Preparation of monodisperse cellulose acetate-laurate/calcium borate/cellulose acetate-laurate nanocapsule and its tribological properties in polyalphaolefin oil

Two-dimensional composites with a core-shell structure used as lubricant additives tend to experience separation and delamination of the core and shell materials under high loads, resulting in poor tribological performance. Herein, monodisperse and spherical cellulose acetate-laurate/calcium borate/cellulose acetate-laurate (CAL/CB/CAL) nanocapsules with three-dimensional network structure were prepared by high-pressure homogenization combined with solvent evaporation method. CAL/CB/CAL exhibited good dispersibility and long-term dispersion stability in polyalphaolefin (PAO) oil, and only slight stratification appeared after 21 d. Moreover, CAL/CB/CAL used as a lubricant additive for PAO oil demonstrated excellent anti-wear and extreme pressure properties under 392 N at 75 °C. Particularly, the wear scar diameter and coefficient of friction of CAL/CB/CAL were reduced by 14.1 and 26.4 % under 490 N, respectively, relative to CB@CAL with a core-shell structure. The excellent tribological properties of CAL/CB/CAL under low load were attributed to the synergistic action between the rolling effect of CB and the sliding effect of CAL, while under high load, its three-dimensional network structure could avoid the separation and delamination of CB and CAL, thus evenly penetrating into the friction surface to form tribochemical films. This study provides feasible approach to address the limitations of two-dimensional core-shell composites in lubrication applications.