Structural evolution of ultrahigh molecular weight polyethylene under sliding friction in seawater

Ultrahigh molecular weight polyethylene (UHMWPE) is suitable for tribological applications in various environments because of its advantageous characteristics, including its high-impact strength, excellent resistance against wear and corrosion, and self-lubricating properties. However, the tribological behavior of UHMWPE under seawater lubrication is still poorly understood. In this study, the wear mechanisms of UHMWPE in seawater environment were elucidated by examining its morphology and structural evolution during sliding friction. The tribological properties of UHMWPE were significantly affected by the sliding speed in seawater. At low sliding speeds, no long-strip structures were observed on the worn UHMWPE surface. However, as the sliding speed was increased, prominent convex long-strip structures appeared and became more densely distributed with time. The molecular chains in the amorphous region of UHMWPE stretched along the sliding direction under stress. In the crystalline region, molecular orientation, and lamellar slip were accompanied by molecular conformational transformations. During the initial stage of sliding friction, UHMWPE mainly exhibited adhesive wear caused by plastic deformation. Subsequently, the wear mechanism of UHMWPE gradually changed from adhesive wear to a combination of adhesive and abrasive wear, and its wear intensified over time.