Tribological Performance of a Polymer Blend of NBR Used for Stern Bearings

Nitrile-butadiene rubber (NBR) and another polymer with an excellent self-lubricating property are blended to develop a new kind of polymer used for water-lubricated stern bearings. The tribological performance of the new Polymer Blend of NBR (PBN), with the comparison of a rubber common used for most stern bearings, was studied using a stern bearing test rig of SSB-100. The results showed that the friction coefficients of PBN are lower than those of NBR under water-lubricated conditions. And the difference is the most evident at speeds of 0.1 ~ 2.0m/s. So PBN will change to Plasto-Elastohydrodynamic (PEH) Lubrication at lower speed to reduce the critical speed of bearing squeal. This indicates blending rubber with other polymers is an effective means to develop low-friction stern bearing materials. Furthermore, test results revealed that reducing the rubber layer thickness and hardness will reduce the friction coefficients. So in the structure design of water-lubricated rubber bearings, selecting proper structural parameter will improve the tribological performance.