The friction and wear of polymers in non-conformal contacts

The behaviour of a number of polymers and polymeric composites in non-conformal contact is discussed. It is shown that friction-generated heat has a major influence on the materials' performance and that, for example, the use of acetal in spur gears is controlled by the temperature rise. The wear behaviour of the materials examined showed a wide variation and in all cases was totally different from that found in conventional pin-on-disc tests. Of the materials examined, acetal appears the best of the unreinforced polymers and, in particular, nylon 66 was always inferior with higher wear rates and a tendency to form deep cracks in the surface. Of the composites, only the nylon-glass-fibre materials appeared superior to acetal and in these materials the wear process was complex. They appear to offer a somewhat increased load capacity over acetal but only where the required component life is below about 10⁷ cycles.