Isoprene CAS 78-79-5
Chelora Chemicals supplies inhibitor-stabilised isoprene to synthetic polyisoprene, butyl rubber and SIS block copolymer producers worldwide. Because isoprene peroxidises and dimerises on storage, every consignment leaves with a batch-specific COA including inhibitor, peroxide and dimer data, the current SDS and full dangerous-goods documentation.
Also known as: 2-Methyl-1,3-butadiene · Isopentadiene · 2-Methylbutadiene · IP
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Price, lead time and a sample COA for Isoprene, usually within one working day. We ship worldwide.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (GC purity, inhibitor, peroxide, dimer)
- Safety Data Sheet (SDS)
- Transport and dangerous-goods documents
- Third-party inspection on request
- Certificate of origin
What is Isoprene?
Isoprene is a five-carbon conjugated diene, formula C₅H₈, and the monomer unit of natural rubber. At room temperature it is a colourless, very volatile and highly flammable liquid with a mild petroleum odour, boiling at about 34 °C.
It is the only monomer that gives a synthetic rubber chemically equivalent to natural rubber. High-cis polyisoprene made with Ziegler-Natta or lithium catalysts matches natural rubber in tack, green strength and heat build-up, which is why tyre and medical goods makers buy it.
Isoprene is supplied as a stabilised liquid, normally 99% or better, with 4-tert-butylcatechol (TBC) added to suppress peroxide formation and premature polymerisation. The inhibitor is part of the product, not an impurity.
Commercially, most isoprene is a by-product of the C5 fraction from naphtha steam cracking, so availability moves with cracker feed slate, exactly as it does for butadiene.
Why Isoprene specifically
- A conjugated diene. The methyl-substituted diene structure allows stereospecific 1,4-polymerisation to high-cis rubber.
- Synthetic natural rubber. Polyisoprene is the only drop-in synthetic equivalent to natural rubber in demanding tyre and medical applications.
- The butyl rubber comonomer. A small percentage of isoprene in isobutylene gives butyl rubber its cure sites.
- Block copolymer feedstock. SIS and SI block copolymers for hot-melt adhesives are built on isoprene blocks.
How Isoprene is Manufactured
Isoprene is mostly recovered from the C5 stream of naphtha and gas-oil steam crackers. On-purpose routes exist but are used only where cracker C5 is short.
- Steam cracking of naphtha or gas oil. The pyrolysis gasoline C5 cut contains roughly 15 to 20% isoprene alongside pentenes, pentanes, cyclopentadiene and piperylene.
- Cyclopentadiene removal. The C5 cut is heat-soaked so cyclopentadiene dimerises to dicyclopentadiene, which is then separated by distillation.
- Extractive distillation. Isoprene is separated from the remaining C5 olefins and paraffins with a polar solvent such as acetonitrile, DMF or NMP.
- Finishing columns. Solvent, acetylenes, carbonyls and alpha-acetylene are stripped to reach polymerisation grade at 99% or better.
- On-purpose routes. Propylene dimerisation, isobutylene-formaldehyde condensation and isoamylene dehydrogenation are used where by-product supply is insufficient.
- Inhibition and cold storage. TBC is dosed immediately and the product is stored cool under nitrogen, because isoprene dimerises to dipentene on warming.
Typical Commercial Specification
Figures below are representative of commercial polymerisation-grade isoprene. Tell us your catalyst system and we will advise on the grade and the inhibitor level you should specify.
