disclosed are expandable bladders for use in curing presses for rubber compositions such as pneumatic tires . the bladders are a crosslinked elastomer comprising an isobutylene rubbery polymer . the bladder composition includes alkylphenoxypoly - alkanol which improves the release characteristics of the cured bladder from a tire innerliner cured in contact with said bladder . the improved release characteristics allow rubber compositions such as tires to be molded with fewer defects caused during release of the bladder from the tires or caused by abraded or deformed bladders . the use of alkylphenoxypolyalkanol also increases the useful life time of the bladder allowing more tires to be cured without changing bladders .