A Self-Lubricating PEEK Composite Enhanced by Microcapsules via Friction-Triggered Hydrogel Layer Formation

A hydrogel is an ideal material for lubrication, with hydrogel-filled microcapsules emerging as a promising strategy to simultaneously achieve low friction and high load-bearing capacity. The hydrogel microcapsules were prepared with porous SiO2 as the shell; polyvinyl alcohol (PVA), polyacrylic acid (PAA), tannic acid (TA), and dimyristoyl phosphatidylcholine (DMPC) sol (named as PPTD sol) as one type of core material, and calcium lactate as another core material, and the two kinds of microcapsules were compounded into the PEEK matrix. During friction, the released PPTD sol and calcium lactate were cross-linked into the hydrogel through microporous extrusion and covered on the friction surface. The in situ formation of the lubricating hydrogel layer significantly improved the polymer's lubrication performance under severe operating conditions, with the friction coefficient decreased by above 82% and the one-order-of-magnitude decrease of the wear rate. The strategy is expected to become a universal solution.