Investigation of ultra-low friction and high wear resistance on single Al2O3 fiber surface with WS2-modified coconut oil/WPU sizing agent

Abstract

A green sizing agent of modified tungsten disulfide-modified coconut oil/waterborne polyurethane (WP-MCO/WPU) was innovatively prepared for improving the tribological properties of single Al₂O₃ fiber (single AF). This sizing agent formed by WS₂-PEG as an emulsifier with MCO and WPU showed good viscosity stability, wettability, thermal and dispersion stability. Subsequently, the effects of CO, MCO and WS₂-PEG concentrations on the tribological properties of fibers were investigated. When the sizing agent contained 15 wt% of MCO-3 (esterification ratio: 5:1), the coefficient of friction (COF) was reduced from 0.2 (CO/WPU@single AF) to 0.121 (MCO-3/WPU@single AF), and a lubricant oil film was generated on the friction surface, the anti-friction was improved. However, with the increase of friction frequency and normal load, the oil film of MCO-3/WPU@single AF was destroyed and the anti-wear performance deteriorated. The sizing agent containing WS₂-PEG (WP-MCO-3/WPU@single AF) had better anti-friction and superior anti-wear performance than without WS₂-PEG (MCO-3/WPU@single AF). The COF was reduced from 0.121 to an ultra-low value of 0.056, and a dense lubricating film was exhibited of WP-MCO-3/WPU@single AF under high-frequency, high-load friction conditions. From mechanism analysis, the improved lubrication performance was attributed to the polarity and boundary lubrication of MCO, the unique load-bearing structure and friction-reducing of WS₂-PEG. In conclusion, this sizing agent had attractive prospect in improving the wear resistance of ceramic fibers.