Effect of carbonization temperature on mechanical properties and biocompatibility of biochar/ultra-high molecular weight polyethylene composites

Highly filled biochar/ultra-high molecular weight polyethylene (UHMWPE) composite samples with excellent mechanical properties and biocompatibility were prepared via extrusion followed by hot-compression. Biochar carbonized at 500 °C (BC500), 800 °C (BC800), and 1100 °C (BC1100) at 70 wt% loading were used to reinforce UHMWPE. During the melt compounding process, UHMWPE molecular chains infiltrated the nanoscale pores of biochar particles and formed strong interfacial bonds through mechanical interlocking and van der Waals forces between the BC particles and the UHMWPE resin. The composite containing BC500 exhibited the best tensile strength (54.7 MPa), wettability, and biocompatibility, while the composite containing BC1100 showed the highest hardness and modulus (>2.1 GPa), and the lowest friction coefficient and water absorption rate. The property variations of the composites were attributed to the difference in biochar surface chemistry, crystallinity, specific surface area, and interfacial adhesion between biochar and the polymer. In addition, biocompatibility and cell culture results demonstrated that the BC500/UHMWPE composite exhibited better cell viability and proliferation of mouse (3T3) fibroblasts. The present results suggest that the biochar/UHMWPE composites have the potential to be used as a new kind of material in orthopedic applications.