A new rubber/UHMWPE alloy for water-lubricated stern bearings

A new polymer alloy has been developed by blending powder of UHMWPE and graphite into nitrile rubber for marine stern tube bearings. It has good self-lubrication performance, which decreases the friction coefficient under low speed conditions and the critical speed at which bearing vibration and noise occur. Experimental investigations have been completed to examine its physical properties, integrated bearing friction as well as dynamic characteristics of the system in vibration and noise environments. The results show that mechanical and physical properties of new alloy meet the requirements of ship standard CB/T769-2008. Stick-slip occurs at the critical speed of 0.27 m/s. The friction coefficient is only about 50% of the restricted value in USA millitary specification MIL-DTL-17901C(SH)(2005) at or less than the speed of 0.18 m/s, and reached a minimum value at the speed of 0.54 m/s. The permissible maximum value of local projected pressure is 0.7 MPa. The experimental results have confirmed the excellent low-speed performance and comprehensive function of the new Rubber/UHMWPE alloy which may be a good type of water-lubricated materials for marine stem tube bearings.