Nanocarbon Black's Effect on Tribological Properties of a Hybrid Filler Tire Tread Compound Containing Modified Silica

Hypothesis: The use of nanocarbon black as the secondary filler in the hybrid filler system improves the tribological properties of tire tread compounds, such as abrasion resistance and coefficient of friction (COF), due to improvements in dispersion of modified silica as the primary filler. This improvement in the dispersion of primary filler is attributed to the barrier effect of secondary filler in flocculation of primary filler. Methods: A hybrid-filler system, modified silica as the primary filler with a fixed concentration and nanocarbon black with small concentrations as the secondary filler, were used to prepare tire tread compounds. The concentration of nano carbon black was kept below its percolation threshold based on previous studies. Vulcanization rheometry, scanning electron microscopy, dynamic-mechanical analysis in time, strain, and temperature sweeps were carried out to find the optimum amount of nanocarbon black. Tribological properties, including COF and abrasion resistance, were measured for the above hybrid filler compounds. Findings: The results showed that improvement in dispersion of modified silica was achieved by addition of 0.75 part per hundred rubbers as the optimum amount of nanocarbon black in a hybrid-filler system, and reduction in the nonlinear viscoelastic behavior or the Payne effect in rubber compounds confirmed the morphological synergy in the optimum hybrid filler compound. Tribological tests including COF and abrasion resistance of vulcanized rubber compounds showed an improvement in the compound with optimal amount of nanocarbon black. The measurement of storage modulus in strain sweep showed reduced flocculation of modified silica after mixing in the presence of nano carbon black. Tribological studies, including COF and abrasion resistance, showed improvement for the vulcanized compound with the optimum amount of nanocarbon black. Comparing the results with the reference compound, abrasion resistance was increased 30% and COF on wet concrete was improved 10% for the optimum compound.