PDA-PGA synergy for adhesive lubrication in bearings

Water lubrication is environmentally benign and widely used in marine stern bearings, but its low viscosity and poor interfacial affinity limit effectiveness on inert polymers like UHMWPE. This study presents a mussel-inspired co-lubrication strategy by integrating polydopamine (PDA) and polyglutamic acid (PGA) into a composite suspension. The PDA–PGA system synergistically enhances interfacial adhesion and hydration lubrication, forming a stable, self-replenishing lubricating film. Tribological tests show a 19.7 % reduction in friction and 21.9 % reduction in UHMWPE wear compared to water. Surface analyses confirm nitrogen-rich film deposition and improved shear resistance. These improvements are attributed to amide bonding, hydrogen bonding, and hydration layer formation. This strategy offers an effective lubrication solution for high-load, submerged UHMWPE–metal systems such as water-lubricated marine bearings.