Study On The Properties And Preparation Of Thermostable Magnetorheological Fluids

Magnetorheological fluid(MRF)is a kind of new smart fluid.The special magnetorheological effect that the rheological or viscoelastic properties of the MRF can be controled under magnetic field,which is instantaneous,controllable and reversible.With the magnetorheological effect,MRF has been widely used in civil engineering,aerospace,precision instruments,vibration control,mechanical precision polishing,and so on.When MRF is applied in the auto vibration control,auto transmission and auto brake,the friction between the magnetic particles raises the temperature of MRF and the magnetorheological effect will attenuate or even lead to lose efficacy completely.Therefore,improving thermostability of MRF has become the key determinant for the application of MRF in high temperature work environment.This paper is focused on improving the thermostability of MRF with high temperature resistant biphenyl-diphenyl ether as the base fluid and the sulfonated polystyrene as the surface modifier of carbonyl iron.And the rheological property,sedimentation stability and thermostability were characterized and analysed.To prepare the thermostable MRF,firstly,prepare different sulfonation degree sulfonated polystyrene with polystyrene(molecular weight 150~250 thousand).Then,prepare modified compound carbonyl iron particles with the sulfonated polystyrene.The surface structure,surface properties,crystal structure,magnetic property,surface modification agent content,and element type of the compound particles were analyzed by Infrared spectrum,Scanning electron microscope,contact angle analysis,X-Ray Diffraction,Vibrating sample magnetometer,Thermogravimetric analysis and Element analysis.The consistency between the diphenyl-diphenyl ether and the compound particle was enhanced by the chelation of the sulfonated polystyrene with the carbonyl iron.The thermostable MRF was prepared by compound particles and the diphenyl-diphenyl ether.The rheological property and magnetorheological effect under differrnt temperature was analyzed the magnetic rheological test system,the influence of temperature,modifier content and compound particles concentration on the sedimentation stability was analyzed by the thermal conductivity method.The sedimentation stability and thermostability of the MRF were enhanced.All these attributed to the following points:(1)The sulfonated polystyrene with different sulfonation degree was successfully prepared with polystyrene and sulfonating agent,and the sulfonated polystyrene with sulfonation degree 0.28 is most suitable to be used for surface modifier for the MRF.(2)Sulfonated polystyrene can greatly improve the compatibility between the compound particles and biphenyl-diphenyl ether.Under the molecular inter-atomic forces,the sedimentation stability of MRF is improved.(3)With the low thermal expansion coefficient biphenyl-diphenyl ether,the MRF has very small volume expansion coefficient under high temperature.The prepared MRF can work at higher temperature than the common MRF and it will enlarge the engineering application fields of MRF.