Styrene Monomer
A monomer that wants to polymerise on its own. Inhibited with TBC and shipped cold, because the reaction it is bought for will start in the tank if you let it.
Molecular Structure
What is Styrene Monomer?
Styrene is a benzene ring carrying a vinyl group — a two-carbon chain with a carbon–carbon double bond. It is a clear liquid with a sharp, sweet odour, boiling at 145.2 °C.
That vinyl group is conjugated with the aromatic ring, which stabilises the radical formed when the double bond opens. This is precisely why styrene polymerises so readily, and it is also why styrene is a demanding product to store: the same reaction that makes polystyrene will proceed slowly in a storage tank, accelerating as it goes because polymerisation is exothermic.
Commercial styrene is therefore always shipped inhibited, normally with 10–15 ppm of tert-butylcatechol. TBC needs dissolved oxygen to work, so — unlike most flammable liquids — styrene tanks are not fully nitrogen-blanketed. Temperature control below 25 °C and regular TBC and polymer testing are part of normal custody.
Chelora supplies styrene monomer at ≥99.7 wt% with TBC at 10–15 ppm, polymer content below 10 ppm, and full inhibitor and temperature history on the Certificate of Analysis. Shipped UN 2055, stabilised, with age and storage-life guidance for the consignment.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
Everything about styrene follows from one bond. The vinyl C=C is conjugated with the ring, which makes it unusually easy to open — the basis of the entire polystyrene industry, and the reason the monomer needs an inhibitor to sit still.
Skeletal structure — vinyl group (shown in gold) at C-1
Structural Identity
- IUPAC NameEthenylbenzene
- Common namesVinylbenzene, phenylethene
- Molecular FormulaC₈H₈
- Molecular Weight104.15 g/mol
- Hybridisationsp² throughout (ring and vinyl)
- Bond typeAromatic ring conjugated with C=C
- Bond lengths1.39 Å ring C–C; 1.33 Å vinyl C=C
- Key reactionFree-radical chain polymerisation
- InhibitorTBC, 10–15 ppm, requires dissolved O₂
- CAS Number100-42-5
- InChI KeyPPBRXRYQALVLMV-UHFFFAOYSA-N
Product Specifications
Chelora supplies Styrene Monomer in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | Styrene monomer, stabilized |
|---|---|
| CAS Number | 100-42-5 |
| Molecular formula | C₈H₈ |
| Molecular weight | 104.15 g/mol |
| Purity (min) | ≥ 99.70 wt% (typically ≥ 99.85) |
| TBC inhibitor | 10 – 15 ppm wt |
| Polymer content (max) | ≤ 10 ppm wt |
| Aldehydes as benzaldehyde (max) | ≤ 100 ppm wt |
| Peroxides as H₂O₂ (max) | ≤ 100 ppm wt |
| Ethylbenzene (max) | ≤ 0.10 wt% |
| Total xylenes (max) | ≤ 0.05 wt% |
| Sulfur (max) | ≤ 1.0 ppm wt |
| Chlorides (max) | ≤ 1.0 ppm wt |
| Water (max) | ≤ 200 ppm wt |
| Colour | ≤ 10 Pt-Co (Hazen) |
| Density | 0.905 – 0.907 g/cm³ at 20 °C |
| Flash point | 31 °C (closed cup) |
| Autoignition temperature | 490 °C |
| Flammable limits | 0.9 – 6.8% v/v in air |
| Storage temperature | Below 25 °C; below 20 °C preferred |
| UN Number | UN 2055 (Styrene monomer, stabilized) |
| IMDG / ADR Class | Class 3 (Flammable Liquid), PG III |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of Styrene Monomer.
Polystyrene & EPS
Bulk or suspension polymerisation gives general-purpose and high-impact polystyrene for packaging, appliances and housewares, and expandable beads for insulation board and protective packaging.
ABS & SAN
Copolymerised with acrylonitrile and butadiene to give ABS for automotive trim, appliance housings and electronics, and with acrylonitrile alone for transparent, rigid SAN.
SBR & Styrene-Butadiene Latex
Emulsion and solution copolymerisation with butadiene gives SBR for tyres and technical rubber goods, and SB latex for paper coating, carpet backing and adhesives.
SBS & SIS Block Copolymers
Anionic sequential polymerisation gives thermoplastic elastomers for bitumen modification, footwear soling, and the pressure-sensitive and hot-melt adhesive market.
Unsaturated Polyester Resins
Styrene acts as both reactive diluent and cross-linking monomer in UPR, curing into the polyester backbone for FRP boats, tanks, pipe, gelcoats and construction composites.
Styrene-Acrylic Dispersions
Copolymerised with acrylic esters into waterborne binders for architectural paints, construction chemicals, textile finishing and paper coating.
Why source Styrene Monomer through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market supply.
Grade Flexibility
Supplied to standard monomer specification with TBC, polymer, aldehyde and peroxide levels certified, and inhibitor and temperature history recorded for the consignment.
Full Documentation
CoA, SDS, UN transport docs, REACH compliance, and destination-market certificates with every shipment.
