Using heat-treated starch to modify the surface of biochar and improve the tensile properties of biochar-filled styrene–butadiene rubber composites:

Heat-treated starch (HTS) is a renewable material that can be used to modify the surface chemistry of small particles. In this work, HTS was used to coat hydrophilic biochar particles in order to make them more hydrophobic. Then, when added as filler to hydrophobic styrene–butadiene rubber (SBR), the coated biochar dispersed more easily and had enhanced filler–matrix interactions, which were reflected in the tensile properties of the final composites. Biochar particles modified with 5% (weight) HTS showed increases of 59% in the ultimate tensile strength, 49% in elongation percentage, and 79% in fracture toughness of SBR composites compared to unmodified biochar particles. This shows that HTS can be used to improve the tensile properties of composites filled with biochar and potentially other hydrophilic filler materials.