FRICTION AND WEAR BEHAVIOR OF 18 POLYMERS IN CONTACT WITH STEEL IN ENVIRONMENTS OF AIR AND WATER

18 polymers were characterized with respect to their friction and wear behaviour in contact with steel in environments of air and water. These were six unfilled materials, i.e. polyamide 66 (PA 66), polyoxymethylene (POM), polyethyleneterephthalate (PETP), polyetheretherketone (PEEK), polyphenylenesulphide (PPS) and polyetherimide; also, the same base materials filled with polytetrafluoroethylene (PTFE) or PTFE plus glass fibre were used. Two types of experiments were performed, i.e. measurement of the coefficient of friction f as a function of the contact temperature T(c) ("f-T(c) diagrams"), and measurements of friction and wear in 20 h tests. The f-T(c) diagrams were obtained in air; the 20 h tests were performed in air and in water at a temperature of 20-degrees-C. In air the polymers ran against rings of ball-bearing steel (AISI 52100); in water the rings were made of stainless steel (AISI 316). It turned out that in air addition of PTFE was generally beneficial; PA 66, POM, PETP and PEEK, all filled with PTFE, performed exceptionally well (specific wear rates k appreciably lower than 1 X 10(-15) m3 N-1 m-1). In water, however, PTFE did not function at all. Now PA (with or without PTFE), unfilled POM and PETP filled with PTFE and glass fibre met the k < 1 X 10(-15) m3 N-1 m-1 criterion. With a few exceptions, addition of glass fibre produced unfavourable effects, in air as well as in water. The observed phenomena are explained tentatively in terms of polymer structures and transfer and wear mechanisms, whereby special attention is paid to the ratio of friction over strength.