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Low Unsaturation Butyl for Demanding Service Applications
The inherent stability of the isobutylene moiety in isobutylene-isoprene copolymer, commonly referred to as regular butyl makes it particularly resistant to thermal and oxidative degradation. Regular butyl with a typical unsaturation value of about 1.85 mol % offers heat resistance for dynamic rubber applications requiring a good balance of mechanical strength and elasticity. In addition, when a phenol formaldehyde resin cure is used with butyl, the crosslinks are very stable toward heat and oxidation therefore are used in extended high temperature service above 150 °C. However, the drawback to resin systems produce vulcanizates that suffer from some hardening while in service via resin continuous crosslinking of residual unsaturation in the polymer.
The low unsaturation of butyl vulcanized with resin tends to be slow, so halogen bearing activators are normally used to increase the rate of cure.
LANXESS Butyl RB 100 polymer with an unsaturation level of 0.90 mol % can be used to further improve dynamic service performance. This work was designed to investigate the effect of unsaturation level and halogen bearing activators on the balance of physical properties for service life. This laboratory data suggests that a mechanical polymer blend of low unsaturation butyl with high unsaturation butyl can mitigate the effect of in service hardening. In addition, an optimal amount of polychloroprene will provide an opportunity to improve on mechanical strength properties without compromising the heat resistant properties of mechanical goods using regular butyl for improved service life.