Study On Three Dimensional Structure Enchanced Magnetorheological Elastomer

Magnetological elastomers (MREs) are smart materials consisting of micrometer size soft magnetic particles and elastic high polymers. The mechanical properties of MREs change continuously and reversibly with an external magnetic field. Owing to these special properties, MREs are widely used in noise reduction and vibration control, etc.Matrix modification or particle modification can improve the mechanical properties, storage modulus and the damping propertites of the MREs. So the main research objects on MREs are matrix and magnetic particles. However, the structural design of MREs has not attracted enough attention. The classical structure of the MREs is that the soft magnetic particles are oriented in a matrix to form chain structures. The linear structures are very important for the MREs. However, since the lack of support skeleton, the linear structure could be easily broken when subjected to the shear stress. As a result, the structural design of MREs was very important and meaningful to obtain ideal storage modulus and magnetorheological (MR) effect.Here, a three-dimensional network structure is selected to enhance the mechanical properties of MREs. The influence of the skeleton structure on MREs performance is systematically studied. By doping rosin glycerin ester to the natural rubber, the effects of matrix wettability on MR properties of MREs were studied. Moreover, the polyurethane sponge skeleton was selected to strengthen the MREs and the effect of matrix on the chain structure of carbonyl iron powder in MREs was studied. Carbon nanotubes and sliver nanowires were further deposited on polyurethane sponge to achieve the conductive MREs. The influence of strain and magnetic field on the resistance of MREs was carefully discussed. These works improved the mechanical properties of MREs and extended their application to the sensor field. The details are as follows:The rosin glycerin ester was added into the natural rubber matrix to increase the wettability and dispersibility of carbonyl iron powder in natural rubber matrix, thus further enhanced the mechanical properties of the MREs. The effect of the wetting ability between matrix and carbonyl iron powder on the mechanical properties of MREs under different magnetic field, strain and frequency was studied. In comparison to the pure natural rubber matrix, rosin glyceride/natural rubber matrix shows better wetting performance, so the damping of MREs was reduced. The addition of rosin glycerin eater also increases the magnetic induced modulus of MREs. In this work, the wetting ability between matrix and carbonyl iron particles was studied, which was helpful to improve the mechanical properties of MREs.The MR plastomers were injected into the porous sponge structure to prepare noval MREs. The effect of 3D skeleton on the inner iron powder of MREs was studied. It was found that the 3D skeleton could greatly enhance the magnetic induced modulus and MR effect. Due to the elastic characteristic of the porous polyurethane sponge skeleton, the as-prepared MREs can be repetitively stretched and bent. It is observed that the porous framework in the MREs can effectively distribute the shear force to the MREs, and simultaneously increase the zero-field storage modulus and the magnetostriction modulus of the MREs. The implantation of the porous skeleton had little effect on the damping capacity of MREs. This method provides a feasible scheme for increasing the magneto-moduli of MREs and improving the mechanical properties of MREs, which is of great significance to their engineering application.Further researches on the inner three-dimensional network structure of MRE have been carried out. The effects of cross-linking degree, strain and magnetic field on the resistance of MREs were systematically studied. The results showed that the resistance of MREs varied with strain and magnetic field. Flexible carbon nanotubes had enhanced the storage modulus and magnetostriction of MREs. After coating sponge with carbon nanotubes, the electrical conductivity of MREs was greatly improved and its resistance changed regularly with strain. This special feature extended MRE’s applications to the area of strain sensors. While coating the sponge with silver nanowires, the storage modulus and magnetostriction of MREs decreased. However, due to the good conductivity of silver nanowires, the resistance of MREs is more sensitive to strain, and the resistance was critically dependent on the magnetic field. Therefore, MREs can be used as a magnetic field sensor. In addition, the effect of matrix cross-linking degree on the resistance of MREs was investigated. The above research expands the application of MREs in sensor field.