Butyl Rubber CAS 9010-85-9
Chelora Chemicals supplies regular, chlorinated and brominated butyl rubber to tyre, pharmaceutical closure and technical rubber producers worldwide. Every consignment leaves with a batch-specific COA covering Mooney viscosity, unsaturation, halogen content and ash, the current SDS and full export documentation.
Also known as: IIR · Butyl rubber · Isobutylene-isoprene rubber · CIIR / BIIR · Halobutyl
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Price, lead time and a sample COA for Butyl Rubber, usually within one working day. We ship worldwide.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (Mooney viscosity, unsaturation, halogen content)
- Safety Data Sheet (SDS)
- Transport and export documents
- Third-party inspection on request
- Certificate of origin
What is Butyl Rubber?
Butyl rubber is a copolymer of isobutylene with 1 to 2.5 mol% isoprene, the isoprene providing just enough unsaturation for sulphur vulcanisation.
That very low unsaturation is the point: the almost fully saturated chain gives exceptional gas impermeability and excellent resistance to ozone, ageing and chemicals.
Halogenated versions — chlorobutyl and bromobutyl — were developed to allow co-vulcanisation with diene rubbers, which regular butyl cannot do. Halobutyl now accounts for most of the volume, principally in tyre innerliners.
Beyond tyres, butyl is the standard material for pharmaceutical stoppers and seals, where its impermeability and chemical inertness matter more than its cost.
Why butyl rubber specifically
- Exceptional gas impermeability. Roughly ten times less permeable to air than natural rubber, which is why tyres hold pressure.
- Very low unsaturation. Only 1 to 2.5 mol% isoprene, giving outstanding ozone and ageing resistance.
- High damping. Excellent vibration and shock absorption, used in engine mounts and damping applications.
- Chemical and moisture resistance. The property that makes it the standard for pharmaceutical closures.
How Butyl Rubber is Manufactured
Butyl rubber is made by cationic copolymerisation of isobutylene and isoprene at very low temperature, then halogenated if required.
- Monomer feed. High-purity isobutylene with 1 to 2.5 mol% isoprene, both rigorously dried.
- Cationic polymerisation. Carried out at about −95 °C in methyl chloride with an aluminium chloride catalyst.
- Slurry handling. The polymer forms as a slurry in the diluent and is flashed off with steam and hot water.
- Halogenation. Regular butyl is dissolved in hexane and reacted with chlorine or bromine to give CIIR or BIIR.
- Stabilisation. Halobutyl is stabilised with calcium stearate and antioxidant to prevent dehydrohalogenation.
- Finishing and baling. The crumb is dried, baled and wrapped in polyethylene film.
Typical Commercial Specification
Figures below are representative of a bromobutyl innerliner grade. Regular and pharmaceutical grades differ — tell us the application and we will send the matching sheet.
| Parameter | Typical Value |
|---|---|
| Appearance | White to light tan bales, free of contamination |
| Mooney viscosity ML (1+8) at 125 °C | 32 – 51 depending on grade |
| Isoprene content | 1.0 – 2.5 mol% |
| Bromine content (BIIR) | Typically 1.8 – 2.1% |
| Chlorine content (CIIR) | Typically 1.1 – 1.3% |
| Volatile matter | 0.5% max |
| Ash content | 0.5% max |
| Stabiliser | Calcium stearate and antioxidant to grade |
| Extractables (pharmaceutical grades) | To pharmacopoeial requirements |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | Copolymer of isobutylene and isoprene |
| Appearance | White to light tan bales |
| Density | About 0.92 g/cm³ |
| Glass transition temperature | About −65 °C |
| Air permeability | Roughly one tenth that of natural rubber |
| Ozone and weather resistance | Excellent |
| Damping | Very high, with low resilience |
| Service temperature | About −50 to 120 °C |
| Chemical resistance | Excellent to acids, alkalis and polar fluids; poor to hydrocarbons |
| Water vapour permeability | Very low |
| Incompatibilities | Hydrocarbon oils and fuels, strong oxidisers |
Behaviour in the process
Butyl's low unsaturation creates both its advantages and its processing peculiarities:
- Cannot co-vulcanise with diene rubbers. Regular butyl cures at a different rate; halogenation was developed specifically to solve this.
- Very low resilience. High damping means energy is absorbed rather than returned, useful in mounts, unhelpful in tread.
- Slow cure. Low unsaturation means slower sulphur cure; halobutyl grades cure faster through the halogen sites.
- Dehydrohalogenation risk. Halobutyl degrades if overheated or stored warm, which is why it is stabilised and has a defined shelf life.