| Parameter | Typical Value |
|---|---|
| Appearance | Clear colourless liquid, free of suspended matter |
| Isoprene content | 99.0% min by weight (99.5% for solution grades) |
| Inhibitor (TBC) | 50 – 150 ppm, to customer requirement |
| Cyclopentadiene | 1 ppm max |
| Total acetylenes | To grade, typically 5 ppm max |
| Carbonyls (as acetaldehyde) | To grade, typically 5 ppm max |
| Dimers | To grade, typically 500 ppm max |
| Peroxides (as H₂O₂) | To grade, typically 5 ppm max |
| Water | To grade, typically 50 ppm max for solution grades |
| Non-volatile residue | To grade, typically 50 ppm max |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | C₅H₈ (CH₂=C(CH₃)–CH=CH₂) |
| Molecular weight | 68.12 g/mol |
| Appearance | Colourless volatile liquid |
| Boiling point | About 34 °C |
| Melting point | About −146 °C |
| Flash point | About −54 °C (closed cup) |
| Density | About 0.681 g/cm³ at 20 °C |
| Vapour pressure | About 61 kPa at 20 °C |
| Vapour density (relative to air) | About 2.4, heavier than air |
| Flammable limits in air | About 1.5 to 8.9% by volume |
| Autoignition temperature | About 395 °C |
| Solubility in water | Very low (about 0.6 g/L at 25 °C) |
| Incompatibilities | Oxygen, peroxides, strong oxidisers, acids; polymerises exothermically |
Behaviour in the process
Isoprene is more reactive than most C5 hydrocarbons and this governs how it is stored and fed to polymerisation:
- Peroxide formation. Oxygen exposure produces peroxides that can initiate runaway polymerisation. Nitrogen blanketing is mandatory.
- Dimerisation. On warm storage isoprene forms dipentene and other dimers, which lower monomer purity and foul equipment.
- Catalyst sensitivity. Cyclopentadiene, acetylenes, carbonyls and water deactivate anionic and Ziegler-Natta catalysts at ppm level.
- High volatility. At 61 kPa vapour pressure the vapour escapes readily and pools at low points, so closed transfer is standard.
Isoprene Grades and Related Monomers
Isoprene is bought by grade, and the grade is defined by what the catalyst will tolerate rather than by the headline purity figure.
| Material | Origin / type | When it is the right choice |
|---|---|---|
| Polymerisation grade isoprene | 99.0%+ TBC-stabilised | Emulsion and high-cis solution polyisoprene |
| Solution (anionic) grade isoprene | 99.5%+, very low carbonyls and water | SIS and SI block copolymers, lithium-catalysed rubber |
| Chemical grade isoprene | 95 to 98% | Terpene chemistry, specialty intermediates, non-critical uses |
| 1,3-Butadiene | C4 diene, CAS 106-99-0 | SBR, polybutadiene and ABS where natural rubber properties are not required |
| Piperylene (1,3-pentadiene) | C5 diene co-product | Hydrocarbon resins, not a rubber monomer substitute |
Stated plainly: for synthetic natural rubber there is no substitute for isoprene. Butadiene makes a different rubber with different properties, and the choice between them is a formulation decision rather than a swap.
Industries We Supply Isoprene To
The same stabilised liquid goes to a polyisoprene plant, a butyl rubber line and an adhesives producer. What changes is the grade, the carbonyl limit and the inhibitor level each requires.
Where Isoprene is Used
Isoprene is bought overwhelmingly as a rubber monomer, with adhesives and specialty chemistry behind it.
In polyisoprene manufacture
Isoprene is polymerised in solution with a Ziegler-Natta titanium system or an organolithium initiator. The titanium route gives 96 to 98% cis-1,4 content and natural-rubber-like behaviour; the lithium route gives about 92% cis with cleaner polymer. Carbonyl and cyclopentadiene limits decide catalyst consumption on both routes.
In butyl rubber manufacture
Isoprene is copolymerised with isobutylene at about −95 °C in methyl chloride with an aluminium chloride catalyst. Only a few percent of isoprene is used, but its purity controls the unsaturation and therefore the cure behaviour of the finished butyl rubber.
Need a specific grade, purity and packing format?
Tell us the grade, your catalyst system and the carbonyl limit it needs, the packing format you can receive and the annual quantity. We will come back with a price, a lead time, a sample COA and the full documentation set.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis, with inhibitor and peroxide figures reported alongside purity because they are safety-critical for this product.
- Isoprene content — by gas chromatography, the primary grade measure.
- TBC inhibitor level — by colorimetry or HPLC, confirming the stability margin.
- Cyclopentadiene — reported in ppm because it is the most damaging catalyst poison.
- Carbonyls and acetylenes — measured for anionic and Ziegler-Natta grades.
