Butyl

Butyl Rubber (IIR) — Overview & Key Properties

Butyl rubber is a synthetic elastomer produced by copolymerizing isobutylene with a small proportion of isoprene. In industry‑standard nomenclature, it is often designated as IIR (per ASTM D1418).

Traditionally used for sealing and gasketing, Butyl has in many cases been superseded by alternatives such as EPDM — but it still offers a unique set of properties that make it valuable for certain specialised applications.

Standard appearance: black rubber compound.

Why Use Butyl? Key Advantages

Butyl rubber stands out for several performance characteristics that make it particularly well‑suited to sealing, gasketing, and vibration‑damping applications:

• Exceptional impermeability to gases and vapours: Butyl’s molecular structure leads to extremely low gas permeability, making it ideal for airtight or vacuum‑seal applications — e.g., vacuum systems, compressed-air or gas sealing, and pneumatic/vacuum pipelines.
• Superior resistance to UV, ozone and environmental ageing: It resists degradation from sunlight, ozone exposure, and weathering — beneficial for both indoor and outdoor applications.
• Effective shock, vibration and sound damping: Its low resilience and viscoelastic nature give it good capacity to absorb mechanical shock and damp vibrations — useful for hydraulic seals, vibration‑isolating bushings, and other dynamic applications.
• Wide operational temperature range: Typical grades perform reliably across a broad temperature span (e.g. from about –40 °C to between +100 °C and +140 °C, depending on compound and product form).
• Good chemical and solvent resistance (selective): Butyl performs well against certain polar solvents and synthetic fluids, making it suitable for hydraulic systems that avoid mineral oils.

Because of this combination, Butyl remains an excellent choice for demanding sealing use cases — especially where gas retention, airtightness, environmental exposure, or shock absorption are priorities.

Typical Applications & Use Cases

Given its properties, Butyl is often used in:

• Vacuum sealing and compressed‑gas sealing – vacuum systems, compressed air or gas pipelines, pressure vessels, pneumatic equipment.
• Hydraulic systems using synthetic fluids / non‑mineral oils — as O-rings, seals or gaskets where mineral oils or aggressive hydrocarbons are not used.
• Gaskets and washers — especially in settings where low gas permeability or airtight sealing is required.
• Shock and vibration damping components — bushings, mounts, pads or vibration‑absorbing gaskets in equipment subject to dynamic loading or vibration.
• Sealing and waterproofing for external environments — such as waterproof membranes, linings, or sealing components exposed to weather, moisture or UV.

Typical Specification Range (Example — “Butyl 70”)

* As with all elastomers — actual usable range depends on compound specifics, age, environment, and exposure conditions.

How Butyl Compares to Some Alternative Materials

Compared to many general-purpose rubbers (natural rubber, basic nitrile, etc.), Butyl’s primary advantage lies in gas impermeability, environmental resilience (UV/ozone/weather), and shock/vibration damping.

However — if your application involves contact with oils, fuels, mineral-based lubricants, or aggressive hydrocarbons — then oils‑resistant elastomers (e.g. nitrile-based, fluorocarbon-based) or modified Butyl (chlorobutyl, bromobutyl) may be more appropriate.

Recommended Use – When to Choose Butyl

Choose Butyl when your sealing or gasketing application demands:

1. Airtight / gas-tight sealing — e.g. vacuum systems, gas retention, compressed-air lines.
2. Resistance to weather, ozone, UV or outdoor conditions — long-term exposure, external installations.
3. Shock and vibration damping, noise reduction, or mechanical stress absorption — hydraulic seals, vibration mounts, bushings.
4. Relative compatibility with polar solvents, synthetic fluids, or mild chemicals — but not with petroleum-based fluids.

If instead your application involves high exposure to oils, fuels, or hydrocarbon solvents — consider more oil‑resistant alternatives, or halogenated Butyl grades designed for improved chemical compatibility.

Compliance & Quality Considerations

At Eastern Seals (UK) Ltd, we source Butyl compounds from certified manufacturers, but because we may receive material from multiple approved suppliers, the actual compound batch, hardness, or performance characteristics may vary. The data provided here serves as a guide only — we strongly recommend that any purchaser verify compatibility and performance against their specific application requirements, particularly for critical sealing applications.

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Because it is a petroleum product, Butyl has poor resistance to hydrocarbon solvents and oils and diester-based lubricants. Halogenated Butyl has been introduced to expand oil and chemical resistance to this polymer. Chlorobutyl and Bromobutyl have better resistance. These polymers have been accepted by the medical industry for stoppers and septum’s for pharmaceutical applications.

Please note: This Material Data Sheet section is to be used as a professional guide only. Eastern Seals (UK) Ltd may source their products from a variety of Quality Approved Suppliers and the data shown should not be relied upon by any purchaser without verification of material source.

ES REF	Colour	Temp Range	Hardness	Notes	Data Sheet
BUTYL70	BLACK	-50°C to +110°C	70	Highly effective in vacuum sealing applications. Good seal for hydraulic systems.	BUTYL70 (IIR 70)