Enhancing Water-Lubricated Tribological Performance of Ultra-High Molecular Weight Polyethylene via Zwitterion Blending

This study developed an interface-functionalized ultra-high-molecular-weight polyethylene (UHMWPE) by incorporating a strongly hydratable zwitterion, sulfobetaine methacryloxyethyl (SBMA), to enhance its wear resistance under synovial fluid lubrication. Composite materials with SBMA gradients (0–7.5 wt%) were prepared via melt blending. Pin-on-disc tribological tests demonstrated that at 7.5 wt% SBMA loading, the friction coefficient decreased by 37% under an 8 N load, while the volumetric wear rate reduced by 49% at a 30 N load. Multiscale characterization revealed dual synergistic mechanisms: (1) interfacial hydration reinforcement - the sulfonate group in SBMA formed hydrogen-bonded hydration layers, decreasing the contact angle from 69° to 56° and suppressing wear through hydration lubrication; and (2) structural influence - SBMA prevents crystallization by acting as a plasticizer. But as concentration rises, SBMA aggregates, reducing the plasticizing impact and enhancing mechanical qualities. This study provides a novel strategy that combine superior hydration effect to enhance tribological performance of UHMWPE.