- Peroxides — tested because they initiate uncontrolled polymerisation.
- Dimer content — an indicator of storage age and temperature history.
- Water and non-volatile residue — measured to limits relevant to catalyst performance.
Common Process Problems & Likely Causes
When isoprene causes trouble, it is usually carbonyls, cyclopentadiene, peroxides or warm storage. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Catalyst consumption rises | Carbonyls, cyclopentadiene or water in the feed | COA impurity profile and drier performance |
| Cis content below target | Cyclopentadiene or acetylenes affecting active sites | Cyclopentadiene figure and catalyst ratio |
| Gel or popcorn polymer in tanks | Peroxides, low inhibitor or warm storage | TBC level, nitrogen blanket, tank temperature |
| Dimer content rising on storage | Long hold time or elevated temperature | Lot age and storage temperature history |
| Molecular weight drifting in anionic polymerisation | Protic impurities killing the lithium initiator | Water and carbonyl figures on the COA |
| Odour or colour in the delivered monomer | Oxidation products or dimer | Peroxide and non-volatile residue results |
| Pressure build-up in storage tank | Warm storage and high vapour pressure | Tank temperature and vapour space composition |
Packaging, Storage & Shipping
- Standard packing. ISO tank containers and road tankers; drums for small chemical-grade quantities, with the inhibitor level declared on the label.
- Oxygen exclusion. Nitrogen blanketing is essential. Oxygen drives peroxide formation and gel.
- Temperature control. Cool storage, ideally below 20 °C, limits dimerisation and inhibitor consumption.
- Storage. Well-ventilated, shaded, earthed and bunded areas with gas detection, away from ignition sources.
- Material compatibility. Carbon steel and stainless steel are standard. Avoid copper alloys and uninhibited contact with oxidisers.
- Segregation. Keep apart from oxidisers, peroxides and acids.
- Shelf life. Limited by inhibitor consumption and dimerisation, typically three to six months in cold, oxygen-free storage.
- Transport classification. UN 1218, isoprene stabilised, Class 3 flammable liquid, packing group I.
Hazards & Safe Handling
Isoprene is a highly flammable, very volatile liquid and a suspected carcinogen. Fire and peroxide formation are the physical hazards; vapour exposure control is the central health issue.
- Flammability. Flash point about −54 °C and a wide flammable range. Control ignition sources, earth and bond all transfer equipment.
- Health classification. Classified as a suspected carcinogen (Category 2) in the EU and listed as reasonably anticipated to be a human carcinogen in the US. Keep exposure as low as reasonably practicable.
- Peroxides and runaway polymerisation. Exclude oxygen, maintain inhibitor and inspect tanks regularly.
- Heavy vapour. Vapour pools at low points. Ventilate and monitor at low level.
- Exposure routes. Inhalation is the main route; the liquid also defats and irritates skin.
- PPE. Flame-resistant clothing, chemical-resistant gloves, eye protection and respiratory protection for breaches of containment.
- Environment. Volatile and not significantly bioaccumulative, but prevent entry to drains and watercourses.
Regulatory & Compliance Notes
Isoprene is a regulated flammable liquid with health classifications that vary by territory. The notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser.
- GHS classification. Flammable liquid Category 1, carcinogenicity Category 2, and aspiration hazard. The SDS carries the full hazard statements.
- REACH and inventories. Registered under EU REACH and listed on the major chemical inventories.
- Dangerous goods transport. UN 1218, Class 3, PG I, stabilised. ADR, IMDG, IATA and DOT rules apply to tank design, labelling and routing.
- Occupational exposure. Exposure limits and monitoring requirements differ by jurisdiction; many apply a low TWA because of the carcinogenicity classification.
- Process safety. Bulk storage usually falls under major-hazard and hazardous-area classification rules.
- Quality agreements. Rubber producers commonly require documented carbonyl, cyclopentadiene and inhibitor limits with change control.
We Supply Isoprene Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Isoprene from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork and freight so the material arrives ready to use.
- Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
- Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where routing and cargo rules allow.
- Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
- Flexible volumes. From a single ISO tank up to repeat bulk shipments on a supply contract.
- Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.
Buying Isoprene from Chelora
We are an independent sourcing and supply partner. For isoprene that means settling three things at enquiry: the grade your catalyst needs, the inhibitor level and whether it must be removed before use, and the cold, oxygen-free handling route to your site.
- Documentation on every lot. Batch-specific COA (GC purity, inhibitor, peroxide, dimer), plus SDS and the full transport paperwork.
- Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
- Quantities. From a single ISO tank through to full bulk shipments on contract supply.
- Grade matching. Polymerisation, solution or chemical grade matched to your catalyst system, with advice on inhibitor removal before polymerisation.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Related products. 1,3-Butadiene, Isobutylene, Styrene Monomer and other feedstocks alongside Isoprene from one supplier.
How ordering works
- Send the enquiry. Product, grade or purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
- We quote. Price, lead time, packing format and a sample COA, normally within one working day.
- Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
- Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
- Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
- Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.
Isoprene — Common Questions
The questions our technical desk is asked most often about Isoprene. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of isoprene?
The CAS number for isoprene is 78-79-5, and its EC number is 201-143-3. Its molecular formula is C₅H₈ with a molecular weight of 68.12 g/mol, and it is classified under HS code 2901.24.
What is isoprene used for?
Mainly for synthetic polyisoprene rubber, the closest synthetic equivalent to natural rubber. It is also the comonomer in butyl rubber, the mid-block in SIS adhesive copolymers, and a feedstock for hydrocarbon resins and fine chemicals.
Do you supply isoprene worldwide?
Yes. Chelora Chemicals supplies and exports isoprene worldwide — across Asia Pacific, Europe, the Middle East, Africa and the Americas, as well as throughout India. Every consignment carries the COA with inhibitor and peroxide data, the SDS and the dangerous-goods documentation.
Why is isoprene stabilised with TBC?
Without an inhibitor, isoprene forms peroxides and gel on storage. 4-tert-butylcatechol at about 50 to 150 ppm scavenges the radicals that start those reactions, so it is a safety additive as well as a quality one.
How is isoprene manufactured?
Mostly by extractive distillation of the C5 cut from naphtha steam cracking, after cyclopentadiene has been removed by dimerisation. On-purpose routes include isoamylene dehydrogenation and the isobutylene-formaldehyde process.
What is the difference between polymerisation grade and solution grade?
Both are above 99% isoprene, but solution grade carries much tighter limits on carbonyls, water and cyclopentadiene because anionic lithium catalysts are destroyed by protic and carbonyl impurities at ppm level.
Is isoprene hazardous?
Yes. It is a highly flammable liquid with a flash point near −54 °C and is classified as a suspected carcinogen. It also forms peroxides. Closed handling, oxygen exclusion, inhibitor maintenance and ignition control are the key safeguards.
What are the UN number and transport class?
UN 1218, isoprene stabilised, Class 3 flammable liquid, packing group I. ADR, IMDG, IATA and DOT rules apply to the tank, labelling and routing.
How should isoprene be stored?
Cool, shaded, earthed tanks under a nitrogen blanket with oxygen excluded, ideally below 20 °C, away from heat and oxidisers. Check inhibitor, peroxide and dimer levels during storage.
What packing sizes and order quantities are available?
ISO tank containers and road tankers for bulk, with drums available for smaller chemical-grade quantities. Orders run from a single ISO tank up to repeat bulk loads on contract supply.
What is the typical shelf life?
Limited by inhibitor consumption and dimerisation, typically three to six months in cold, oxygen-free storage. Re-test TBC, peroxides and dimer rather than assume.
Can isoprene replace natural rubber completely?
In many applications yes — polyisoprene matches natural rubber closely in cis content and properties, and is preferred where protein allergens are unacceptable. In some heavy-duty tyre components natural rubber still has an advantage in green strength and tear resistance.
Ready to source Isoprene?
Send us your specification, grade and annual volume. You will get a price, a realistic lead time and a sample COA from someone who understands what the material has to do in your process — delivered anywhere in the world.