Ultralow friction polymer composites enabled by the solid–liquid core microcapsules at high temperatures

The application of oil-containing microcapsules for lubrication at high temperatures has been a great challenge due to the volatilization and viscosity reduction of the oil. In this study, thermostable SiO2 was selected as the shell and WS2 silicone oil dispersion as core to prepare heat-resisting solid–liquid compound microcapsules. The tribological properties of the composites at high temperatures were evaluated, and the lubrication mechanism of the solid–liquid coupled microcapsules was investigated. The results showed that the microcapsule composites were able to maintain low friction coefficient (COF) and wear rates at high temperatures (COF of 0.098, 73 % lower than pure epoxy, and wear rate of 4.87 × 10-6 mm3/N·m, two order of magnitude lower than pure epoxy, at 300 ℃), and in addition, the compressive strength of the composites was improved due to the excellent mechanical properties of SiO2. The strategy proposed in this study is expected to be a general solution and can be extended to other polymer composites with excellent high-temperature lubrication properties by incorporating microcapsules with different solid–liquid core in the matrix.