Structural Influences Of Silane Coupling Agents On The Dynamic Properties Of A SBR / Silica Tire Tread Compound

The elastomer compound used for tire treads is a composite material of which the dynamic properties can be adjusted over a relatively broad range by modification of the polymer-filler interaction. The replacement of carbon black by a silica-silane system, for instance allows reducing the hysteresis of the rubber, which results in a reduction of the rolling resistance when applied for tire treads. Selective changes in the structure of the coupling agent, e.g. the number of alkoxy groups reactive towards silanol groups on the surface of the filler, the length of the linker between filler and polymer, or the bond strength between coupling agent and polymer, lead to changes in the microstructure of the silica-polymer interface and determine the dynamic properties of the material, thus wet grip and rolling resistance of a tire tread. It was shown that these changes in the silane structure lead to characteristic changes in the properties of the composites. Silanes with just one ethoxy group instead of three as in the commonly used silanes decrease the hysteresis at high temperatures and increase it at low temperatures. A longer linker lowers the hysteresis at elevated temperatures, thus a lower energy loss at the service temperature of a running tire. When the silane molecule cannot chemically link to the polymer, the dynamic as well as the mechanical properties deteriorate. In this paper, the effect of specific changes in the structure of the silane coupling agent on the macroscopic dynamic properties as indicators for tire performance will be discussed.