Improving Tribological And Vibration Properties Of Polymer Materials Using Multi-Walled Carbon Nanotube (MWCNTs) For The Water-Lubricated Bearings

The water-lubricated stern bearing is an indispensable support component of the ship propulsion system,which plays the role of transmitting the power of internal and external devices.The triological properties of the water-lubricated stern bearing directly affect the stability,reliability,and service life of the ship.Polymer materials have been widely used in the field of ship stern bearings due to their environmentally friendly features,process easily,good corrosion resistance,wear resistance,and chemical stability.Owing to the poor thermoplastic properties and easy deformation of the polymer,it is prone to plastic deformation,flow,and flaking during the friction process under low-speed and heavy-load conditions.Thus,the addition of nanoparticles with excellent properties is regarded as one of the most important methods for improving the tribological properties of polymer materials.In this paper,I selected multi-walled carbon nanotubes(MWCNTs)and four-needle zinc oxide(T-ZnO_w)to modify high-density polyethylene(HDPE)to investigate the mechanical properties,tribological properties,friction vibration,and noise signals in the process of friction.Moreover,we can also analyze the influence mechanisms of MWCNTs and T-ZnO_w on the friction and wear behavior of modified HDPE,which provide a theoretical basis for designing new water-lubricated bearing polymer materials with low coefficients of friction(COFs)and vibration reduction.The main research contents of the paper are as follows:First of all,HDPE,MWCNTs,and T-ZnO_w particles were matched with different design proportions and thoroughly mixed using an internal mixer and a crusher.We inject the mixed materials into test specimens through an injection molding machine.Then,X-ray diffractometers(XRD),Raman spectroscopy,and energy disperse spectroscopy(EDS)were used to characterize the composition of the modified polymer,and their mechanical properties were detected by the mechanical property testing equipment.The results show that MWCNTs significantly improve the tensile strength,shear strength,tear strength,and shore hardness of the polymer materials.T-ZnO_w enhances the shore hardness and compressive strength while reducing elongation at break and compressibility.The low-speed and heavy-load experiments with the modified HDPE under different working conditions were carried out by a friction and wear testing machine.We analyze and compare synthetically synthetic mechanical properties,COFs,contour curves,wear volumes,and wear surface morphologies of modified HDPE.The results indicated that MWCNTs or T-ZnO_w obviously enhanced the mechanical properties of polymer materials and weakened the deformation behaviours at the wear interface,which resulted in reductions of COFs and wear volumes under dry and water-lubricated conditions.HDPE modified by 7.5% MWCNTs or 6% T-ZnO_w presented the best COF reduction and wear resistance improvement.The coupling modification of MWCNTs and T-ZnO_w further enhanced the tribological properties of HDPE compared to the addition of MWCNTs or T-ZnO_w.At the same time,the coupling modifications of MWCNTs and T-ZnO_w have enhanced the tribological properties of HDPE compared to the addition of a single additive,and the effect mechanisms of the MWCNTs and TZnO_w were revealed by establishing the physical models.By analyzing the friction vibration and friction noise data,it can be known that the addition of MWCNTs and T-ZnO_w can improve the vibration and noise behaviour of modified HDPE polymer materials during friction and wear.The experiment results show that MWCNTs and T-ZnO_w can reduce acceleration and the cycle’s time of frictional vibration and noise signals in modified HDPE polymer materials.The frequency domain spectrum shows that the characteristic peaks of frictional vibration and noise were greatly reduced after the modification of MWCNTs and T-ZnO_w.When the contents of MWCNTs and T-ZnO_w are 2% and 8%,respectively,the friction and vibration performances are the best.The knowledge obtained in this research would be useful to understand the effects of MWCNTs and T-ZnO_w on polymers’ friction mechanisms,which is important for developing new polymer matrix composites with good wear-resistant and vibration properties.