Influence of Functionalized Polymers on the Processing Behavior and In-rubber Properties of Passenger Car Tire Tread Compounds

Modern passenger car tire tread compounds usually consist of a polymer blend of Solution Styrene-Butadiene Rubber (SSBR) and Butadiene Rubber (BR). This polymer system, in combination with precipitated silica and bifunctional organosilanes, leads to improved tire properties such as wet traction (safety) and rolling resistance (fuel consumption). To further enhance the compatibility, and therefore the performance, of non-polar polymers with high reinforcing polar fillers, different functional groups are introduced to the base polymers. This influence of polymer functionalization of SSBR and BR on the processing behavior as well as mechanical and dynamic properties was investigated for silica filled tire tread model compounds. Therefore, silica-filled functionalized SPRINTAN TM SLR 4602 were blended with non-functionalized SPRINTAN TM 363H and functionalized SPRINTAN TM 884L in three ratios: 90/10, 80/20 and 70/30. The two BRs differ in five analytical properties: molecular weight, vinyl content, cis-content, glass transition temperature (T g ) and functionalization. All five properties influence the composite properties in a different way. The study showed that the functionalization is the dominating influencing parameter. Furthermore, the T g of the whole blend compound dominates the dynamic-mechanical behavior, as expected. In the case of the BR, the functionalization has the dominating influence on the tan δ , the effect of T g plays here a minor role. The presence of the functionalization improves the rubber-filler-interaction. This leads to better dynamic and mechanical properties of the model tread compound. Hence, the reinforcement index is increased and the tan δ at 60°C, as lab predictor for the tire rolling resistance, is reduced while the tan δ at 0°C, as lab predictor for wet grip, is similar to the non-functionalized BR. These new insights support the development of new functionalized polymers to improve the overall tire performance.