High-load self-lubricating EP/PTFE composites via stress-triggered solid-liquid core MoS2/PAO6@UF microcapsules

Stress-triggered MoS 2 /PAO6@UF microcapsules enabled high-load PTFE/epoxy liners with stable lubrication under step-loading up to 7.5 kN. • MoS₂ fraction tuned friction–wear performance, achieving 0.056 COF and 6.4 × 10 -8 wear rate. • A dynamic lubrication interface consisting of PAO6 oil film, MoS 2 solid film, and PTFE transfer film was revealed. Self-lubricating spherical plain bearings are key components in aircraft flight-control systems, and their moldable liners must provide stable lubrication under high-load conditions. However, it remains challenging to achieve low friction, low wear, and durable transfer-film protection in epoxy-based self-lubricating liner materials. In this study, Stress-triggered solid–liquid microcapsules consisting of a polyalphaolefin (PAO6)/MoS₂ lubricant core and a urea–formaldehyde (UF) shell were fabricated by in situ polymerization and subsequently incorporated with polytetrafluoroethylene (PTFE) into an epoxy matrix to prepare self-lubricating liner composites. The resulting microcapsules were denoted as MoS₂/PAO6@UF microcapsules. The microcapsules showed spherical morphologies, an average particle size of 6–7 μm, and good thermal stability below 200 °C. Under 1500   N and 100   rpm, the composite containing 5   wt.% MoS 2 in the microcapsule core exhibited the lowest coefficient of friction of 0.056, whereas the composite containing 10   wt.% MoS 2 achieved the lowest wear rate of 6.4 × 10 -8 mm 3 /(N·m). Step-loading tests showed that the composites maintained effective lubrication up to 6.5–7.5 kN, indicating good high-load-bearing capability. Optical microscopy, FTIR, XPS, and Raman analyses confirmed the formation of a composite lubricating interface composed of released PAO6, a PTFE transfer film, and a MoS 2 solid lubricating film. The PAO6 oil film reduced interfacial shear, the PTFE transfer film stabilized the lubricating interface, and the MoS 2 solid lubricating film provided load-bearing support. These results establish a stress-triggered, three-component lubrication strategy for high-load, moldable epoxy liners.