Polydopamine-modified polysulfone/silica double-walled heat-resistant microcapsules efficiently improve the tribological properties of polyamides

The tribological properties of nylon 6 (PA6) play an important role in regulating the energy consumption, component integrity, and reliability of construction machinery. In order to improve the tribological properties of polyamide, by using high temperature resistant green lubricant ionic liquid (IL) lubricant as core material and polysulfone (PSF) and SiO2 hybrid system as wall materials, double-walled IL@PSF/SiO2 self-lubricating microcapsules with high core content has been prepared. By exploring different emulsifiers and different agitation rates, the degree of encapsulation of an ionic liquid (IL) has been improved and the optimal synthesis conditions for microcapsules have been determined. And the core content was as high as 68 wt% The introduction of SiO2 in the wall material increased the thermal softening temperature of the microcapsules up to 400 °C. The friction coefficient and specific wear loss of a PA6 composite containing 10 wt% IL-loaded microcapsules were reduced by 82% and 87.9% comparing with pure PA6, respectively. The self-lubrication mechanism has been investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and atomic force microscope (AFM), and the results showed the formation of a uniform, continuous, and thin boundary lubricating film on the wear surface to be the main reason for the improved tribological performance.