Influence of temperature on friction of polymeric materials in water

The operating conditions, particularly lubrication and heat dissipation of water-lubricated stern tube bearings can be adversely affected by marine life attached to the propeller and bearing housing. This can increase the temperature of the water in the stern bearing, which could seriously degrade the water-lubricated bearings. In this reported study, the friction behavior of nitrile rubber (NBR), ultrahigh molecular weight polyethylene (UHMWPE), UHMWPE/NBR composites (abbreviated as NU), and polymer resin (abbreviated as PR) against a copper alloy shaft was investigated using a water-lubricated sliding test at different water temperatures. The water temperature was varied from 20 to 80°C. Dynamic thermomechanical analysis (DMA) and scanning electron microscopic (SEM) observations were used to characterize the thermal transitions and reveal the wear patterns of the test materials. The results showed that the friction coefficient of the NBR and UHMWPE/NBR composites exhibited a slight increase with increasing temperature. It was found that the variations in test temperature had less of effect on the friction behavior of the UHMWPE. When the test temperature exceeded 60°C a significant increase in friction and wear of the polymer resin was observed. The experimental results showed that there was a direct relationship between water temperature and tribological behaviors of the polymers which should be considered in the selection and design of high performance water lubricated materials.