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

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.