Influence of the silica content on theological behaviour and cure characteristics of silica-filled styrene-butadiene rubber compounds

Rheological behaviour and cure characteristics of silica-filled styrene-butadiene rubber (SBR) compounds and SBR compounds filled with both silica and carbon black with different silica contents were investigated. Rheocurves of the time versus the torque of the compounds showed specific trends with the silica content. For the compounds with low silica content (less than 50phr), the torque decreased immediately after the steep increase at the initial point of the rheocurve and then increased very slowly. For the compounds with high silica content (more than 50phr), the rheographs showed two minimum torque points; the torque decreased immediately after the steep increase at the start point of the rheocurve and then increased sharply before reaching the second minimum point. This can be explained by the strong filler-filler interaction of silica. The minimum torque of the compound increased slightly with an increase of the silica content up to 50phr silica content and then increased appreciably. For the silica-filled compounds, cure times of the t(02), t(40), and t(90) became shorter with an increase of the filler content. For the compounds filled with both silica and carbon black (total filler content of 80phr), the cure times became longer with an increase of the silica content ratio. (C) 2001 Society of Chemical Industry.