Low Unsaturation Butyl Polymer for Curing Bladder

LANXESS Butyl RB 100 is a polymer well suited for curing bladder application.  Traditionally, regular butyl with a typical unsaturation value of about 1.85 mol % has been the preferred grade for use in curing bladder applications. This is attributed to the polymers excellent performance in applications requiring high temperature stability and excellent dynamic fatigue resistance. LANXESS Butyl RB 100 polymer, with an unsaturation level of 0.90 mol % can be used to further improve performance.  Preliminary investigations indicated that a simple mechanical blend of LANXESS RB 100 with the regular butyl grade provided a better overall balance of properties for a tire curing bladder compound.

This work was designed to investigate the effect of unsaturation level, plasticizer level, and resin curative level on the properties of a curing bladder compound.    It was found that reduced unsaturation level provides improved ageing stability and results in a smaller percent change of physical properties after hot air ageing.  Also, the use of Lanxess RB100 permits a reduction in the level of plasticizer which results in more tailored modulii values and an improvement in tension set.  A small reduction in resin level provides improved elongation values and improved flex properties, but tension set value is increased.  This laboratory data suggests that a bladder composition containing 25 phr of LANXESS RB 100, 7.5 phr level of phenolic cure resin and a 3.5 phr level of castor oil plasticizer will provide an excellent starting point formulation for a tire curing bladder application.