Tensile and tribological behaviors of PEEK/nano-SiO2 composites compounded using a ball milling technique

In this work, nano-SiO2 particles filled polyetheretherketone (PEEK), with nano-SiO2 contents ranging from 0.5 to 4 vol.%, were compounded by a ball milling process performed under room temperature. Nanocomposites were prepared through compression molding as-milled PEEK/nano-SiO2 mixtures without further melt mixing. Differential Scanning Calorimetry (DSC) thermograms indicate that the ball milling process can impose a non-equilibrium order in PEEK due to its repetitive deformation. The incorporation of nano-SiO2 leads to a significant improvement in material stiffness and a decrease in material ductility. Fractography analyses suggest that secondary cracks initiating from the nanoparticles as a result of stress concentration are responsible for the parabolic markings and dimples observed in the fracture initiation regions of the nanocomposites with different nano-filler contents. The wear resistance of PEEK is significantly improved after incorporating nano-SiO2 and at a rather low nano-SiO2 loading, i.e. 1 vol.%, the composite presents the optimum wear resistance.