Rheological probing of structure and pigment-resin interactions in magnetic paints

Dynamic rheological measurements are used to probe the structure of a model magnetic paint which contains iron oxide magnetic pigment particles, a PVC wetting resin and an organic solvent. As the wetting resin concentration, , increases, the viscoelastic moduli, and , go through a minimum at which corresponds to the saturated adsorption of the resin. At the paint is highly elastic, thixotropic and brittle ( sharply drops, G′′ goes through a strong maximum at high strain), which indicates the existence of a strong flocculated network. At the moduli increase due to accumulation of free resin. However, at high the paint becomes less elastic, less brittle and less thixotropic, which indicates that the structure formation in this case is dominated by small aggregates rather than a network. Received: 29 July 1996 Accepted: 29 September 1997