Butyl Rubber Curing Bladder Resin Vulcanization Systems: Compositions and Optimization

A curing bladder is an important component of the tire vulcanizing press and the tire curing process. The proper selection of butyl polymers and compounding materials for the bladder formulation is essential in ensuring durability, required service life, and efficient curing bladder operation in a tire factory. This is due to the superior heat and steam resistance of resin cured butyl rubber which has resulted in its wide use for high heat resistant applications. Additionally, butyl rubber has very low permeability to gases and water vapor that further enhances the performance of butyl rubber tire curing bladders. Two resin based vulcanization systems are commonly used to cure bladder compounds. The two resin cure systems are each based on alkyl octylphenol formaldehyde. A non-halogenated alkyl octylphenol formaldehyde, which requires it to be compounded with a polychloroprene, is the more common system because of it ease of handling in a factory.  Brominated alkyl octylphenol formaldehyde does not require a halogen donor but is less common due to processing and high tack. The paper wishes to discuss the technical properties obtained with both vulcanization systems and how the microstructure of the butyl rubber molecule can affect these properties. The discussion will therefore provide an insight for the technologist on how to obtain the best performance from curing bladders in tire manufacturing operations.