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General product and material information only; this page is not medical advice and does not describe any clinical procedure.
Short answer
Butyl rubber (IIR) is a synthetic rubber made by copolymerizing isobutylene with a small fraction of isoprene. It is valued for very low permeability to air, gases and moisture, and for good resistance to ageing, heat, acids, bases and ozone. It is not resistant to everything: mineral oils, grease, fuels and chlorinated hydrocarbons attack it.
Definition and scope
Regular butyl rubber is a copolymer of isobutylene and a small amount of isoprene, 0.5 to 2.5 mol% according to producer ARLANXEO. The isoprene provides unsaturation, which is what allows the rubber to be vulcanized (cured). Parker Engineered Materials Group describes the same isobutylene-isoprene composition and notes the material was first introduced in the early 1940s.
Three terms are easy to confuse. Butyl rubber is the elastomer itself. A butyl glove is a protective glove made from it, covered separately in butyl gloves. Halogenated versions (halobutyl) are chemically modified forms of the same polymer, described below.
How it is used in practice
ARLANXEO lists tire inner liners and inner tubes, curing bladders, window sealants, damping mounts, hoses and seals among the uses of butyl and halobutyl rubber, and also medical and pharmaceutical products: stoppers for infusion containers, injection vials and blood collection tubes. Parker describes pharmaceutical stoppers, syringes and closures as applications for chlorobutyl and bromobutyl.
The reason is the polymer structure. ARLANXEO states that butyl rubber adopts a densely packed structure that gives excellent impermeability to gases, one of its defining characteristics. Parker adds that using butyl rubber allows the stopper to reseal after being breached by a needle.
Butyl rubber properties
- Low permeability: impermeability to air and moisture, with high density (ARLANXEO, Parker).
- Damping: high damping of low-frequency vibrations (ARLANXEO).
- Ageing and weathering: good resistance to ageing, heat and ozone (ARLANXEO); ozone resistance is called out by Parker as especially important.
- Temperature range: Parker states heat resistance up to 120 °C and low-temperature flexibility down to -59 °C. Grades and compounds differ, so treat these as one manufacturer’s general figures rather than a specification for a particular product.
- Steam and hot water: compatible with hot water and steam (Parker).
Types: regular butyl and halobutyl
ARLANXEO explains that butyl can be halogenated with chlorine or bromine to give chlorobutyl (CIIR) and bromobutyl (BIIR). Parker groups these two as halobutyls.
| Type | What it is | Sourced notes |
|---|---|---|
| Butyl (IIR) | Isobutylene with 0.5 to 2.5 mol% isoprene | Low permeability; vulcanized through the isoprene unsaturation (ARLANXEO) |
| Chlorobutyl (CIIR) | IIR halogenated with chlorine | Used in tires and inner tubes, hose, gaskets, pharmaceutical stoppers and syringes (Parker) |
| Bromobutyl (BIIR) | IIR halogenated with bromine | Very similar to CIIR with a greater choice of curatives (Parker); bromobutyl is used in pharmaceutical closures (Parker) |
According to ARLANXEO, halogenation allows co-vulcanization and better compatibility with other diene rubbers and improves vulcanization rates, state of cure and reversion resistance. It also states that halogenated butyl is generally preferred for medical and pharmaceutical stoppers and is often the choice for them because of its cleanliness and good resealing properties.
Butyl rubber chemical resistance: what it resists and what it does not
Chemical resistance is the property most often misread, so it helps to look at both sides. The lists below come from Parker’s chemical resistance summary.
| Generally compatible | Not compatible |
|---|---|
| Hot water and steam | Mineral oils and grease |
| Many acids and salt solutions | Fuels |
| Polar solvents | Chlorinated hydrocarbons |
| Glycol-based brake fluids | |
| Silicone oils and greases | |
| Ozone |
Parker compares butyl with EPDM: the chemical compatibility is similar, but EPDM has a higher temperature resistance. For protective gloves, butyl is one of several materials; see chemical-resistant glove selection and chloroprene gloves for how they compare.
Where it matters for labs and clinics
- Vial and blood-tube closures. ARLANXEO identifies butyl-family stoppers for injection vials, infusion containers and blood collection tubes, and Parker states that butyl rubber allows the stopper to reseal after being breached. Regular, chloro- and bromobutyl are different members of the same material family.
- Chemical contact. Parker lists mineral oils and grease, fuels and chlorinated hydrocarbons as not compatible with butyl. Compatibility data differ by compound, so manufacturers publish their own figures.
- Gloves and PPE. Glove selection depends on the chemical, as set out in the PPE selection for chemical handling guide and the broader lab safety equipment checklist.
Common misunderstandings
- “Chemical resistant” does not mean universally resistant. Butyl handles acids, bases, ozone and steam but not fuels, mineral oils or chlorinated hydrocarbons.
- Butyl rubber is not the same as a butyl glove. The glove is one product made from the material, and glove performance is judged against the specific chemical.
- Butyl and halobutyl are not interchangeable labels. Halogenation changes curing behaviour, and manufacturers describe halobutyl as the usual choice for pharmaceutical stoppers.
- One temperature figure is not a specification. Published ranges come from manufacturers’ general descriptions and vary by compound.
FAQ
What are the properties of butyl rubber?
Low permeability to air, gases and moisture, high damping of low-frequency vibration, and good resistance to ageing, heat, acids, bases and ozone, per ARLANXEO and Parker. It is compatible with hot water and steam (Parker).
What is butyl rubber chemical resistance?
It is compatible with many acids, salt solutions, polar solvents and steam, but not with mineral oils and grease, fuels or chlorinated hydrocarbons (Parker).
Sources
- ARLANXEO, Regular Butyl and Halogenated Butyl Rubber (X_Butyl), checked 30 October 2026.
- Parker Engineered Materials Group, IIR and Butyl: Little Known Low Permeability Options for Drug Delivery and Blood Collection Applications, Part 1, checked 30 October 2026.
