Rheology of silica suspensions stabilized by ethylenediamine

The effect of ethylenediamine bridging, particle size and specific surface area of fumed silica on rheological properties of silica suspensions were studied with a cylinder rheometer. The apparent viscosity of suspensions of aerosils A-50, A-175, A-300 and A-380 irreversibly increases with shearing time at shear rates above a certain value. The critical shear rate for shear-induced bridging coagulation decreases with the increasing ethylenediamine concentration because of lowering of the energy barrier due to a compression of the electrical double layer. The suspensions become elastic pastes after the bridging coagulation.