Effects of MoS2 microencapsulation on the tribological properties of a composite material in a water-lubricated condition.

The severe abrasion wear of water-lubricated stern bearings usually occurs in the low-speed, heavy-duty working conditions. Consequently, it is vitally important to improve the anti-friction and tribological properties of composite stern bearings. The compound molybdenum sulfide (MoS 2) is a priority additive for enhancing the tribological properties of composites. However, the water capillary effect in the defects in the MoS 2 crystal can easily lead to oxidation and failure of the lubrication properties of MoS 2. In order to eliminate the chemical oxidation of MoS 2 in a humid environment, MoS 2 was microcapsulated to improve the chemical stability of MoS 2 in a humid environment. In this reported work, urea formaldehyde (UF) microcapsules loaded with MoS 2 as the core material were synthesized using in-situ emulsion polymerization. The synthesized microcapsules were added to a high-density polyethylene (HDPE) matrix to prepare composites. The ZCuSn 10 Zn 2 bronze which widely utilized in as the water-lubricated bearing bushing in watercraft was chosen as counterparts material. The tribological properties of the composites modified with microcapsules were investigated using a CBZ-1 tribometer under different running conditions, and the surface morphology of the tested composites was analyzed by using a scanning electron microscope. The test results revealed that the tribological property of the composites filled with the MoS 2 -containing microcapsules was better than the composite that lacked the MoS 2 microcapsules. The composites containing the MoS 2 microcapsules exhibited lower sliding friction and a smoother surface morphology, which was the result of the protection provided by the microcapsule walls. The UF walls of microcapsules isolated the steam produced by water and fiction, which delayed the oxidation of the MoS 2 crystals. Upon fracturing of the walls of the microcapsules, the encapsulated molybdenum disulfide was released between the friction pairs, which reduced the friction coefficient and adhesion wear. This reported study also provided an experimental basis for structural design and performance enhancement of water-lubricated bearings. • The MoS 2 -comtaining microcapsule was prepared via double emulsion method (w/o/w). • The composite modified by MoS 2 microcapsule and the composite filled with MoS 2 were tested under different tested conditions. • The tribology performances of composite modified by MoS 2 microcapsule were superior to the composite filled with MoS 2. • The microcapsule shell relieves the oxidation of MoS 2 under water lubricated condition. [ABSTRACT FROM AUTHOR]