The physicochemical properties of biochar and its applicability as a filler in rubber composites: A review

Fillers in rubber composites are nanomaterials known for their reinforcing properties in elastomer matrices. Carbon black, a non-renewable material, is currently the preferred filler in the rubber tire industry. In recent years, biochar has become of interest as a potential replacement filler for carbon black in rubber applications. The wide range and varying nature of feedstocks, and the flexibility of the pyrolysis operating conditions yield biochar with diverse and distinct physicochemical properties. The primary aim of this review is to provide an overview of the effect of the feedstock source and the process parameters on the physicochemical properties of the resulting biochar. In addition, the inherent properties of carbon black will be compared to the general properties of biochar as a mean of determining biochar's suitability as an alternative filler. Finally, biochar's mechanical performance will be compared to the reinforcing ability of carbon black.