Use of epoxidized natural rubber as a compatibilizer in silica-filled natural rubber tire tread compounds = Verwendung von epoxydiertem Naturkautschuk als Verträglichkeitsvermittler in Zusammensetzungen aus kieselsäuregefülltem Naturkautschuk für Reifenlaufflächen

Silica-reinforced natural rubber (NR) tire tread compounds with epoxidized natural rubber (ENR) as a compatibilizer are investigated. ENR contents of 2.5-15.0 phr, with epoxide levels of 10, 38 and 51 mol%, are used. The addition of ENRs, especially ENR-38 and ENR-51, as compatibilizers decreases the Mooney viscosity and Payne effect (i.e. filler-filler interaction), which implies an improvement of silica dispersion in the compounds. Chemically bound rubber contents of the compounds, indicative for interaction/reaction between the epoxidegroups of the ENR and silanol-groups on the silica surfaces, also increase with higher epoxide-contents of the ENR. Raising the ENR contents and mole% of epoxide prolongs cure and scorch times of the silica-filled compounds, when compared with a silica-filled NRcompound without ENR. Tensile strength of vulcanizates is improved with increasing mole% of epoxide, and an optimum value is observed when 7.5 phr of ENR-51 was used. The results show overall, that the properties of silica-reinforced NR can be substantially improved by adding ENR as a compatibilizer, when compared with a compound without.