Tire curing bladder with improved release characteristics

An expandable curing bladder being the molded crosslinkstar from a formulation comprising:

• one or more rubbery polymers, wherein at least 50 weight percent of said rubbery polymers are at least one isobutylene rubbery polymer having at least 80 weight percent units from isobutylene;
• wherein at least 10 weight percent of said at least one isobutylene rubber polymer is one or more copolymers of isobutylene and para-alkylstyrene;
• from about 1 to about 20 phr of corn oil dispersed throughout said bladder and wherein said corn oil reduces the Hot Peel Adhesian value of said crosslinked bladder formulation at least 10 percent as compared to the same bladder formulation without said corn oil;
• and
• one or more curatives for said rubbery polymers;
• wherein phr is parts by weight based upon 100 parts by weight of said one or more rubbery polymers in said bladder.

A method of using an expandable rubber bladder to cure an uncured rubber composition, said method comprising the sequential steps of:

• first inserting an uncured rubber composition into a curing press having an expandable rubber bladder positioned therein and having one or more molding surfaces;
• second expanding said expandable rubber bladder by filling the internal portion of said bladder with a fluid to expand the bladder outwardly against an inner surface of the uncured rubber composition to force said uncured rubber composition against said one or more molding surfaces and curing the rubber composition into a cured article under conditions of heat and pressure;
• and
• third deflating said expandable rubber bladder and removing the cured article from said curing press,
• the improvement wherein the expandable bladder is a molded and crosslinked rubber formulation wherein said rubber formulation comprises:
• one or more rubbery polymers, at least 50 weight percent of said rubbery polymers being at least one rubbery isobutylene polymer having at least 80 weight percent repeat units from isobutylene, and wherein at least 10 weight percent of said at least one isobutylene rubbery polymer is one or more copolymers of isobutylene and para-alkylstyrene;
• and
• from about 1.0 to about 20 parts by weight of corn oil dispersed throughout said bladder and wherein said corn oil reduces the Hot Peel Adhesion value of said crosslinked bladder formulation at least 10 percent as compared to the same bladder formulation without said corn oil;
• wherein said parts by weight are based upon 100 parts by weight of said one or more rubbery polymers in said bladder.