Fillers for Reduced Tread Hysteresis

Transportation accounts for most of the consumption of petroleum in the modern world, and within the transportation sector, trucks and buses consume about 20% of the total. This equates to about 39 billion gallons of fuel per year in the USA alone. There is a strong desire to reduce this consumption for cost reasons, and also to preserve limited resources and to reduce carbon dioxide emissions. Tire rolling resistance is a significant contributor to the fuel consumption in commercial vehicles, and within the tire, the tread compound has the greatest effect. We have shown that by reducing the hysteresis in truck tread compounds, we do see a correspondingly lower rolling resistance in tire tests. We describe two approaches to reducing the hysteresis in natural rubber-based tread compounds based on new filler materials. The first is using carbon-silica dual phase fillers. With these materials, we found that the reduction in hysteresis was disproportionately large compared to the amount of silica in the filler particles. This enables significant reduction in hysteresis at low silica content, which meant that the good wear-resistance properties of carbon black could be maintained. The other type of filler studied was carbon black with broad aggregate size distribution. For both of these new filler technologies, the hysteresis improvements were demonstrated in the laboratory using dynamic mechanical property measurements, and validated by truck tire testing. The effects are explained based on the concepts of filler networking.