Influence of Five-Year Degradation on Mechanical and Tribology Properties of Ultra-High-Molecular-Weight Polyethylene

Ultra-high-molecular-weight polyethylene (UHMWPE) has been the most commonly used bearing material in total joint replacement. The degradation of UHMWPE components has a notable influence on its mechanical properties. UHMWPE samples were immersed in simulated fluid (SBF) up to 5 years and the change in chemical composition and mechanical and wetting properties was investigated. It was found that the oxygen/carbon (O/C) ratio and crystallinity increased from 14.5 and 50.0% before immersion to 52.8 and 60.7% after immersion in SBF for 5 years, respectively. These resulted in a reduction in ball indentation hardness, scratch coefficient, peak load, and contact angle by 35.7, 21.0, 15.8, and 14.0%, respectively, after 5 years of immersion. The steady-state friction coefficient and wear rate increased 83.3 and 43.8%, respectively, after immersion in SBF for 5 years. The preliminary study indicated that the scratch test was an effective method to evaluate the surface performance of UHMWPE after short-term degradation, and small punch test was often used to assess the bulk properties of UHMWPE after long-term degradation.