Tribological performances and self-lubricating mechanism of monomer casting nylon-6 composite coatings containing lube base oil-loaded microcapsules

The tribological properties of monomer casting nylon-6 (MC PA6) play an important role in ensuring energy consumption, component integrity and reliability in construction machinery. In this work, MC PA6 coatings containing different amount of lube base oil-loaded poly(urea-formaldehyde) microcapsules are prepared, and the tribological properties of the composite coatings are investigated. Compared with the pure coating, the friction coefficient and specific wear rate of the composite coating containing 20 wt% of oil-loaded microcapsules are 0.16 and 0.47 × 10 −5 mm 3 /Nm, which correspond to decreases of 56.7% and 91.8% respectively. Moreover, by introducing the oil-loaded microcapsules, the heat produced during friction is greatly reduced and the friction temperature of all composite coatings (~40–50 °C) decreases more than 40 °C, as compared with that of pure coating (93.7 °C). Self-lubricating mechanism is investigated through microscopy and EDS analysis, which indicate that the improvement of tribological properties is attributed to the formation of uniform, continuous and thin lubricating film on the worn surface. This study would provide significant guidance for the design and preparation of MC PA6 composite coatings with high self-lubricating properties. • Lube base oil-loaded PUF microcapsules are introduced into MC PA6 coatings. • The composite coatings show remarkable improvement on tribological properties. • Lowest friction coefficient and specific wear rate are 0.14 and 0.47 × 10 −5 mm 3 /Nm. • Friction temperature of the composite coatings is significantly reduced. • The self-lubricating mechanism is systematically discussed.