Logistics Support
Experienced in inhibited monomer logistics — temperature-controlled and insulated tanks, inhibitor verification on receipt, and transit-time planning against remaining storage life.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Keep bulk storage below 25 °C, and below 20 °C where possible — polymerisation rate roughly doubles for every 10 °C rise.
- Do not fully inert with nitrogen. TBC needs dissolved oxygen to function, so maintain the oxygen level specified in the SDS rather than blanketing to zero.
- Verify TBC content on receipt and at regular intervals during storage; re-inhibit or use the material before the inhibitor is depleted.
- Monitor tank temperature continuously with high-temperature alarms — a rising temperature with no external heat source is the first sign of runaway polymerisation.
- Test for polymer content periodically; increasing polymer or a rise in viscosity means the material is reacting and must be assessed immediately.
- Operate stock on a strict first-in, first-out basis and track remaining storage life against the certificate date, not the delivery date.
- Bond and earth all tanks, tankers and hoses before transfer, and use ATEX/IECEx-rated equipment throughout.
- Keep away from peroxides, strong acids, oxidisers, aluminium chloride and other polymerisation catalysts, and protect tanks from direct sunlight.
Hazard Summary
Classification: Flam. Liq. 3 (H226) · Repr. 2 (H361d) · STOT RE 1 (H372, hearing organs) · Acute Tox. 4 inhalation (H332) · STOT SE 3 (H335) · Skin and Eye Irrit. 2.
Runaway polymerisation: This is the defining hazard. Styrene self-polymerises exothermically, and the heat released accelerates the reaction further. Once inhibitor is exhausted or the temperature climbs, a sealed tank can over-pressure and rupture. Temperature monitoring and inhibitor verification are not optional.
Inhibitor and oxygen: TBC only works in the presence of dissolved oxygen. Fully nitrogen-blanketing a styrene tank defeats the inhibitor — follow the supplier's oxygen specification rather than standard flammable-liquid practice.
Health: IARC reclassified styrene as Group 2A, probably carcinogenic to humans, in 2019. It is also classified for hearing damage on repeated exposure and as a suspected reproductive toxicant.
Exposure limits: ACGIH TLV 10 ppm 8-h TWA with a 20 ppm STEL; the EU binding limit is 50 mg/m³ (≈12 ppm) TWA with a 100 mg/m³ STEL; OSHA PEL 100 ppm TWA. Confirm the limit in force in your jurisdiction.
PPE minimum: Chemical splash goggles, nitrile or Viton gloves, flame-retardant antistatic clothing, and organic-vapour respiratory protection where ventilation cannot hold exposure below the limit.
Consult the full SDS for exposure limits, spill containment, emergency response, and disposal before any use.
Frequently Asked Questions
Technical and commercial questions about Styrene Monomer sourcing and specifications.
What is styrene monomer used for?
Styrene is a polymer building block. The largest outlets are polystyrene and EPS, ABS and SAN engineering plastics, styrene-butadiene rubber and latex, SBS and SIS thermoplastic elastomers, unsaturated polyester resins for composites, and styrene-acrylic dispersions for waterborne paints and construction chemicals.
Why does styrene need an inhibitor?
Styrene's vinyl group is conjugated with the aromatic ring, which stabilises the radical formed when the double bond opens and makes spontaneous free-radical polymerisation easy. Left alone, styrene slowly polymerises at ambient temperature, and because the reaction is exothermic it accelerates itself. TBC — tert-butylcatechol — at 10–15 ppm scavenges those radicals and holds the reaction off for the expected storage life.
Why shouldn't styrene tanks be nitrogen-blanketed?
Because TBC needs dissolved oxygen to function. The inhibitor works by forming peroxy radicals, which requires oxygen to be present, so removing all oxygen from the headspace actually disables the protection you are relying on. This is the opposite of normal practice for flammable liquids, and it catches people out. Follow the oxygen concentration specified in the SDS, and never inert a styrene tank to zero oxygen.
How long can styrene be stored?
It depends on temperature and inhibitor level rather than a fixed shelf life. Storage life shortens sharply as temperature rises — as a rule of thumb the polymerisation rate roughly doubles for every 10 °C. Below 20 °C with full TBC, several months is normal; at 30 °C or above it falls off quickly. Track TBC content and polymer content by test rather than assuming, and run stock first-in, first-out.
What are the warning signs of runaway polymerisation?
A rising tank temperature with no external heat source is the primary signal, usually alongside an increase in viscosity, cloudiness or visible polymer, and declining TBC on test. Treat any unexplained temperature rise as an emergency: it is self-accelerating, and cooling and inhibitor addition are far more effective early. Your site emergency plan should cover this specifically, and the SDS gives the detail.
What documentation does Chelora provide?
Every shipment includes a Certificate of Analysis covering purity, TBC inhibitor level, polymer content, aldehydes, peroxides, ethylbenzene, sulfur, chlorides, water and colour; a Safety Data Sheet (GHS/REACH); UN 2055 Class 3 PG III transport documentation declared as stabilized; inhibitor and temperature history for the consignment; an origin certificate; and any destination-market certificates required.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Styrene Monomer grade, volume, logistics, documentation, and lead times. We respond within one business day.
