Research On Water Based Lubricating Properties Of Polyethylene Glycol As Additive In Surface Contact

With the rapid development of global economy,the problem of oil depletion,energy crisis and environmental pollution have become increasingly serious.Water-based lubricant instead of oil-based lubricant gets widely attention,because of its advantages of low cost,convenient storage and transportation,and large resource.However,the additives are always needed to add to water-based lubricants to overcome their disadvantages,such as poor lubricity and corrosion resistance.In recent years,more and more studies have found that water soluble polymer,when added into water,not only can effectively improve the viscosity of water,but also can form thick lubricating film to prevent the contact between the metal in relative sliding.Therefore,the tribological properties of water-based lubrication could be effectively improved.In this paper,low molecular weight polyethylene glycol which is non-toxic,biocompatible and water-soluble is used as water-based lubricant additive.The tribological properties of water-based lubricant are systematically studied by using quartz friction pairs in the condition of surface contact.In order to improve the tribological properties of polyethylene glycol,the metal ions and glycerol are added to polyethylene glycol aqueous solution.The main contents are as follows.The water-based lubricating properties of low molecular weight polyethylene glycol aqueous solution are studied.The influence of molecular weight,load and the mass fraction on the lubricating properties are emphatically analyzed.The experiment results show that,it has excellent lubrication performance in the low speed and low load condition,and the lowest friction coef'ficient can reach 0.0012,in the state of super-lubrication.This indicates that polyethylene glycol can be used as effective water based additive.With the increasing of molecular weight,load and the mass fraction,friction coefficients of all lubricants reduce.As the increase of molecular weight and mass fraction,the wear tracks of friction pairs reduce and the surface roughness become small.The experiments also found that,with the increase of load,the wear track of friction pairs increases,but the surface roughness decreases,when mass friction is largest value 10%and molecular weight is equal to 1000.The influences of alkali metal ions on the tribological properties of low molecular weight polyethylene glycol aqueous solution are studied.The experiments found that,friction coefficient of all lubricants decrease after adding the alkali metal ions,and the lowest friction coefficient reduced from 0.0013 to 0.0007.The wear tracks of friction pairs and the surface roughness decrease.With the increase of mass fraction,the friction coefficients reduce in turn in the order of K+>Na+>Li+,Ca2+>Mg2+.The influence of glycerol on the tribological properties of low molecular weight polyethylene glycol aqueous solution is analyzed.The experiment results show that,glycerol can reduce the friction coefficient of all lubricants.The wear tracks of friction pairs lessen and the surface roughness decrease.With the increasing of mass.fraction,the friction coefficients reduce.In different lubricating conditions,the reducing rate of friction coefficient is in the order of PEG200>PEG600>PEG1000,in which the biggest change is 21.6%.