Tribological and Nanomechanical Properties of Unmodified and Crosslinked Ultra-High Molecular Weight Polyethylene for Total Joint Replacements

Abstract

Wear of ultra-high molecular weight polyethylene (UHMWPE) continues to be a major obstacle limiting the longevity of total joint replacements. Efforts to solve the wear problem in UHMWPE have resulted in numerous studies dealing with the microstructure, morphology, and mechanical properties of this polymer. However, the fundamental wear mechanisms at different material length scales in total joint replacements remain elusive. Consequently, a systematic investigation of the initial stage of the wear process was performed in this study in order to obtain insight into the origins of wear in UHMWPE at submicrometer scales. Sliding experiments were performed with both unmodified and crosslinked (by gamma radiation treatment) UHMWPE subjected to reciprocating sliding against Co-Cr alloy in a bath of bovine serum under ranges of mean contact pressure and sliding speed typical of knee joints. Nanoindentation and optical, scanning electron, and transmission electron microscopy were used to examine the effect of crosslinking on the nanomechanical properties, dominant wear mechanisms, and microstructure of UHMWPE. The fundamental wear micromechanisms of unmodified and crosslinked UHMWPE are interpreted in the context of coefficient of friction, wear factor, creep, adhesion force, and microstructure results.

Effect of nitrogen ion irradiation on the nano-tribological and surface mechanical properties of ultra-high molecular weight polyethylene

“…6b). This trend has been already observed in UHMWPE nanoindentation studies and attributed to the lesser constrained molecular movement at the near surface than at the bulk state [31]. -A wide scattering in E r and H values is observed at indentation depths lower than 5 μm.…”

“…Nano-tribological characterization is crucial to analyze the effect of SHI on UHMWPE because local wear and surface damage play a dominant role in the failure process of joint implants [31]. Wear damage at the nano-level (where the applied loads are very low) may be different to the forms of wear damage at large scale.…”

Nanoindentation study of interphases in epoxy/amine thermosetting systems modified with thermoplastics

“…For low load values and consequently low penetration depths, diamond tip only displaces molecular chains from the surface, which possess higher degree of mobility than bulk material chains. As diamond tip increases penetration depth, molecular movements and material rearrangements in the vicinity of the rigid tip are incrementally prevented by the chains of adjacent material [38]. The increase in stiffness with the depth of indentation or applied load showed a surface mechanical behavior significantly different from the bulk material.…”

Friction-Wear Properties of Nickel-Free Co–Cr–Mo Alloy in a Simulated Body Fluid

“…Therefore, the high wear resistance of the alloy is necessary for metal-on-metal type hip joints. Friction-wear tests for artificial joints are conducted between a ultra-high molecular weight polyethylene and a metal to evaluate, for example, the wear-resistant performance of a modified polyethylene, 6) an ion implanted metal 7) and a lubricant with protein. 8) However, friction-wear test between metal and metal under a quasi-biological environment was not performed according to the best knowledge of the authors.…”