Electrorheological properties of suspensions of the polyimides based on 4,4’-diaminodiphenylsulfide | Mekhanika | kompozitsionnykh | materialov i konstruktsii

Electrorheological properties of suspensions of the polyimides based on 4,4’-diaminodiphenylsulfide

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Electrorheological suspensions (ERS) of polyimide particles were obtained in various nonconductive dispersion media based on a series of aromatic polyimides synthesized by the single-stage high-temperature polycondensation method on the basis of 4,4′-diaminodiphenylsulfides, dianhydrides of 3,3,4,4-biphenyltetracarboxylic and 1,2,4,5- tetracarbonyl and 3,3,4,4- diphenyloxycarboxylic acids. Their electrorheological properties were investigated in nonconducting medium depending on parameters of deformation and external electric field intensity. It was established that ERS based on polyimide particles possess a powerful electrorheological response that is ten times greater than the ERS response with a dispersed phase based on traditional micro-particle particles. It is shown that polyimide ERS, as a result of an increase in the electric field strength, changes the nature of the flow from the Newtonian type to the pseudoplastic one because of the polarization of the particles and the formation of chain structures along the force lines of the electric field. Complexes with intermolecular and intramolecular charge transfer are formed in the medium. Interactions occur between rich electrons (donors) nitrogen atoms and electron-depleted carbonyl groups (acceptors). These random interactions lead to the formation of additional bonds that increase creep resistance and other physical and mechanical characteristics. The influence of temperature on the change in the rheological and electro-rheological properties of polyimide ERS in constant electric fields was established. It is shown that the electro-rheological effect of polyimide ERS is most pronounced at a temperature of about 45C. It is also shown that the electrorheological effect is more pronounced for the ERS of the polyimide in the transformer oil than in the dibutyl phthalate and PMS-500, which, apparently, is due to the lower dielectric permittivity of the medium.