Waste biomass-derived rubber composite additives: Review of current research and future investigations into biowaste tire formulation

Rubber composites are highly engineered materials composed of a multitude of additives in addition to natural and/or synthetic rubber. For tire production, these additives range from reinforcing fillers, to processing aids, to protectants, to cross-linking systems. Current commercial additives are generally sourced from petroleum sources, including carbon black and various petrochemicals. As research into more sustainable production practices has increased considerably in recent years, identifying and developing effective bio-sourced alternatives to these components of tire rubber composites warrants investigation. Waste biomass is an attractive raw material source as it is readily abundant and cost-effective. Current research has shown that waste biomass can be used to produce compounds that have similar physical and chemical properties to many rubber additives. Some have demonstrated efficacy in polymer formulations, while others have developed these components for entirely different applications. This review overviews additive types in rubber tire composites, their function, the current commercial fillers used, discusses current novel biowaste alternatives, and develops hypothetical candidates for future investigation.