Study On Lubrication Performance Of Polymer Brush Under Unconformal Contact

Synovial fluid provides excellent water lubrication performance for joint contact area,this magical biology lubrication properties has attracted more and more scholars to study,based on the inspiration of natural synovial joint microstructure and lubrication mechanism,scientists found that ultra-low friction properties and good biocompatibility of the surface graft polymer brush in the water environment,more and more domestic and foreign scholars began to research surface grafting polymer brush this advanced bionic lubrication technology.In recent years,research on polymer brushes are basically around the microscopic research,namely the friction force and friction coefficient were characterized under various conditions.However,macro characteristics research of polyelectrolyte brush is relatively less.This paper is supported by Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences,lubricating properties of the interface of polymer brush under unconformal contact in the three lubricants was studied,using the surface contact thickness measurement device,the sample slider and the transparent glass plate were used as the surface contact pair which include:1)Experimental study of polyelectrolyte brush in deionized water: The experimental results show that the contact angle of deionized water on the surface of the grafted PSPMA sample demonstrates the hydrophilicity of the PSPMA.The comparison with the optical curve of the smooth block demonstrates the swelling of the polyelectrolyte brush.The smooth sample did not form an effective lubrication film thickness on the load of 2N,the inclination of 1/1474 and 1/747,and the PSPMA-modified sample block formed a certain effective lubrication film thickness in deionized water,The presence of polymer brushes contributes to the formation of surface water film and the linear relationship between the film thickness and the velocity curve is not linear at the lower velocity.With the increase of the velocity,the film thickness gradually becomes linear with the rotational speed.The swellingof the polymer chains was complete and the formation of the water film was based on the hydrodynamic effect of the contact zone.The film thickness formed by the PSPMA modified specimen decreases with the increase of the load(within a certain load).According to the superabsorbent properties of polymer brush in deionized water,exploring the wear and tear of the polymer in the movement.The results showed that with the increase of entrainment speed and load,the surface of grafted polymer brush contact angle increases,the surface polymer chain wear increased.2)Experimental study of polyelectrolyte brush in salt solution: The experimental results show that,at the loading of 2N and the inclination of 1/1474 and 1/747,the PSPMA-modified specimen can form a film with the increase of the rotation speed in salt solution.The film formed in 0.1mol/L NaNO3 was similar to that formed in deionized water.However,the lubrication film thickness is relatively low in the larger concentration of salt solution;The film thickness of PSPMA was different in different salt solution of three kinds of positive ions,and the film thickness of PSPMA modified sample was lower as the polarity of positive ions in salt solution was lower,so the lubrication performance was decreased.This is consistent with the existing theory.3)Experimental study of polyelectrolyte brush in lubricating oil: The contact angle of PAO and PEG oil on the surface of polymer brush is very low,indicating that PSPMA is lipophilic,but the change of intensity curve shows that the polymer chain does not have oil-swellability.At the load of 2N,the tilt angle of 1/1474 and1/747,polymer brush PSPMA can form a certain lubricating film in oil,but the lubrication effect is lower than the smooth surface;At low speeds,the surface grafted PSPMA samples at high concentrations of PEG formed a slightly higher film thickness than the lower concentration,with the increase of velocity,the film thickness formed in PEG at low concentration was superior to that at high concentration.At the loading of 2N and the inclination of 1/1474,the surface grafted PSPMA samples had similar film thickness in PAO4 and PAO8,and the lubricating effect was better than that in deionized water at low speed,as the speed increases,the lubrication effect is weakened.