Influence of grinding energy in morphology and tribological performance of self-lubricating polymeric blends PAEK + PTFE.

Improving the energy efficiency of mechanical systems and reducing the usage of lubricant oils and related additives are challenging tasks of the 21st century. Consequently, the application of tribopolymers increases due to their easy processing (injection moulding) and lower density (mass reduction). Among them are the poly(ether-ether-ketone) (PEEK) and the poly(aryl-ether-ketone) (PAEK) with outstanding mechanical properties, and poly(tetrafluorethylene) (PTFE), a solid lubricant. This work produced powder-like PAEK + PTFE blends (2%–30% PTFE) by low and high-energy grinding processes; then, the specimens were shaped by hot pressing. The morphology and composition of the post-grinding particles were analysed by white light interferometry (WLI), scanning electron microscopy (SEM) and X-ray dispersive energy spectroscopy (EDS). The fractography and thermal analysis of the specimens were performed via SEM-EDS and differential scanning calorimetry (DSC). For tribological evaluation, reciprocating (2Hz, 10 mm) cylinder-on-flat tests were conducted to determine the lubricious regime duration, the friction coefficient (COF) during the steady-state regime, and wear rates, where the worn volumes (specimen and counterbody) were measured by WLI. High-energy grinding leads to smaller and more plastically deformed particles. In addition, the incorporation of PTFE into PAEK is more homogeneous with a higher crystalline degree. The self-lubricating effect is manifested from 5% of PTFE, and the best results are reached for 15% of solid lubricant, with an average wear rate of 9.4 × 10−16 mᶟ/Nm and COF of 0.08, against 5.3 × 10−14 mᶟ/nm and 0.32 for pure PAEK, respectively. • The two mixing methods used to produce the blend (PAEK + PTFE) resulted in completely different blends structural morphology. • But high energy method induces the formation of polymers with higher crystallinity degrees. • Higher tribological performance was reached from 5% of PTFE concentration. [ABSTRACT FROM AUTHOR]