Exploration of potential of solid lubricants and short fibers in Polyetherketone (PEK) composites

Polyetherketone (PEK) is one of the least explored specialty thermoplastic polymers for its tribo-utility. It exhibits continuous operating temperature up to 280 °C and under short-term loads it can function up to 350 °C. In literature, hardly anything is reported on the adhesive wear performance of PEK and its composites. Three composites based on PEK containing short fibers of carbon/glass along with various solid lubricants were developed and characterized for thermal and mechanical properties. The tribo-properties were studied under varying loads and speeds by sliding a composites pin against a mild steel disc as a counter face. The studies were focused to examine the role of these ingredients on enhancing pressure × velocity limit (PVlimit), which is an indication of utility of a tribo-polymer in severe operating conditions. The performance assessment was done according to multiple parameters; such as magnitude of coefficient of friction (μ) and its fluctuations with time, PVlimit, compatibility with the counter-face, specific wear rate (K0), etc. Very low K0 (≈10−16 m3/Nm), very low μ (0.04–0.20) and very high PVlimit values (>95.2 MPa m/s) were reported for these composites. White graphite (hexa boron nitride—hBN) proved to be the most efficient solid lubricant. The wear mechanisms using scanning electron microscopy of worn surfaces of pins and discs were studied. It was interesting to observe that glass fibers in the composite showed extremely good performance instead of showing abrasion and high μ. A very different friction and wear mechanism was claimed to be responsible for this. A synergism between lubricating action of two lubricants and layer of molten glass on the disc was the main reason for the enhanced performance.