Preparation and tribological properties of solid-liquid synergetic self-lubricating PTFE/SiO2/PAO6 composites

Herein, 25 kinds of polytetrafluoroethylene (PTFE) composites with solid-liquid synergetic self-lubricating property were prepared by filling PTFE matrix with hollow SiO2 particles and lubricating oil (PAO6). Hollow SiO2 particles containing PAO6 acting as lubricating fillers were applied to enhance the tribological performances of PTFE matrix. The generated PTFE composites displayed solid-liquid synergetic self-lubricating property and could achieve ultralow friction. Factors such as the cold-pressed pressure and the SiO2 content that affect the tribological performance of the composites were investigated in detail. The compactness of the composites was enhanced when the cold-pressed pressure increased. The porosity of the composite with 25 wt% SiO2 decreased from 38.2% to 14.3% when the cold-pressed pressure was increased from 10 MPa to 50 MPa. As the cold-pressed pressure was increased, the antiwear performance of the composites was enhanced but their antifriction performance become worse. The composites containing PAO6 achieved lower coefficient of friction (COF) and smaller wear rates than composites without PAO6. The COF value decreased from 0.143 (pure PTFE) to an ultralow value of 0.037 (composite 5%-10 MPa-oil). The enhanced antifriction performance of the composite was associated with the synergistic lubricating effect of the liquid lubricant of PAO6 and the lubrication of the PTFE matrix. All the prepared PTFE/SiO2/PAO6 composites exhibited excellent antifriction performance and improved antiwear property and thus can be used to fabricate a new kind of self-lubricating materials.