Two-dimensional clay nanosheet-reinforced polytetrafluoroethylene composites and their mechanical/tribological studies

Polytetrafluoroethylene (PTFE) polymer is used extensively in industry as a solid lubricant because of its lack of reactivity with most industrial materials. However, PTFE has a low abrasive resistance, limiting its application. In this study, the mechanical and tribological characteristics of PTFE-based composites with the addition of clay nano-sheets (CNSs) were investigated. Clay nano-sheet-PTFE composites (CNSTCs) containing 1, 3, and 5 wt. % of CNSs were prepared by employing a compression moulding method. To investigate the tribological characteristics and wear mechanism of CNSTCs, a pin-on-ring test, scanning electron microscopy (SEM), and optical microscopy (OM) were employed. The results indicate that adding CNSs decreased the friction coefficient substantially. Additionally, the wear rates decreased from 1.09 ×10^-3 mm³/(Nm) in the pure PTFE sample to 0.32×10^-5 mm³/(Nm) for the 5 wt. % CNSs filled composite. This shows that the wear rate of the PTFE-based composite is reduced by up to 340 times with the addition of 5 wt. % CNSs. SEM and OM observations revealed that CNSs could inhibit the growth of microcracks in CNSTCs and change the wear mechanism from adhesive to abrasive. Furthermore, adding CNSs resulted in a more uniform and thinner transition film formation, with reduced secondary wear and friction. The effects of the size, percentage, and type of embedded fillers were compared with previous studies. The analysis revealed that in addition to competitive cost and high availability, CNSs have superior characteristics and can be employed to enhance the tribological properties of PTFE nanocomposites.