Preparation And Properties Of Composite Hydrous Electrorheological Elastomers

The aim of the paper is producing the wet bionic intelligent materials. Based on theories of the Electrorheological (ER) effect, we have prepared the ER composite hydrous elastomers, with the gelatin hydrogel as the matrix containing inorganic and organic dispersed particles. The influences on the response behavior to an applied electric field have been studied. The intelligent hydrogel possessing a good ER property will be developed.The study has prepared the barium titanate/gelatin water-based elastomers, starch/glycerin /gelatin water-based elastomers and barium titanate/gelatin/ glycerin water-based elastomers. The structure of the dispersed particles in them, and the mechanical as well as electrical properties of them, have been investigated by micro-observation of particles, tests of compression modulus of the elastomers, as well as dynamic measurement of electric resistivity and permittivity of the elastomers. The experimental results are given as follows:1. Barium titanate particles were dispersed in the gelatin water solution. With or without an applied dc electric field respectively, the admixture was cured to the two hydrous elastomers via cooling and chemical crosslink. The behavior of particles was observed by a microscopic method. The mechanical properties of the elastomers were described with the compression modulus as a function of both particle concentration and field intensity. The result demonstrates that there is an obvious difference between particles dispersion in the two elastomers, which cured with and without field. Also, the large difference is between the responses to field of the two elastomers. The particles were aligned in the matrix under a field, and then the particles' alignment increased the elastomer's compression modulus and responses to field. In addition, both the chain effect and filler effect of the particles can dominate the modulus. The peak of modulus appears in the elastomer with a particle weight fraction of 1.5% because of the complex dominations of the two effects. In like manner, the largest response to field appears. Based on the results, we found that the modulus of the elastomer, cured under field, is greater than that without field, and increases with the increasing field, either for curing or for measuring.2. For improving the particles' dispersion in matrixes, enhancing the stability of the matrixes, and preparing a steady and friendly elastomer, the starch particles, a crude organic macromolecule with light density, was dispersed in the glycerin/ gelatin/water composite solution. With or without the field respectively, the composite solution was cured to the two hydrous elastomers via the similar method. After testing the compression modulus and dynamically measuring the electric resistivity, the results suggest that the compression moduli of the elastomers increased evidently with the increasing field intensity and the weight fraction of particle. The largest modulus appeared with 25% starch. According to the dynamic measurements of electric resistivity, it is shown that an applied electric field made particles disperse orderly in matrixes and form chain structure, which induced the response to the field to become strong, the modulus to heighten and the resistivity to increase.3. In order to investigate ulteriorly the ER behaviors of the composite hydrous elastomers and the influential factors to them, we have prepared and studied the elastomers containing barium titanate nanorods. The barium titanate nanorods were synthesized by inverse micelle method and low-temperature solvothermal process, whose diameter and length is about 80～100 nm and l～2μm, respectively. The gelatin/glycerin water-based elastomers containing barium titanate were produced with similar method. According to testing the storage modulus and dynamically measuring the permittivity, the results indicate that the properties of the hydrous elastomer systems were influenced not only by an applied field and weight fraction of particle, but also by the shape and size of particle. With increasing the field intensity, modulus of the elastomer boosted up anteriorly and decreased posteriorly, and generated a peak at the field intensity 1kV/ mm. On opposite, the permittivity of the elastomer decreased anteriorly and increased posteriorly, and generated a hollow at the field intensity 1kV/ mm. With the weight fraction of particle increasing from 0.5wt% to 2.5wt%, the modulus and permittivity of the elastomer generated a peak and a hollow at 1.5wt%, respectively. With the volume fraction of nanorod in particles increasing, the modulus increased and the permittivity decreased.4. According to physical and chemical theories, as well as the experiment results, we considered all things and summarized that the ER effects of the gelatin hydrogel composite elastomers are influenced by the factors of the dispersed particles and the matrixes, for example, the particle's permittivity, density, shape, size and weight fraction, as well as the matrix's stability and elasticity. The property of matrix is the foundation of a good ER effect of the hydrous composite elastomer, the property of dispersed particle is the entrance of improving the elastomer's ER behavior. All factors, which are in favor of particle's dispersion or polarization, can promote the ER performances. The externally applied electric field is the main force of controlling elastomer's behavior.