Tailoring biochar production for use as a reinforcing bio-based filler in rubber composites: a review

Biochar is gaining popularity as a reinforcing filler in composite manufacturing. Applied to rubber composites, biochar shows potential as a greener filler, but is not yet a drop-in substitute for fillers like carbon black. Through optimizing the pyrolysis process, biochar may be engineered to have ideal filler characteristics. This review identifies the key properties of highly reinforcing filler materials as particle size, structure, and surface activity. It subsequently focuses on the techniques to optimize biochar for applications as a rubber-reinforcing filler. Finally, the mechanical performance of biochar as a filler in rubber is reviewed and compared with industry-adopted reinforcing fillers.