Ultra-high-molecular-weight polyethylene (UHMWPE) is widely used in water-lubricated bearings and other marine sliding components because of its low friction, wear resistance, and corrosion resistance. However, long-term sliding can cause plastic deformation and wear. Lipid organic matter in real seawater may enter the contact interface and affect liquid diffusion and molecular chain motion. Its influence on the wear and modification of UHMWPE remains insufficiently understood.
In this study, squalene was selected as a representative lipid component. Molecular dynamics simulations and tribological experiments were combined to investigate the effects of surface annealing and irradiation crosslinking on UHMWPE. The simulation models included Fe plate constrained annealing and different crosslinking degrees. Experimentally, UHMWPE was annealed at 110 °C for 1 h under a 304 stainless steel plate and gamma irradiated at 100 kGy. Wear behavior, local mechanical response, and microstructural evolution were evaluated using tribological tests, FTIR, and XRD.
The simulations showed that constrained annealing formed a dense surface layer that reduced water and squalene penetration and limited shear deformation within UHMWPE. Crosslinking provided network constraints throughout the material and restricted chain sliding, stretching, and orientational rearrangement. Experiments showed that both treatments slightly increased the coefficient of friction but markedly reduced wear. In the 50 wt% seawater-squalene mixture, annealing and irradiation crosslinking reduced wear volume by 0.13~0.26 and 0.20~0.33 mm³, respectively. Both treatments also increased scratch resistance and suppressed squalene penetration and friction-induced structural changes. Irradiation crosslinking provided greater improvement because its network constraints acted throughout the material, whereas annealing mainly relied on surface densification. These findings support the modification of UHMWPE components used in marine equipment under complex seawater conditions.

modified UHMWPE,wear mechanism,seawater,squalene,molecular dynamics simulation