Tribological Properties Of Copolyether Aqueous Solutions With Borate Ester Included

With the sustainable development of resource and the constant improvement of environmental protection concept,green and pollution-free water-based lubricant has attracted more and more interests.However,due to the relatively poor film-formation,lubricity and anti-corrosion performances,it is necessary to select the excellent water-soluble lubricant additives to improve their tribological properties.In this research,dodecanol random copolyether(CPE)and triisopropanolamine borate(BN)are used as additives to study the relevant tribological properties of CPE and CPE-BN aqueous solutions respectively.Firstly,friction wear properties of both aqueous solutions are evaluated with the help of four-ball tribometry to analyze the anti-friction/anti-wear,stability,and extreme pressure charcateristics,and the worn surfaces of steel balls are analyzed by 3D white light interference profiler and X-ray photoelectron spectroscope.The results suggest that the two kinds of aqueous solutions exhibit good friction-reducing peoperty.After adding the BN into CPE aqueous solutions,the anti-wear and stability performances are raised,and the maximum non-seizure load(PB value)increases by 11.6%,which means an improvement in extreme-pressure property.The improvement of CPE-BN aqueous solutions in lubricity is mainly due to the formation of chemical adsorption film and reaction film containing boron-nitrogen compounds during the rubbing process,generating an excellent lubricating effect.Secondly,the rheological behaviors of two solutions are investigated by the rotational rheometer,and the fluid characteristic and viscosity change are analyzed.The results indicate that the two kinds of aqueous solutions present pseudo plastic fluid property with the condition of high concentration.The higher the concentration of aqueous solutions,the higher the viscosity is.The viscosity of CPE-BN aqueous solutions decreases when the BN additive is introduced.Finally,the film-forming performances of both aqueous solutions are studied by means of nano-scale film thickness measuring instrument,and the film-forming ability is analyzed under different loads,concentrations and line speeds.The results show that CPE and CPE-BN aqueous solutions have a good film-forming capacity,and the change of film thickness has little relation with the concentration when the concentration reachs up to 3%.The film thickness of both solutions reduces with the increase of applied load,while it increases with the increasing line speed in a certain range.When the line speed approaches to 500mm/s,the film thickness sustains basically at 25nm.Both of them are in the zone of the thin-film lubrication and the boundary lubrication,and accompanied by mixed lubrication condition.The research results have indicated that the two kinds of water-soluble additives,CPE and BN,possess an excellent synergistic effect in lubrication and have a good prospect of engineering application.They can be used as green water-based lubricant additive.