ON SLIDING FRICTION AND WEAR OF PEEK AND ITS COMPOSITES

The friction and wear behaviour of different molecular weight virgin p oly(ether ether)ketones (PEEK) and of PEEK blends with polytetrafluoro ethylene (PTFE), as well as of PEEK composites with short carbon fibre s was studied under dry sliding conditions against hard steel on a pin -on-disc apparatus. As characterised by the melt viscosity, and simila r crystallinities after heat treatment, the high molecular weight PEEK had a better wear resistance than low molecular weight PEEK. The effe cts were greatest when the pv-level was high. Opposite to the wear rat e, the coefficient of friction was not clearly affected by the pv comb ination term. The spherulite size and hardness of the PEEK play an imp ortant role in both friction and wear performance. Concerning the fric tion and wear properties of PEEK-PTFE blends, the inclusion of PTFE re duced the friction of PEEK. The lowest friction coefficient was measur ed for the blend with a PTFE volume fraction of 15%. The wear rates of the blends with PTFE volume fraction varying from 5-85% were lower th an that of virgin PEEK. A minimum value in wear rate existed at a PTFE volume fraction of 5%. Wear of the PEEK-composites was always lower t han for the neat PEEK matrix, but was increased with increasing temper ature. For minimum friction coefficient there was an optimum content o f fibres at about 10 vol.%.