Effect of the Crosslink Density and Sulfur-Length on WET-Traction and Rolling Resistance Performance Indicators for Passenger CAR Tire Treads

 

The scope of this study is the investigation of the influence of different sulfur vulcanization systems for silica reinforced SBR/BR blends on the performance indicators of tire treads made thereof. Three series of compounds were prepared: with conventional, semi-efficient and efficient vulcanization systems. Each vulcanization system results in a specific overall crosslink density and different sulfur rank distribution: mono-, di- and polysulfidic of nature. The experimental results indicate that the influence of the overall crosslink density on the value of tan δ at 60 °C, an indication of rolling resistance, is higher than the type of crosslinks: A higher density of crosslinks reduces energy losses by limiting the segmental mobility of the polymer chains. Differences between the vulcanization systems manifest themselves only at relatively high strain levels, exceeding those used during measurements of the tan δ values at 60 °C. The dynamic mechanical analysis shows an increase in the glass transition temperature with rising overall crosslink densities. The influence of different crosslink densities on the LAT100 side force coefficient values, which are an indication of wet skid resistance of tire treads, is discussed in detail.