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Friction data from: Directional hydration lubrication underwater: Enabled by TA/PAAm submicron particles

Wang, Chaobao1; Xi, Yuyang1

Research facility: Shaanxi Provincial Qinchuangyuan High-level Talent Program
Published Nov 14, 2025 on Dryad. https://doi.org/10.5061/dryad.kwh70rzjd

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Abstract

Achieving durable hydration lubrication underwater is challenging due to interference from interfacial hydration layers. This study developed tannic acid/polyacrylamide (TA/PAAm) nanoparticles, synergistically combining TA's adhesive pyrogallol groups with PAAm's hydrophilic chains to enhance aqueous lubrication. Tests showed TA/PAAm suspensions improved copper/ultra-high molecular weight polyethylene tribo-pair wettability by 42% (contact angle reduction), lowered friction coefficients by 29%, and reduced wear volume by 56% versus water. Mechanistically, TA immobilizes nanoparticles onto surfaces via catechol-mediated adhesion to form a protective film, whereas PAAm disrupts the hydration layer via its hydrophilicity, establishing a hydrogen-bonded lubrication network and thereby enhancing lubrication performance. This strategy provides an environmentally friendly directional lubrication solution for marine applications such as water-lubricated bearings and subsea mechanical seals.