Solid-liquid coupled self-lubricating microcapsules with a wide temperature range: tribological applications in polymer composites

In this study, hybrid boron nitride-nano silica solid self-lubricating filler (hBN-SiO₂) was prepared via in-situ growth method. Using lubricating oil containing hBN-SiO₂ as the core material and polyimide (PI) as the wall material, solid-liquid coupled self-lubricating microcapsules (OIL/hBN-SiO₂@PI) were fabricated. These capsules exhibit high core content (OIL content: 56 wt%) and excellent thermal stability (mass loss of only 9.8 wt% after constant temperature at 310 °C for 3 h). These microcapsules can notably improve the tribological performance of Polyphthalazinone Ether Ketone (PPEK). Specifically, for the PPEK-OIL/hBN-SiO₂@PI composite, the wear rate (ω = 1.70 × 10⁻¹⁵ m³/(N·m)) and friction coefficient (µ = 0.089) are reduced by 91.5% and 86.0% respectively. The interfacial friction region develops a stable transfer film owing to a distinctive “solid-liquid synergistic” lubrication mechanism. This work provides new insights for designing high-temperature-resistant solid-liquid coupled capsules and developing self-lubricating polymer composites.