Reactive Mixing As a Way of Grafting Onto Silica Surface with Epoxidized Polymers

Lightly epoxidized cis-polybutadiene (EpBR) was prepared and used to react in situ with precipitated silica in an internal mixer in passenger tire tread formulations. Previous studies of differential scanning calorimetry (DSC) showed that the required amount of epoxy groups to react with the silanols on the silica surface was 6,8 mmol/m², agreeing closely with the dynamic mechanical analysis (RPA) of the vulcanized compounds. The rubber-filler interaction was characterized by investigating processing characteristics, the filler dispersion, the bound rubber content and the mechanical and dynamic properties of the vulcanizates. It was evidenced that the grafting onto silica surface with EpBR could be easily monitored during the mixing process and the reaction rate could be controlled by varying the temperature and rotors speed. It was also observed an increase in the bound rubber content proportional to the amount of epoxidized polybutadiene added. Due to the more efficient polymer-filler interactions, compounds containing EpBR–grafted silica showed Payne Effect 40% lower and higher tand at low temperatures than the analogous ones were bis(triethoxysilylpropyl) tetrasulfane (TESPT) was employed as coupling agent.