Tribological behavior of polymer composites functionalized with various microcapsule core materials

Abstract Severe abrasion wear of water-lubricated bearings usually occurs during low-speed and heavy-duty working conditions. It is vital to improve the anti-friction and tribological properties of the composites used in the water-lubricated bearings. In this reported work, polymer microcapsules were added to matrix material as compositional modifications, to improve the tribological properties of the bearing as it was worn against a cast copper bushing. These microcapsules appeared to reduce the phase splitting between the low-melting-point lubricant and the matrix. In this particular study, urea formaldehyde (UF) microcapsules loaded with two lubricants included N, N′-ethylene Bis-stearamide and Erucic Amide as core materials were synthesized by double emulsion method (w/o/w) and then blended with high-density polyethylene (HDPE) to form the composites. The tribological properties of the microcapsule-modified composites were investigated using a CBZ-1 tribometer under different running conditions. After testing, the microcapsules were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and the surface morphologies of composites were analyzed by using Scanning Electron Microscopy (SEM). The analytical results revealed that the tribological properties of the composites were improved as the quantity of microcapsules in the composite was increased. The composites containing the microcapsules produced lower sliding friction and exhibited a smoother surface morphology, which was due to the lubrication provided by the Erucic Amide in the microcapsules. As shell of microcapsules was worn away during the test, the encapsulated Erucic Amide was released into the friction pairs, which established a dense lubrication film. When the mass fraction of the Erucic Amide containing microcapsules is 10 wt%, the frictional coefficient of composites is reduced by 66.9% under low sliding velocity and middling applied load conditions. This study also provided an experimental basis for the structural design and performance enhancement of water-lubricated bearings.