abstract
Silica-reinforced natural rubber (NR) tire tread compounds with epoxidized natural rubber
(ENR) as a compatibilizer are investigated. The ENRs consisting of 10, 38 and 51 mole%
epoxide are used in a range of 2.5–15.0 parts per hundred parts of rubber (phr). The addition
of ENRs, especially ENR-38 and ENR-51, decreases the Mooney viscosity, Payne effect,
flocculation rate constant and filler networking factor, which implies an improvement of
silica dispersion in the compounds. Chemically bound rubber contents and interaction
parameters of the compounds also increase with higher epoxide-contents of the ENRs, indicating
more interactions and/or reaction between the epoxide-groups of the ENR and silanol
groups on the silica surface. Tensile strength of the vulcanizates is improved with
increasing mole% epoxide, and the optimum value is observed at 7.5 phr of ENR-51. The
overall results show that silica-reinforced NR can be substantially improved by adding
ENR as a compatibilizer, when compared to a compound without ENR, but somewhat less
than with using a silane coupling agent.