Enhancing tire tread performance with combined nano and micro-silica particles in styrene butadiene rubber/butadiene rubber compound

The influence of fumed nano-SiO ₂ on the performance of a typical tire tread compound, fabricated by mechanical mixing process, was investigated in the present research. The tire tread compound contained styrene-butadiene rubber (SBR)/ cis-butadiene rubber (BR) blend reinforced with a well-developed commercial highly dispersive silica filler at 70 phr loading. Nano-SiO ₂ with higher specific surface area, e.g., ∼240 m ² /g, was substituted partially with silica particle at three different concentrations of 5, 10, 15 phr. Improvement in various aspects of the control sample including crosslink density calculated based on the swelling test and tube theory, bound rubber content, and physico-mechanical properties was observed for nano-SiO ₂ loading below 10 phr due to its effective role in refinement of filler dispersion state and enhancement of rubber-filler interactions. However, most of the properties were sacrificed at 15 phr nano-SiO ₂ loading even with respect to the control sample which emphasized the effectiveness of nano-SiO ₂ within an optimum loading. Moreover, nano-SiO ₂ at optimum loading exhibited great improvement in initial decomposition temperature about 50°C, considerable improvement in rolling resistance (more than 8%) and enhancement in wear resistance which could be crucial for tire tread manufacturers.