Upcycling automotive recyclate and miscanthus derived-biocarbon for sustainable composite in automotive applications

We develop impact-toughened sustainable composites from recycled polypropylene (r-PP) obtained from waste automotive parts, pyrolyzed miscanthus biomass (biocarbon) as a filler, and maleic anhydride-grafted polypropylene (MAPP) as a compatibilizer. rPP was blended with an ethylene-octene copolymer (EOC) to improve impact resistance. Biocarbon and MAPP were added to recover stiffness and enhance thermal/dimensional stability. The addition of EOC to the biocarbon-filled composite improved notched Izod impact strength by 21%. Adding 20 wt% biocarbon increased the tensile and flexural moduli by 17% and 10%, respectively, lowered the coefficient of linear thermal expansion (CLTE) by ~11% in the flow direction and ~17% in the normal direction, and increased the heat deflection temperature by 18%. Density remains ≤ 1 g cm⁻³ with a total sustainable content of 75 %. A simple micromechanical model was used to extract a reinforcement efficiency factor , which increased from 0.55 (uncompatibilized BioC composite) to 0.95 with MAPP, indicating significantly improved filler dispersion and interfacial stress transfer. Biocarbon and MAPP synergistically enhance interfacial stress transfer and restrict chain mobility, enabling the formation of tougher, stiffer, and thermally stable rPP-based composite materials with increased sustainability by using recycled polymers and bio-derived filler for non-structural automotive components.