Cui Wen, Bian Yanyan, Zeng Hongkai, Zhang Xiaogang, Zhang Yali, Weng Xisheng, Xin Shixuan, Jin Zhongmin
Tribology Research Institute, School of Mechanical Engineering, Southwest Jiaotong University, Chengdu, 610031, China.
Department of Orthopedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100730, China.
J Mech Behav Biomed Mater. 2020 Apr;104:103629. doi: 10.1016/j.jmbbm.2020.103629. Epub 2020 Jan 10.
Ultra-low-wear polyethylene (ULWPE) is a new metallocene catalyzed high density polyethylene (HDPE)material. Previous studies have demonstrated that it has excellent biocompatibility and wear resistance, whereupon indicating great potential in the applications to artificial joints. However, as a newly developed material, its tribological behavior and wear resistance mechanism has not been well understood. In the current study, we experimentally evaluated the tribological behavior of ULWPE, and investigated its high wear resistance mechanism in terms of microstructure, crystallization properties, mechanical, physical, and chemical properties. ULWPE manifested the best tribological performance on pin-on-disc (POD) wear tests compared with the most widely used artificial joints materials, with a wear volume of 0.720 ± 0.032 mm/million cycles (Mc) and 0.600 ± 0.027 mm/Mc against cobalt-chromium (CoCr) alloy disc and zirconia toughened alumina (ZTA) ceramic disc, respectively. The results of the wear morphology analysis showed that the surface of ULWPE was the slightest, with no obvious surface damage, debris shedding and wear pits. We reveal that three major factors mainly contributed to its high wear resistance. First, ULWPE demonstrated a high crystallinity and a compact crystalline morphology comprised of long linear molecular chains, which contributed to its good mechanical performance. As confirmed by the mechanical test, ULWPE had a very high density, hardness, and tensile elongation at break. The high hardness and strength laid a solid foundation to a low wear volume, and its high ductility and hardness helped to endure abrasive and adhesive wear, resulting in excellent wear resistance. Second, the results of wettability analysis showed that the contact angle formed on the surface of ULWPE was the lowest and the surface energy was the highest. The hydrophilicity of ULWPE provided good lubrication conditions in body fluid. Third, it also had a lower oxidation index. The high hardness, high strength, high ductility and good wetting of ULWPE materials reduced the damage of the material to adhesion and abrasive wear, resulting in excellent wear resistance.
超低磨损聚乙烯（ULWPE）是一种新型的茂金属催化高密度聚乙烯（HDPE）材料。先前的研究表明，它具有优异的生物相容性和耐磨性，因此在人工关节应用中显示出巨大潜力。然而，作为一种新开发的材料，其摩擦学行为和耐磨机理尚未得到很好的理解。在当前的研究中，我们通过实验评估了ULWPE的摩擦学行为，并从微观结构、结晶性能、机械、物理和化学性能方面研究了其高耐磨机理。与最广泛使用的人工关节材料相比，ULWPE在销盘（POD）磨损试验中表现出最佳的摩擦学性能，与钴铬（CoCr）合金盘和氧化锆增韧氧化铝（ZTA）陶瓷盘的磨损体积分别为0.720±0.032 mm/百万次循环（Mc）和0.600±0.027 mm/Mc。磨损形态分析结果表明，ULWPE的表面损伤最小，没有明显的表面损伤、碎屑脱落和磨损坑。我们发现三个主要因素促成了其高耐磨性。首先，ULWPE表现出高结晶度和由长线性分子链组成的致密结晶形态，这有助于其良好的机械性能。经力学测试证实，ULWPE具有非常高的密度、硬度和断裂伸长率。高硬度和强度为低磨损体积奠定了坚实基础，其高延展性和硬度有助于承受磨料磨损和粘着磨损，从而具有优异的耐磨性。其次，润湿性分析结果表明，ULWPE表面形成的接触角最低且表面能最高。ULWPE的亲水性在体液中提供了良好的润滑条件。第三，它还具有较低的氧化指数。ULWPE材料的高硬度、高强度、高延展性和良好的润湿性减少了材料对粘着磨损和磨料磨损的损伤，从而具有优异的耐磨性。
