Fabrication And Performance Investigation Of Natural Rubber Based Magnetorheological Elastomers

Magnetorheological elastomers(MREs)are a new branch of intelligent and smart materials of magnetorheological material,which are mainly composed of a rubber matrix and soft magnetic particles.Based on this unique advantage,MREs have been considered for vibration control in the fields of military,vehicle,civil engineering and medical.However,the MREs have problems such as poor mechanical properties,low magnetorheological effect and excessive damping performance,which makes it unable to meet its practical application.In this paper,the mechanical properties of MREs are optimized by experimental methods.Firstly,the magnetorheological elastomer was prepared by using natural rubber with good mechanical properties as the matrix,and the effect of particle type on the properties of MREs was studied.Then,from the perspective of matrix,the effect of vulcanization system on the crosslink structures and mechanical properties of MREs was studied.Finally,the effect of silane and titanate coupling agent on the properties of magnetorheological elastomer was studied from the perspective of enhancing the interaction between particles and matrix.Details are described as following:Firstly,the effects of carbonyl iron powder,iron-silicon particles and iron-siliconaluminum particles on the morphology,dynamic mechanical properties and thermal oxidation stability of MREs were investigated.The results showed that the magnetic-induced modulus and magnetorheological effect of the MRE sample filled with carbonyl iron powder are higher than those of the samples filled with iron-silicon particles and iron-silicon-aluminum particles,respectively.The main reason is that the saturation magnetic induction strength of the carbonyl iron powder is high,and thus the MRE sample filled with the carbonyl iron powder shows better magnetic properties.However,it was also found that the sample filled with the carbonyl iron powder was inferior in thermal oxidative stability and the Payne effect was relatively remarkable,which was disadvantageous.Then,the effects of conventional(CV),semi-efficient(semi-EV)and efficient(EV)vulcanization system on the crosslink structures,morphology,curing properties and dynamic mechanical properties of MREs were investigated.It was found that the content of polysulfide linkages decreased and the monosulfide linkages increased when the vulcanization system was changed from CV to semi-EV and EV vulcanization system,respectively.The crosslink density has the same tendency with the content of polysulfide linkages.As the crosslink density decreased,the torque,initial storage modulus,saturation magnetic-induced modulus,and Payne effect of all samples increased.By studying the mechanism of influence of the vulcanization system,it was found that this was because of the longer and more aligned particle chains in a sample with low crosslink density.The results also show that as the proportion of monosulfide linkages increased,the value of the loss factor increased and the modulus of the MRE sample was more affected by the increasing frequency.This work is expected to provide guidance for the vulcanization system selection of MREs.Finally,the effects of silane and titanate coupling agents on the properties of MREs were investigated.First of all,the effect of sulfur-containing silane coupling agent on the properties of MREs with various vulcanization systems was investigated.It was found that the hydrophobicity of the surface of the carbonyl iron powder modified by the sulfur-containing silane was significantly improved,and the interfacial compatibility between the particles and the rubber matrix with various vulcanization systems was also significantly improved.It was also found that after the modification of the carbonyl iron powder by the sulfur-containing silane,the initial storage modulus and saturation magnetic-induced modulus of samples of all vulcanization systems increased,and the Payne effect of the zero field and damping were decreased.Moreover,these changes are more evident in the sample of EV system.However,the addition of sulfur-containing silanes also resulted in a decrease in the magnetorheological effect of the samples of all vulcanization systems.Then,the effect of titanate coupling agent on the properties of magnetorheological elastomer was studied and compared with the enhancement efficiency of silane coupling agent.The results show that the titanate gives the carbonyl iron powder a higher surface hydrophobic property and better compatibility with the rubber matrix than the sulfur-containing silane,so that the magnetorheological elastomer has a higher saturation magnetic-induced modulus and magnetorheological effect.The differences between them are mainly related to their own structures and the way they are combined with the rubber matrix.The above results will provide a feasible solution for the development of high-performance MREs and provide a theoretical and experimental basis for its application in vibration control.The present study is still primary and rough,and further work is expected to make them perfect.