Using mixture design experiments combined with a multi-objective optimization method to prepare high-strength, low-friction m-polyphthalazine ether sulfone ketone water-lubricated composites

To address the utilization needs of composites under unconventional lubrication conditions, this paper conducted a mixture design experiment utilizing m-polyphthalazine ether sulfone ketone (m-PPESK) as the resin matrix, along with short-cut carbon fibers (SCF), polytetrafluoroethylene (PTFE), and graphite (Gr) as modified fillers. The mathematical models between each response value (including compressive strength, tensile strength (TS), coefficient of friction under dry friction and water lubrication conditions [μ_dry and μ_water]) and filler contents were constructed. The impact of fillers and their synergistic interactions on the properties of composites was systematically studied. Combined with the multi-objective optimization method, the optimal formula of m-PPESK composite was determined as 70 wt% resin, 9 wt% SCF, 10 wt% PTFE, and 11 wt% Gr. Compared to the pure resin, the optimized composites demonstrated a 25.4% increase in TS, alongside a 56.4% and 55.9% reduction in μ_dry and μ_water, respectively. Scanning electron microscopy and energy dispersive spectroscopy analyses indicated that the multicomponent fillers could synergistically facilitate the formation of a friction transfer film, thus improving the tribological properties of composites. Highlights: High-strength, low-friction m-PPESK water-lubricated composites were prepared. The tensile strength of composites was increased by 25.4%. The μ_dry and μ_water of composites were reduced by 56.4% and 55.9%. The regression equations obtained by mixture design had good predictability. SCF, PTFE, and Gr had synergistic effects on the tribological properties.