Isobutylene-isoprene copolymer

Isobutylene-isoprene copolymer (CAS 9010-85-9), commercially known as butyl rubber, is a synthetic elastomer produced by copolymerizing isobutylene with a small proportion of isoprene. Its exceptionally low gas permeability and resistance to heat aging make it a preferred base polymer.

This material is utilized across demanding sealing and containment applications. In the tire industry, butyl rubber is the standard material for inner tubes and tubeless tire inner liners, where its low air permeability directly determines product performance and service life.

Automotive and industrial sealing components, including door seals, vibration dampers, and HVAC gaskets, rely on its long-term compression set resistance. These properties ensure durability and reliability in harsh operating environments over extended periods.

Pharmaceutical stoppers and closures for injectable drug packaging are manufactured from pharmaceutical-grade butyl rubber. These products are designed to meet strict extractables and permeation requirements for the healthcare industry.

Halogenated derivatives, specifically chlorobutyl and bromobutyl, extend its use into faster-curing tire sidewall compounds and adhesive formulations. These variants offer enhanced reactivity and compatibility with other elastomer types in complex blends.

Butyl rubber is supplied as bales, which is the standard commercial form for synthetic elastomers. Grades are differentiated by Mooney viscosity and isoprene content, with regular and halogenated variants available for specific cure system compatibility.

Technical and pharmaceutical grades are both commercially established. Pharmaceutical grades are subject to compendial specifications for closure applications, ensuring they meet the necessary safety and quality standards for medical use.