Influence Of Particle/matrix Interface Modification On Viscoelasticity Of Electrorheological Elastomers

Electrorheological elastomers(EREs)are a kind of intelligent soft materials made by dispersing polarizable micro-or nanometer-sized particles in insulating rubber or gel materials.The viscoelastic properties(storage modulus,loss factor,etc.)of EREs will present a reversible and quick change when an electric field is applied.Compared with the elastomers such as traditional rubber,EREs can be adapted to different vibration or driving environments owing to their adjustable viscoelastic properties as required.Therefore,EREs have application prospects in intelligent vibration isolation for military aviation,building bridges and precision equipment and other fields like electro drive and artificial muscle.At present,the EREs still have the problems of narrow relative ER effect and high working voltage,which restricts their further application.As one kind of composites,the electrorheological property of EREs is closely related to the surface polarization of filler particles and the interfacial bonding strength between the particles and the matrix.In order to improve the electrorheological proformance of the elastomers,this dissertation fouses on the modification of interface between particles and elastomer matrix with polar molecules and silane coupling agent,and the damping mechanism of EREs and effect of interface.First,according to the polar molecule dominated model,TiO2 particles were coated with urea polar molecules to prepare TiO2/urea particles with complete core-shell structure,and bare TiO2 particles were also fabricated for comparion.Then,the EREs were prepared by using these two kinds of particles as dispersed phase and silicone rubber as matrix.Characterization results of particles show that the TiO2/urea particles have a surface coating about 10 nm in thickness,which should be the urea shell.Since the TiO2/urea particles has enhanced dipole polarization effect on the particle surface,the TiO2/urea particles filled EREs present higher dielectic constant.Meanwhile,the particle/matrix interface is also strengthened after the particles are modified with urea molecules.The dynamic viscoelastic test results indicate the TiO2/urea particles filled elastomer has higher storage modulus than the bare TiO2 particles filled sample within the field strength range from 0 to 3 kV/mm,and it also exhibits higher relative ER effect under low field levels(0?2 kV/mm).Besides,the relative ER effects of the EREs containing the TiO2 and TiO2/urea particles achieve 282 and 266%at 3 kV/mm,respectively,which are 21.6%and 14.7%higher than those in previous studies.3-(trimethoxysilyl)propyl methacrylate and triethoxyvinylsilane were used to modify the interface between amorphous TiO2 particles and silicone rubber afterward.EREs filled with these two kinds of modified particles were prepared and compared with the sample containing bare TiO2 particles.The results of structure analysis show that the crosslink densities of EREs filled with modified particles are higher and some fine wire bridging structures appear between the adjacent particles,which indicates that the interface combination between the particles and the rubber matrix is enhanced by crosslinking between the silane coupling agents on the particle's surface and the silicon rubber molecules.Furthermore,the tensile strength of the silane cooupling agent-modified TiO2 particles is higher than the control group,and the tensile strength of the EREs is positively correlated with their crosslink density.Due to the enhanced interface combination and stronger polarization strength,the ERE filled with TiO2/V1 particles has lower storage modulus without applied electric field and higher storage modulus at 3 kV/mm,and its relative ER effects attains the highest 315%,which is 35.8%higher than that in previous result.Finally,based on the damping capacity test results of EREs filled with TiO2,TiO2/Al and TiO2/V1 particles,the influence factors of damping of which were discussed and the influence of particle/matrix interface state on the damping behaviors had been carried on the selective analysis.Subsequently,an improved theoretical model for damping behaviour of EREs was proposed.The experimental results show that the total damping of bare TiO2 particle filled sample becomes higher than the samples containing modified TiO2 particles when the shear strain beyond?10%.The possible reason is that there is no strongly bonded interface formed by strong chemical bonds between the bare TiO2 particle and the matrix,which means the weakly bonded interface damping of bare TiO2 particle filled ERE is stronger than the other samples in large strain amplitude.For the EREs filled with modified TiO2 particles,the intrinsic damping plays the most important role when the particle content or strain amplitude are at low level.When the strain amplitude and particle content are relatively high,the weakly bonded interface damping plays a dominant role in determining the damping capacity of all the EREs.