Butyl Types and Alternatives
Butyl rubber is bought by type, since regular and halogenated grades serve quite different purposes.
| Material | Origin / type | When it is the right choice |
|---|---|---|
| Regular butyl (IIR) | Non-halogenated | Inner tubes, curing bladders, damping and pharmaceutical closures |
| Chlorobutyl (CIIR) | 1.1 to 1.3% chlorine | Tyre innerliner and applications needing co-vulcanisation |
| Bromobutyl (BIIR) | 1.8 to 2.1% bromine | Tyre innerliner with faster cure and better adhesion — the volume grade |
| EPDM | CAS 25038-36-2 | Better heat and weather resistance; far higher gas permeability |
| Polyisobutylene | Non-vulcanisable | Sealants, adhesives and tackifiers |
Stated plainly: if the part must bond to a diene rubber carcass, it needs halobutyl. Regular butyl remains right for tubes, bladders, damping and pharmaceutical closures where co-vulcanisation is not required.
Industries We Supply Butyl Rubber To
Butyl rubber serves tyres, pharmaceuticals, construction and technical rubber markets.
Where Butyl Rubber is Used
Tyre innerliner takes the majority of butyl rubber, with pharmaceutical closures the most demanding smaller application.
In tyre innerliner
Halobutyl innerliner is what keeps a tubeless tyre inflated: its permeability is roughly a tenth that of natural rubber, so pressure loss per month falls from several percent to a fraction. Bromobutyl is preferred over chlorobutyl in most modern formulations because it cures faster and adheres better to the carcass, which matters on a high-speed building line.
In pharmaceutical closures
Butyl stoppers combine very low moisture and gas permeability with chemical inertness and low extractables, which is why they are the standard for injectable drug vials. Pharmaceutical grades are made and tested to pharmacopoeial requirements for extractables and biological reactivity, and the qualification burden is why the supplier base is so narrow.
Need a specific grade, purity and packing format?
Tell us the grade, the type, Mooney viscosity and whether pharmaceutical qualification is needed, 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 the grade's defining properties, so your compound laboratory can release against the actual material.
- Mooney viscosity — ML (1+8) at 125 °C, the primary processing indicator.
- Unsaturation — isoprene content, controlling cure behaviour.
- Halogen content — bromine or chlorine level, defining cure chemistry and adhesion.
- Volatile matter and ash — confirming drying and residue levels.
- Stabiliser content — confirming protection against dehydrohalogenation.
- Extractables — for pharmaceutical grades, to pharmacopoeial requirements.
Common Process Problems & Likely Causes
When butyl rubber causes trouble, it is usually scorch, adhesion or storage. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Innerliner adhesion to carcass poor | Halogen content low, or regular butyl used instead of halobutyl | Halogen figure and grade confirmation |
| Scorch during processing | Halogen content high or cure system too active | Halogen content, cure package and processing temperature |
| Cure rate slower than expected | Unsaturation below specification | Isoprene content and cure system design |
| Discolouration or degradation of stored bales | Dehydrohalogenation from warm storage | Warehouse temperature and stock age |
| Air retention below target | Liner gauge, compound or grade substitution | Grade, compound design and liner thickness |
| Extractables failing pharmacopoeial test | Non-pharmaceutical grade used | Grade qualification and documentation |
Packaging, Storage & Shipping
- Standard packing. 25 to 35 kg bales wrapped in polyethylene film, palletised or crated.
- Temperature control. Store below 30 °C. Halobutyl dehydrohalogenates in warm storage, which degrades cure behaviour irreversibly.
- Storage. Cool, dry, covered warehousing away from direct sunlight and heat sources.
- Stock rotation. First in, first out; halobutyl has a defined shelf life, unlike most elastomers.
- Segregation. Keep regular, chlorobutyl and bromobutyl strictly separated; substitution causes adhesion failures.
- Contamination. Keep away from oils and hydrocarbons, which butyl absorbs readily.
- Shelf life. Typically 12 months for halobutyl in cool storage; longer for regular butyl.
- Transport classification. Not classified as dangerous goods for transport.
Hazards & Safe Handling
Butyl rubber is an inert polymer with no significant health hazard in normal handling. The practical concerns are manual handling of bales, mixing fume and compound ingredients.
- Inert in normal handling. Not classified as hazardous. Bales present no chemical risk in storage or transport.
- Manual handling. Bales are a significant ergonomic hazard; use mechanical handling where possible.
- Mixing fume. Internal mixer and mill operations generate rubber process fume; ventilation and extraction are required.
