The effect of glassfibre, graphite and MoS2 on the tribological performance of a liquid crystalline polymer

A thermotropic liquid crystalline polymer (LCP) with a high melting point of approximately 400 °C, unfilled and filled with glassfibre, MoS2 or graphitic carbon was tested in dry sliding contact with steel. Three different test methods were applied, i.e. measurement of coefficient of friction and specific wear rate vs. contact temperature; determination of load-carrying capacities at three different values of sliding speed, and friction and wear behaviour in 20 h tests under relatively severe conditions of load and sliding speed. It turned out that only glassfibre-containing materials perform adequately as dry-running bearing materials, provided that the contact temperature quickly rises above a critical value of the order of 125¿140 °C. In load-carrying capacity tests and in 20 h tests under severe conditions, adding graphitic carbon to glassfibre-containing LCP is particularly beneficial, as this substantially increases the thermal diffusivity of the material. Thus it is concluded that glassfibre- and graphitic-carbon-containing LCP is perfectly suitable for use as a dry-running bearing material at elevated temperatures.