IIR
Butyl Rubber
Glass Transition (Tg)
-70 to -65 °C
Melting Point (Tm)
—
Density
0.92 g/cm³
CAS Number
9010-85-9
Recycling Code
None
Category
Elastomer
Repeat Unit
–[CH₂–C(CH₃)₂]ₓ–[CH₂–C(CH₃)=CH–CH₂]ᵧ–
The repeating unit is the smallest structural fragment whose repetition builds the whole chain. Subscripts show the relative share of each unit in copolymers.
Key Properties
Exceptionally low gas permeability (~10× lower than NR) and high damping; slow to cure and difficult to bond.
Applications
Tyre inner liners, pharmaceutical vial stoppers, vibration damping.