Study On The Preparation Of MWNT Reinforced Water Lubricated Rubber Bearing And Its Friction And Wear Properties

Ship stern bearing is the core component of ship propulsion system.Its friction and wear performance plays an important role in the safety and economy of ships while sailing.However,in practical applications,especially when the ship starts and stops,or operates at a low speed and a heavy load,rubber bearing materials have relatively severe friction and wear.Therefore it is very important to improve the tribological properties of the composites by reinforcing the water lubricated rubber bearing materials.Rubber composites made by adding nanomaterials with self-lubricating properties to the rubber matrix have been proven to have excellent tribological properties.The dispersibility of the nanomaterials in the rubber matrix directly has a crucial effect on the reinforcement of rubber composites.In this paper,nitrile rubber（NBR）is used as the matrix,while MWNT（2phr,4phr,8phr）and MWNT-PDA（2phr,4phr,8phr）are added as reinforcing materials.We explored the effect of the MWNT on the friction and the wear properties of water lubricated rubber bearing materials.And the obtained results are as follows:Dopamine was used to modify the MWNT.The structure and morphology of the MWNT and the MWNT-PDA were observed using a JEM-1400 Plus transmission electron microscope.Fourier transform infrared spectroscopy indicated that there were active functional groups on the surface of the MWNT-PDA.X-ray photoelectron spectroscopy（XPS）was used to determine the change of surface elements and thermos gravimetric analysis（TGA）was used to measure the covering amount of Dopamine.The experimental results show that the surface of the MWNT-PDA has a coating layer with a thickness of about 5nm,and the PDA accounts for about 10.63% of the total weight.The increase of nitrogen and oxygen elements revealed that the functionalized degree have been enhanced after modification.The entanglement of the MWNT-PDA is reduced,which provides a basis for the subsequent preparation of composite materials.Using a combination of solution blending and mechanical blending methods,seven different types of carbon nanotube/nitrile composites（NBR/MWNT）were prepared.And the one with MWNT content of 0 is for reference.Zeiss Ultra Plus field emission scanning electron microscopy was used to observe the dispersion state in the rubber matrix.The results shows that the MWNT-PDA with the added amount of 4phr had the best dispersion in the rubber matrix.The experiments of friction coefficients and wearing capacity of seven kinds of rubber bearing materials are carried out on Rtec-MFT5000 Bearing Test Bed.The friction test shows that the coefficient of friction of rubber bearing materials with modified carbon nanotubes（NBR/MWNT-PDA）is lower than that of original carbon nanotube rubber bearings（NBR/MWNT）.And the friction coefficient of the NBR/MWNT is lower than that of the NBR bearing materials.And among them when the addition amount of MWNT-PDA is 4phr,the friction coefficient of the block reaches the minimum.At this time,various factors affecting the friction coefficient reach a dynamic balance.The wear test shows that,when at the same speed and load,the mass loss of the NBR/MWNT-PDA composite is generally lower than that of NBR/MWNT composite.And when the addition amount of MWNT-PDA is 8phr,the mass loss of the block reaches the minimum.The mechanism of the wear test results was analyzed by measuring the surface micro-morphology.