Electrorheology of filled silicone elastomers

Electrorheological (ER) silicone elastomers containing particles based on silica (SiO2) and titania minerals (BaTiO3, Ba2Ti9O20, and BaTiO3/CaZrO3) were prepared and characterized. An electrical field was applied to align the particles during the cure of the silicone prepolymer. For the: silicone/silica compositions, a prominent Maxwell-Wagner dispersion in the dielectric response suggested that surface conductivity of the silica particles dominated the polarization. Alignment of the particles increased the overall dielectric permittivity as well as the magnitude of the Maxwell-Wagner dispersion. Their ER response exhibited a negative deviation ft om a quadratic dependence on field intensity at high fields, and was accompanied by nonlinear conductivity. A highly nonlinear enhancement of the ER effect with increasing particle concentration was observed. For the silicone/titania elastomers as a class, the ER response increased with the particle's permittivity. In the case of the silicone/BaTiO3 elastomer, the ER effect increased with held frequency, as expected from high permittivity of BaTiO3 relative to silicone, whereas the opposite dependence was observed fur the silicone/silica ER elastomer, suggesting a conduction polarization mechanism for the latter. (C) 2001 The Society of Rheology.