Abstract
Modern passenger car tire tread compounds usually consist of a polymer blend of Solution Styrene-Butadiene Rubber (SSBR) and Butadiene Rubber (BR) in combination with a silica/silane system. To further enhance the compatibility between the nonpolar polymer and the polar silica, different functional groups can be introduced at the end or along the polymer chains. The influence of such a polymer functionalization of SSBR and BR on the processing behavior as well as on mechanical and dynamic properties was investigated for silica-filled tire tread model compounds. Silica-filled functionalized SPRINTAN™ SLR 4602 was blended with non-functionalized SPRINTAN™ 363H and functionalized SPRINTAN™ 884 L 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 (Tg) and functionalization. All five properties influence the composite properties in a different way. The functionalization is the dominating influencing parameter in this study. The presence of the functionalization improves the rubber-filler-interaction. This leads to better dynamic and mechanical properties of the model tread compound: 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. Furthermore, the Tg of the whole blend compound dominates the dynamic-mechanical behavior, as expected. In the case of BR, the functionalization has the dominating influence on the tan δ, the effect of Tg plays a minor role. These new insights support the development of new functionalized polymers to improve the overall tire performance.
Highlights
In the last years, the European Union (EU) has mandated the reduction of the greenhouse gas emissions, especially carbon dioxide (CO2)
The two types of Butadiene Rubber (BR) differ in five analytical properties: molecular weight, vinyl content, cis-content, glass transition temperature (Tg) and type of functionalization
Silica-filled functionalized SBR-4602 rubber compounds were blended with non-functionalized BRs SPRINTANTM 363H (BR-363) and functionalized BR-884 in three ratios: 90/10, 80/20 and 70/30
Summary
The European Union (EU) has mandated the reduction of the greenhouse gas emissions, especially carbon dioxide (CO2). One example is the production of function alized Solution Styrene-Butadiene Rubber (SSBRs) [4,5] This polymer type is produced by anionic solution polymerization initiated by an organo-lithium (Li) catalyst. It is possible to react the chain-ends of the monomer with a polar group, because the reaction of the chain-ends with another growing monomer chain rarely occurs. This can significantly change the rheological or chemical properties of the polymer. Chain-end func tionalized polymers can be produced which can affect the polymer-filler interaction already in the unvulcanized stage and influence the hysteretic properties of the rubber compound [4]. The rolling resistance and wear resistance of the tire tread deteriorate due to the lower chain mobility [8]
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