Mechanical properties, tribological behavior, and biocompatibility of high-density polyethylene/carbon nanofibers nanocomposites

Abstract

Carbon nanofibers (CNFs) with silane coatings were used as the reinforcement to enhance the mechanical and tribological properties of high-density polyethylene (HDPE) at different loading levels (0.5 wt% and 3 wt%). To improve the interfacial bonding between the CNFs and HDPE matrix, two types of silane coating thicknesses, 2.8 nm and 46 nm, were applied onto oxidized CNFs. Mechanical properties of the HDPE/CNF nanocomposites including Young’s modulus, ultimate stress, strain at fracture, as well as work of fracture, were investigated through tensile testing. The wear tests were performed on a pin-on-disk tribometer under the bovine serum lubricated condition. The coefficient of friction of the materials in contact with steel balls was monitored over the duration of the wear test. The addition of CNFs not only decreased the coefficients of friction of the nanocomposites, but also reduced their wear rates. The thicker silane-treated CNFs were found to be more effective in reducing the coefficients of friction and elongating the strain of fracture compared with the pristine CNFs and thinner silane-treated ones. The biocompatibility of the nanocomposites against a mouse osteoblast precursor cell line was also evaluated. Among the several types of nanocomposites, the one reinforced with the thicker silane-treated CNFs (46 nm) at 0.5 wt% loading level yielded the highest strain at fracture, the best wear resistance with a wear rate reduction of nearly 57.9% compared to the neat HDPE, and good biocompatibility, making it a promising material for biomedical applications.