Generally know as butyl rubber.
Butyl compounds have similar chemical resistance to ethylene-propylene. They display excellent resistance to air, water, dilute acids and alkalis; plus resistance to aliphatic phosphate-ester hydraulic fluids, salt solutions, alcohols, glycols and silicone oils.
Resistance to hydrocarbons is poor: butyl must not be used with mineral oils.
Typical operating temperatures
-35°C to +120°C continuous, or to +150°C intermittent.
Fluid sealing duties
Very low gas permeability makes butyl popular for vacuum and high pressure gas applications.
Supplied in grades of 60-70 IRHD.