Testing the structure of magnetic paints with and without superimposed shear

The structure development in dispersions of magnetic barium ferrite particles in cyclohexanone with polyvinylchloride wetting resin was tested by oscillatory rheological measurements and orthogonal superposition of steady and oscillatory shear. The optimum dispersion is achieved at the resin concentration c=c0, which corresponds to a minimum in the viscoelastic modulii. At cc0 the system becomes less elastic, more flexible, less thixotropic and H(τ) is dominated by short τ, which indicates that the structure formation in this case is dominated by small aggregates rather than a network. By superimposing steady and oscillatory shear we show that the steady shear dramatically break the structure and shifts H(τ) to very short τ