Using low-rank coal slime as an eco-friendly replacement for carbon black filler in styrene butadiene rubber

Abstract We demonstrate a method for modifying low-rank coal slime for use as filler in styrene butadiene rubber (SBR). This method adds value to low-rank coal slime from the tailings of coal washeries and reduces environmental pollution caused by its disposal. The chemical and physical properties of coal slime powder were characterized after its modification by carbonization ball milling with sodium dodecylbenzene sulfonate. After this process, the particle diameter significantly decreased and the contents of O–H and C O bonds on the surface of the coal slime decreased, while those of C–O, COOR, and sulfonate groups increased. We then prepared composites of SBR and various coal slime powders and analyzed their morphology, mechanical properties, and thermal stability. Composites prepared with SDBS-modified coal slime filler showed enhanced reinforcement effect, with tensile strength of 18.27 MPa, which exceeds the value of 14.68 MPa for the composite with the widely used filler, carbon black N660 (CBN660). In addition, 5% mass loss occurred and the middle decomposition temperature increased by 28.11 and 20 °C, respectively, compared to those of pure SBR, and the values are also above the corresponding values for the composite with CBN660. Furthermore, coal slime with 30% ash content showed a biphasic uniform dispersion of the carbon/silicate filler as it reduced the bonding force between the filler particles and increased polymer–filler interactions, leading to a lower rolling resistance of the composite. The modified coal slime shows comprehensive reinforcement properties and is thus a suitable replacement for semi-reinforced carbon black.