BUTYL (IIR) Isobutylene-isoprene
Advantages: Outstanding impermeability to gases and vapor; very
good resistance to heat, oxygen, ozone, and sunlight; high energy absorption
(damping); excellent resistance to alkalis and oxygenated solvents; good hot
tear strength; superior resistance to water and steam.
Limitations: High compression set; poor resistance to oil,
gasoline, and hydrocarbon solvents; low rebound elasticity (snap); fair
processability, poor resilience.
Comment: Butyl is chemically unlike natural rubber or other
synthetic elastomers in that it is inherently resistant to ozone and corrosive
chemicals, including some mineral acids, ketones, and phosphate-ester-type
hydraulic fluids. On the negative side, its creep, cold flow, and compression
set characteristics leave much to be desired. The processing properties of butyl
are only fair. Because of its low level of unsaturation, buytl is difficult to
break down during mixing, and it is very susceptible to contamination. Slight
contamination causes improper cure and poor physical properties. Chlorinated and
brominated versions are less susceptible to contamination and offer lower
compression set and improved heat resistance.
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http://www.moldeddimensions.com/generalpolymers.htm
