Butyl Rubber
Butyl Rubber (IIR) is produced by copolymerizing isobutylene with small amounts of isoprene (typically 98% polyisobutylene and 2% isoprene). Butyl rubber was first commercialized in the early 1940s and hash excellent gas impermeability and air retention along with good flex properties.
Typical applications
- Air-tight seals
- Bladders in sports balls (football, basketball etc.)
- Gas masks
- It is impermeable to water and air (acts as barrier). It has good flex properties and good physical strength
- Poor flame resistance
- Poor oil resistance
- Poor compatibility with other polymers – low adhesion properties
| Available hardness range (Shore A) | 35 – 85 |
| Upper continuous service temp | 130°C |
| Min. temp. for sealing applications | -50°C |
| Minimum non-brittle temp | -70°C |
| Tensile strength (up to) | 18 MPa |
| Elongation at break (up to) | >700% |
| ASTM 1 Oil | None |
| ASTM 2 Oil | None |
| ASTM 3 Oil | None |
| Kerosene | None |
| Liquid B | None |
| Liquid 101 | None |
| Phosphate ester | Good |
| Ketone | None |
| Toluene | None |
| Iso-octane | None |
| Methanol | Excellent |
| Acid (weak) | Good |
| Acid (strong) | None |
| Base (weak) | Excellent |
| Base (strong) | Good |
| Hydrogen sulphide | Excellent |
| Steam | Good |
| Ozone | Good |
| Radiation | Good |
Frequently Asked Questions
What is Butyl Rubber?
Butyl rubber, also known as isobutylene-isoprene rubber (IIR), is a synthetic elastomer recognised primarily by its exceptional impermeability to gases and vapours. This characteristic makes it highly effective for applications requiring airtight seals. The rubber is a copolymer primarily composed of isobutylene with a minor proportion of isoprene, which enhances its flexibility and cure reactivity. One of the standout features of butyl rubber is its excellent resistance to heat, making it suitable for applications subjected to high temperatures. It also exhibits strong resistance to ozone and weathering, ensuring durability and longevity in outdoor or harsh environmental conditions. Additionally, butyl rubber demonstrates remarkable chemical stability, resistant to a wide range of aggressive chemicals including acids, alkalis, and other corrosive materials. This array of properties makes butyl rubber a versatile material in industries ranging from automotive (for tire inner linings and sealants) to pharmaceuticals.
What Are the Challenges Associated with Butyl Rubber?
Whilst butyl rubber offers excellent air and moisture barrier properties, it also presents several manufacturing challenges that need careful consideration. The most significant is its slow curing rate, which can lead to longer production times compared to other elastomers. This slow vulcanization process not only affects throughput but also requires careful temperature management to ensure that the rubber cures properly without degrading. Additionally, butyl rubber’s high viscosity and sticky nature make it challenging to handle during the moulding process, complicating tasks like material feeding and mould filling.
Another challenge with butyl rubber is its sensitivity to contamination. Trace amounts of impurities such as Sulphur, grease, and certain chemicals can severely affect the vulcanization process, leading to incomplete curing or compromised material properties. This requires stringent controls over the production environment and material handling practices. Furthermore, butyl rubber’s low green strength (its strength before curing) is another hurdle, as it can deform or get damaged during processing. These issues make it necessary for a high degree of precision in both the formulation of the rubber compound and the design of the moulding and curing processes. At Keaflex we implement stringent measures in our manufacturing process in order to mitigate these issues. For more information on how we combat issues associated with butyl rubber, please contact us directly.
What Are the Common Applications for Butyl Rubber?
Butyl rubber, known for its superior impermeability to gases and moisture, is utilised across various industries due to its robust properties. In the automotive sector, it’s primarily used for tire inner liners and weatherproof seals, enhancing vehicle insulation and reducing noise. The pharmaceutical and healthcare industries rely on butyl rubber for air-tight seals in medication vials, preserving the sterility of contents. It’s also favoured in consumer goods for sports equipment like air mattresses and protective gear such as gas masks, leveraging its air retention and protective qualities. In construction, butyl rubber serves as a critical material in sealants and roofing membranes due to its waterproofing capabilities and resistance to environmental wear. Additionally, its excellent dielectric properties make it suitable for insulating electrical cables, particularly in moisture-prone environments, underscoring its versatility and durability in demanding applications.
Are There Different Types of Butyl Rubber?
Yes, there are several different types of butyl rubber, each adapted for specific properties to suit particular applications. Regular butyl rubber, the standard form, is well known for its gas impermeability and chemical resistance, making it ideal for applications like tire inner liners and seals. For improved performance, bromobutyl rubber is enhanced with bromine to quicken its curing process and boost its heat, ozone, and chemical resistance, which is particularly advantageous in the pharmaceutical industry for making vial stoppers. Similarly, chlorobutyl rubber, modified with chlorine, offers better vulcanization properties and enhanced heat and chemical resistance, useful in automotive applications for tire liners and hoses where strong adhesion to metals is required. These variations are crucial in the rubber moulding industry, allowing manufacturers to choose the appropriate type of butyl rubber to meet the specific demands of different moulding projects.
How Does Butyl Rubber Compare to Other Synthetic Rubbers?
At Keaflex, we understand the importance of selecting the right material for each application, and butyl rubber (IIR) is one of the options we offer due to its unique properties. Butyl rubber is renowned for its excellent impermeability to gases and vapours, making it ideal for applications requiring air-tight seals such as automotive tire inner liners and air chambers. This rubber type also exhibits superior resistance to weathering, ozone, heat, and chemicals, which makes it suitable for a range of industrial applications that encounter harsh environmental conditions.
However, butyl rubber has a slower curing rate compared to other synthetic rubbers, which may require adjustments in processing times during manufacturing. It also has lower resilience and flexibility, which might limit its use in applications where dynamic flexibility and higher elasticity are crucial. In comparison to rubbers like natural rubber or SBR, butyl rubber offers distinct advantages in specific scenarios, particularly where durability against gases, heat, and chemicals is paramount. For detailed guidance on whether butyl rubber is suitable for your specific needs, please consult our technical team who can provide tailored advice based on your application requirements.
