Butyl rubber, also known as isobutylene–isoprene rubber (IIR), is a synthetic material with a distinctive molecular structure. IIR is produced through the copolymerization of isobutylene (the main component) with a small amount of isoprene (typically below 5%). Owing to its very low degree of unsaturation, this polymer stands out for its exceptional gas impermeability, strong resistance to aging, and high environmental stability – making it an ideal choice across many industrial fields.
Key technical characteristics of Butyl rubber
The following physical and chemical properties underpin this material’s outstanding performance in specialized operating environments:
Extremely low gas permeability
Thanks to its tightly packed molecular structure and near-minimal unsaturation, IIR effectively prevents the diffusion of gases and moisture. Its gas permeability is about one-fifth that of natural rubber, helping maintain airtightness without additional reinforcement layers.
High chemical inertness
The material shows strong resistance to inorganic acids (H3PO4, H2SO4, HF, etc.) and many polar solvents (acetone, ethylene glycol, alcohols…). However, it is not suitable for environments containing petroleum derivatives or concentrated nitric acid. Because Butyl rubber is non-polar, it can interact undesirably with such media, leading to swelling and reduced chemical durability.
Resistance to aging and weathering
IIR maintains stability during prolonged exposure to ozone, UV radiation, and elevated temperatures. It resists surface cracking and retains mechanical performance even under harsh outdoor conditions.
Effective vibration damping
By absorbing and dissipating vibrational energy in the low-frequency range, the material significantly reduces vibration transmission through systems. Unlike highly elastic rubbers, Butyl’s damping arises from internal molecular friction that converts mechanical energy into heat.
Stable mechanical properties
High tensile strength, good tear resistance, and abrasion resistance help the material preserve structural integrity over time. Although its elasticity is lower than that of natural rubber, its elongation and resistance to deformation under load still meet common technical requirements.
Reliable electrical insulation
Due to its saturated, non-polar molecular structure, this material provides good electrical insulation. While not specialized for high-voltage uses like silicone rubber or EPDM, Butyl remains effective in medium-grade insulation systems.
Stable operation across a wide temperature range
IIR performs effectively from −50 °C to 120 °C. Certain specialized formulations – especially halogenated grades – can tolerate short-term temperatures up to 150 °C without compromising the polymer structure.
Classification of Butyl rubber and specialized variants
Beyond standard IIR, Butyl rubber has two principal variants created by introducing halogen atoms (chlorine, bromine, etc.) into the polymer chain:
- Chlorobutyl rubber (CIIR): Offers faster vulcanization and better adhesion; suitable for blending with other rubbers. Used in tire inner liners and heat-resistant conveyor belts.
- Bromobutyl rubber (BIIR): Excels in cure speed, adhesion, and cleanliness. Commonly used for pharmaceutical stoppers, high-performance tires, and medical devices.
Product lines labeled B-5, B-15, etc., are typically manufacturers’ trade names, categorized by molecular weight, isoprene content, specific additives, and so on, to optimize performance for particular uses – for example, strong acid resistance (B-115, B-215) or pre-vulcanized grades (B-5S, B-5BS).
Practical applications of Butyl rubber
Given the properties outlined above, Butyl rubber has proven highly versatile and long-lasting across numerous industries. Representative applications include:
- Automotive and tire manufacturing: The standard material for tire inner liners to maintain stable air pressure. It also appears in vibration-damping parts, hoses, and acoustic insulation panels in vehicles.
- Chemical industry and flue-gas treatment: Used for lining acid storage tanks, flue-gas desulfurization (FGD) towers, and equipment in direct contact with corrosive gases or liquids.
- Healthcare and food industries: Commonly used to produce vial stoppers, capsule films, and medical gloves thanks to its gas impermeability and absence of harmful impurities.
- Construction and acoustic engineering: Owing to excellent damping, sealing, and sound-insulating properties, IIR is applied in floor liners, acoustic wall panels, noise-barrier partitions, and various civil engineering components.
Usage notes
To achieve peak performance and extend service life, observe the following technical considerations:
- Cutting and forming should be done with sharp tools to avoid edge tearing or surface scratches.
- Processing temperatures must follow the technical specifications, especially for unvulcanized grades.
- Some products may emit a characteristic odor; ensure good ventilation in storage and work areas.
Butyl rubber delivers high industrial value by combining impermeability, chemical resistance, mechanical strength, and long-term stability. Selecting the right grade and appropriate processing method will help optimize performance and reduce operating costs. For in-depth consultation, please contact Thai Duong Plastics for detailed support.