Effect of different loads on wear mechanisms of polyether-ether-ketone in normal saline and debris-isolating method

Abstract

Polyether-ether-ketone (PEEK) has been proposed as a biocompatible artificial joint material. Wear particles, generated by friction between artificial joints, lead to bone resorption, aseptic loosening, and ultimately, joint failure. The size and morphology of wear particles contain information of friction and wear. Aim to obtain the wear mechanism of PEEK under different loads, this study separated PEEK debris and investigated the mechanism of wear debris and the relationship between wear mechanism and PEEK-debris morphology. An experiment was carried out with a pin-on-plate testing apparatus under different load conditions, with PEEK sliding against XLPE under saline lubrication. A method of isolating PEEK and XLPE debris from 0.9% normal saline at the same time was investigated by low-speed centrifugation. The morphologies of worn surface and wear debris were obtained based on scanning electron microscopy. The results showed that the maximum friction coefficient and minimum wear loss were 0.115 and 0.223 mg at the load of 50 N. The friction coefficient decreased and the wear loss increased with the load increase. This debris-isolation method can effectively isolate PEEK and XLPE particles larger than 200 nm in diameter. More than 96% wear PEEK particles range from 0.1 µm to 10 μm. Compared with the debris generated under the lower load condition, 0.8% more large wear particles with irregular shapes were found at a load of 150 N. The morphology of wear particles is consistent with the wear mechanism.

Evaluation of the tribological properties of two PEEKs sliding against Al2O3, WC and DLC coatings under dry friction and water lubrication

“…Figure 9 indicates that the friction coefficient increases with an decrease in speed and load [37]. The hydrodynamic effect formed by the tribopairs is stronger when speed increases, forming a thicker water film and reducing the friction coefficient [38].…”