Investigations on Performance Properties of Nano-Micro Composites Based on Polyetherketone, Short Carbon Fibers and Hexa-Boron Nitride

Mechanical, thermal and tribological performance properties of poly-ether-ketone (PEK) are superior to those of poly-ether-ether ketone (PEEK) at elevated temperatures. Hexa boron nitride (hBN) is an excellent solid lubricant especially because of its high temperature stability. A series of eight composites based on PEK and short carbon fibers (CF) as reinforcement were developed using variable sizes of hBN as a solid lubricant to study the influence of size on improvement in tribo-properties of the composites. It was observed that the developed series of CF reinforced PEK composites led to very good tribo-performance (specific wear rate (K ₀) in the range of 10^–16 m³/Nm and coefficient of friction (μ) in the range of 0.05–0.07 under high operating PV values 32–36 MPa m/s). The inclusion of hBN led to significant reduction (∼50%) in μ at higher loads only at the cost of slight deterioration in wear resistance (W_R ). However, during long duration tests most of the composites, including that with nano-hBN, showed higher wear resistance and lower μ than that without hBN. Amongst the various sizes of selected particles of hBN, 0.5 μm size proved to be the most promising for achieving lowest μ. Based on worn surface analysis, it was concluded that the excessive breakage of fibers was the main reason for increased wear. As evident from SEM analysis of worn surfaces, it was primarily due to deterioration in fiber-matrix bonding due to hBN which is an inert (low surface energy) filler.