Utilization of shield powder as a novel reinforcing and compatibilizing filler in styrene–butadiene rubber (SBR) composites

The reinforcement and compatibilization efficiency of shield powder (modified steel slag powder) for partial replacement of active calcium carbonate filler in styrene–butadiene rubber (SBR) composites was investigated in this work. It was found that the addition of shield powder could shorten the curing time, promote vulcanization process, improve mechanical properties and flame retardant properties of SBR composites. Besides, the optimal comprehensive performance was obtained when the shield powder replaced 60% active calcium carbonate, in which the torque increment (ΔM) was 4.94, being increased by 36.84%, the tensile strength was 11.96 MPa, being increased by 20.81%, the proportion of a stable weight residue at 700 °C was 17.02%, being increased by 13.27%. These phenomena show that shield powder plays a good reinforcing and compatibilizing effect in the SBR system. This is because the shield powder has a finer particle size and a large specific surface area, so that it can produce more crosslinking points with the rubber matrix, and the crosslinking density value with the rubber matrix becomes larger, while the modification of the silane coupling agent improves the compatibility of the shield powder/rubber and enhances the interaction between them. In addition, shield powder can form an effective physical barrier to hinder the transfer of oxygen and heat, while filling the small holes generated by combustion, adsorbed on the surface of carbon slag, promote the formation of secondary carbon layer, and improve the flame retardant performance of SBR composites.