3 portions), separate organic layer, wash with deionised water until neutral, dry over anhydrous Na₂SO₄ or molecular sieves.
• Do NOT remove inhibitor until immediately before use
• Keep inhibitor-free AMS below 10°C under nitrogen blanket if not used immediately
• Never heat inhibitor-free AMS above ambient without controlled reactor conditions with temperature monitoring
• Polymerisation of AMS without controlled heat removal is a significant exothermic runaway risk
🧤 PPE & Exposure Controls
• Chemical-resistant gloves (nitrile ≥0.15 mm), safety goggles, protective clothing for all handling
• Local exhaust ventilation - NIOSH Ceiling REL: 50 ppm; OSHA PEL: 100 ppm TWA / 200 ppm ceiling
• No ignition sources - flash point 45°C; Class 3 flammable liquid, explosion-proof electrics required
• Spill: eliminate ignition sources; absorb with dry sand or vermiculite; dispose as flammable monomer waste
Frequently Asked Questions (FAQ)
What is AMS's ceiling temperature and why does it matter for polymerisation?
The ceiling temperature (Tc) of a monomer is the temperature above which the equilibrium favours depolymerisation over chain propagation - high-MW homopolymer cannot accumulate. For AMS, Tc is approximately 61°C. Attempting to free-radical polymerise AMS homopolymer at 70–80°C yields only low-MW oligomers (dimers, trimers). However, when AMS is copolymerised with acrylonitrile, MMA, or other vinyl monomers at 60–80°C, cross-propagation thermodynamics differ from homopolymerisation - cross-propagation does not face the same ceiling temperature constraint, allowing efficient incorporation of AMS units into copolymer chains. This is why AMSAN copolymers are commercially produced at standard emulsion polymerisation temperatures, while AMS homopolymer production requires temperatures below 50°C and extended reaction times.
How does AMS compare to styrene as a reactive diluent in UPR - do I need a full reformulation?
AMS can be substituted for styrene in UPR formulations as a partial replacement (typically 10–30% by weight) without requiring full reformulation - the cure chemistry is identical. Practical adjustments needed for partial AMS substitution: (1) slightly higher viscosity of the AMS/UPR mix, possibly requiring a slight reduction in resin content; (2) slightly slower cure rate, possibly requiring adjustment of initiator type and level; (3) higher HDT of the cured laminate - generally desirable but should be verified against the application's mechanical testing protocol. For full styrene replacement, a systematic reformulation evaluation is required. Contact Sinolook for a comparative UPR reformulation technical data package.
Is the AMS dimer a problem in polymerisation?
The AMS dimer (2,4-diphenyl-4-methyl-1-pentene) is formed when AMS is stored at elevated temperatures, exposed to UV light, or when inhibitor-free AMS is held at room temperature for extended periods. The dimer does not polymerise and acts as a chain transfer agent in free-radical polymerisation, reducing molecular weight of copolymers from AMS batches with elevated dimer content. Sinolook's AMS specification of ≥99.5% purity controls total AMS content, limiting the dimer + other impurity level to ≤0.5%. For polymerisation applications sensitive to MW control (ABS rubber grafting, controlled MW SAN synthesis), an enhanced GC assay explicitly quantifying AMS dimer content is available on request - contact our technical team.
Does AMS need to be stored under nitrogen?
Standard commercial AMS storage does not require nitrogen blanketing - the TBC inhibitor functions effectively in oxygen-containing headspace. Nitrogen blanketing of inhibited AMS is counterproductive because it removes the oxygen that TBC requires as a radical scavenger. For inhibitor-free AMS held temporarily before polymerisation use, nitrogen blanketing is appropriate and recommended to prevent adventitious oxygen-initiated peroxide formation. For long-term storage of inhibited AMS in drums: maintain original sealed drums with TBC in place, at 0–25°C in a dark, ventilated flammable-liquid storage area - no nitrogen purging required.
Authoritative Technical & Regulatory References
The following references provide authoritative public data for α-Methylstyrene - for regulatory compliance verification, safety assessment, and technical application support.
| Reference Source | Description | Link |
|---|---|---|
| ECHA - AMS Substance Information | Authoritative source for current EU CLP classification (Carc. 2 H351), REACH registration, and SVHC/restriction status for CAS 98-83-9. | View → |
| PubChem - CID 7955 | NCBI PubChem record for AMS with IUPAC name, molecular structure, full physicochemical data, and GHS classifications. | View → |
| EPA CompTox - AMS | US EPA CompTox for CAS 98-83-9 confirming non-HAP status, TSCA inventory listing, and environmental/physicochemical data. | View → |
| NIOSH Pocket Guide - AMS | US NIOSH exposure limit (REL 50 ppm ceiling), IDLH value, respiratory irritant notation, and engineering control guidance. | View → |
| GESTIS - AMS Occupational Safety | IFA GESTIS substance database for CAS 98-83-9 with occupational exposure limits, physicochemical data, and health hazard information. | View → |
| ECHA - Styrene (for comparison) | ECHA substance page for styrene (CAS 100-42-5) with Carc. 1B (H350) - demonstrates AMS's more favourable carcinogen classification vs its structural analogue. | View → |
Note: External links are for reference only. Sinolook Chemical does not control third-party content. Verify current EU CLP classification via ECHA before use in EU-market products. Customers are responsible for compliance with all applicable regulations in their jurisdiction.
Buy Alpha-Methylstyrene from China - B2B Procurement Guide
As a direct AMS supplier in China, Sinolook accesses monomer production from phenol manufacturing co-product streams, providing competitive alpha methylstyrene price with volume tiers for resin producers and coating manufacturers. Full DG export documentation (Class 3 Flammable Liquid, PG III) with regular sailings from major Chinese ports.
MOQ
1 MT standard · Volume tiers: 1 MT → 5 MT → 20 MT → 100 MT
Samples
0.5–5 KG qualification samples at nominal charge, credited against first order
Lead Time
7–14 business days standard; expedited available
Packaging
180 KG iron drums / IBC tanks (900 KG) for volume orders
Contact Sinolook - Your Trusted α-Methylstyrene Supplier
Whether you are an ABS/SAN resin producer incorporating alpha-methylstyrene for heat-resistant automotive and appliance grade polymers, a US UPR manufacturer substituting AMS for styrene to reduce HAP emission inventory, an acrylic coating resin producer, a hydrocarbon tackifier manufacturer, or a specialty chemical company requiring AMS as a fragrance or pharmaceutical intermediate - Sinolook Chemical delivers purity ≥99.5% monomer quality, consistent inhibitor control, full regulatory documentation (non-HAP declaration, EU CLP-compliant SDS, TSCA confirmation), and competitive supply from an experienced AMS manufacturer in China. Contact us today - our team responds within 24 hours.
📱 Phone / WeChat
0086 134-0071-5622🌐 Website
www.sinolookchem.comSinolook Chemical Co., Ltd. - Global Supplier of Organic Monomers, Specialty Solvents & Industrial Chemicals
Hot Tags: alpha-methylstyrene, China alpha-methylstyrene manufacturers, suppliers