- Thermal decomposition. Overheating halobutyl releases hydrogen halide; avoid excessive processing temperature and ventilate.
- Compound ingredients. Curatives, oils and fillers carry their own hazards; the compound SDS governs.
- Environment. Inert but persistent; contain waste and use established rubber recycling routes.
Regulatory & Compliance Notes
Butyl rubber is unregulated for transport, with pharmacopoeial requirements applying to closure grades. The notes below are orientation rather than legal advice.
- GHS classification. Not classified as hazardous.
- Transport. Not classified as dangerous goods. Standard packaged cargo documentation applies.
- Pharmaceutical closures. Must meet USP, EP and JP requirements for elastomeric closures, including extractables and biological reactivity testing.
- Food contact. Butyl goods for food contact require compliance documentation at compound level.
- REACH and inventories. Polymers are exempt from REACH registration, though monomers and additives are not.
- Tyre specifications. Innerliner performance is governed by tyre manufacturer specifications rather than by public standards.
We Supply Butyl Rubber Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Butyl Rubber 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 pallet of bales 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 Butyl Rubber from Chelora
We are an independent sourcing and supply partner. For butyl rubber that means settling three things at enquiry: regular, chlorobutyl or bromobutyl, the Mooney viscosity your process requires, and whether pharmacopoeial documentation is needed for closure applications.
- Documentation on every lot. Batch-specific COA (Mooney viscosity, unsaturation, halogen content), 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 pallet of bales through to full bulk shipments on contract supply.
- Grade matching. Regular, chlorinated or brominated butyl at the Mooney viscosity and halogen content your application requires.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Related products. Isobutylene, Isoprene, Ethylene Propylene Diene Rubber and other feedstocks alongside Butyl Rubber 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.
Butyl Rubber — Common Questions
The questions our technical desk is asked most often about Butyl Rubber. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of butyl rubber?
The CAS number for butyl rubber is 9010-85-9, and it is classified under HS code 4002.31. As a polymer it is exempt from REACH registration, though its monomers are not.
What is butyl rubber used for?
Mainly tyre innerliner, where its gas impermeability holds inflation pressure. It is also used for inner tubes, tyre curing bladders, pharmaceutical vial stoppers, damping mounts, tank linings and construction sealants.
Do you supply butyl rubber worldwide?
Yes. Chelora Chemicals supplies and exports butyl rubber worldwide — across Asia Pacific, Europe, the Middle East, Africa and the Americas, as well as throughout India, in 25 to 35 kg bales.
What is the difference between regular butyl and halobutyl?
Halogenation with chlorine or bromine adds reactive sites that allow the rubber to co-vulcanise with the diene rubbers in a tyre carcass. Regular butyl cannot do this, which is why halobutyl dominates innerliner applications.
Why is butyl rubber so impermeable to air?
Because the isobutylene chain packs tightly with methyl groups on alternate carbons, leaving very little free volume for gas diffusion. Permeability is roughly a tenth that of natural rubber.
How is butyl rubber manufactured?
By cationic copolymerisation of isobutylene with 1 to 2.5 mol% isoprene at about −95 °C in methyl chloride with aluminium chloride catalyst, then halogenated in hexane solution for CIIR or BIIR grades.
What is the difference between chlorobutyl and bromobutyl?
Bromobutyl cures faster and gives better adhesion to the tyre carcass, which is why it dominates modern innerliner. Chlorobutyl is slower curing and more scorch resistant, which suits some processing conditions.
Why does halobutyl have a shelf life?
Because it slowly dehydrohalogenates, particularly in warm storage, which changes its cure behaviour. Cool storage below 30 °C and first in, first out stock rotation are important in a way they are not for most elastomers.
Is butyl rubber hazardous?
No. It is an inert polymer not classified as dangerous goods. The practical hazards are manual handling of bales, rubber process fume during mixing, and hydrogen halide release if halobutyl is overheated.
Why is butyl used for pharmaceutical stoppers?
Because it combines very low moisture and gas permeability with chemical inertness and low extractables, protecting the drug product. Pharmaceutical grades are made and tested to USP, EP and JP requirements.
Can butyl rubber be used with oils or fuels?
No. Butyl swells badly in hydrocarbons. Nitrile rubber is the standard choice for oil contact, and fluoroelastomers for aggressive fuels at temperature.
What packing sizes are available?
25 to 35 kg bales wrapped in polyethylene film, palletised or in wooden crates, shipped in containers. Orders run from a pallet of bales up to full container loads.
Ready to source Butyl Rubber?
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.