Valorization of biomass waste: hemp- derived biochar to improve wear and fire resistance of polymer composites

This study investigates the use of biochar, derived from waste hemp hurd and hemp fibers, as reinforcing filler to improve thermal conductivity, mechanical and flame retardant properties of ethylene vinyl acetate (EVA). EVA/fiber biochar (HFB) composites with different fiber loadings (from 5 to 40 wt.%) showed an enhanced thermal conductivity (increasing from 0.33 to 0.40 W·m−1·K−1). The combination of stiffness, intrinsic lubricating properties of the filler, and enhanced thermal conductivity resulted in excellent wear resistance and friction reduction in the composites compared with unfilled EVA. Hemp hurd biochar (HHB) enhances the fire retardant properties of the EVA composites, decreasing both peak of heat release rate (pkHRR) and total heat release (THR), especially at the highest filler loading (i.e., 40 wt.%).