Comparative Study of CB, Silica and CB/Silica Filled SBR Extended By Norbornylized Soybean Oil

Carbon black (CB) and precipitated silica are two major reinforcing fillers in rubbers. CB/silica hybrid filler is also widely used in rubbers to provide balanced properties. CB/silica hybrid filler-filled SBR compounds and vulcanizates containing conventional naphthenic oil (NO), soybean oil (SO), and norbornylized SO (NSO) are investigated. Swelling and curing behavior, rheological, mechanical, thermal, aging, and dynamic properties are studied and compared with earlier reported data on CB- or silica-filled SBR. It is found that the addition of SO and NSO increases the gel fraction, but decreases the crosslink density of SBR vulcanizates. NSO provides better scorch safety and faster cure than SO. The addition of SO and NSO enhances the thermal stability and aging resistance of SBR vulcanizates compared with SBR/NO vulcanizates. The SBR/NSO vulcanizates with hybrid filler exhibit a higher tensile and tear strength than those of the SBR/NO and SBR/SO vulcanizates. Synergetic effect in vulcanizates containing the hybrid filler is observed for abrasion resistance. An increase of sulfur content provides the SBR/NSO vulcanizates with improved abrasion resistance and loss tangent values predicting improved wet traction and rolling resistance.