Butyl rubber is a copolymer of isobutene and a small proportion of isoprene (0,5-3%). This provides a double-bond to the polymer and permits curing with sulfur and other curing systems. Butyl rubber is not cured with peroxide since this tends to break down the rubber. Like EPDM it possess good resistance to chemicals, polar fluids and ozone as well as good electrical insulation. Other special properties of IIR are low gas and moisture permeability and high shock absorption. These properties have made butyl rubber the polymer choice in a variety of applications.

Cure system – Sulfur Cured

Standard IIRs are sulfur-cured.

Other Common Variations

  • Can be formulated using only “white list” ingredients as specified in 21.CFR 177.2600 for application where the elastomer will be in contact with food or beverages.

General Information

ASTM D 1418 Designation: IIR, CIIR, BIIR
ISO/DIN 1629 Designation: IIR, CIIR, BIIR
ASTM D2000 / SAE J 200 Codes: AA, BA
Standard Color(s): Black
Hardness Range: 50 to 80 Shore A
Relative Cost: Low

Service Temperatures

Standard Low Temperature: -55°C / -67°F
Standard High Temperature: 100°C / 212°F

Performs well inDoes not perform well in
AlcoholsAliphate and aromic hydrocarbons
KetonesHalogenated solvents
Dilute acids and alkalisPetroleum based oils and greases
Silicone oils and greases
Water and steam
Phosphate ester based hydraulic fluids – Skydrol®
Ozone, aging and weathering