Nanoscale Characterization of Wear Particles Produced From CNF-Reinforced HDPE Composites

Wear debris of materials used nowadays in orthopedic replacements is known to be the major cause of failures in a long-term period. Recent studies showed that the autoimmune reaction to the foreign body is not only the consequence of the material itself, but also depends on the size and shape of the wear particles. In this paper, carbon nanofiber (CNF) reinforced high density polyethylene (HDPE) debris particles were characterized both quantitatively and morphologically. Various weight concentrations (0.5 wt.%, 1 wt.% and 3 wt.%) and silane coating thicknesses (2.8 nm and 46nm) of CNFs in the nanocomposites were investigated. Wear tests were provided by a pin-on-disk tribometer with phosphate buffered saline as the lubricant. The wear debris was collected, isolated and characterized by scanning electron microscopy (SEM) at high magnifications and also by dynamic light scattering (DLS) particle sizing. The DLS measurements were in general consistent with the SEM observations. Small sphere-shaped wear particles of various diameters (predominantly less than 100 nm) were observed on the SEM images for all materials. The particles’ diameter distributions obtained by the DLS technique also showed that the mean diameters of the majority of the particles were mostly less than 100 nm. No correlation was found between the morphology, as well as the size distributions, of the debris particles and CNF concentrations or silane coating thickness in these experiments.