Transverse susceptibility and polymer adsorption of magnetic ink

The effect of polymer adsorption on the dispersion of magnetic inks was investigated. Co-/spl gamma/Fe/sub 2/O/sub 3/ particles were treated with pyridine and phenol to poison acidic and basic sites present on their surfaces. The adsorption of a PVC polymer containing sulfonic acid functional groups was decreased with both chemicals, particularly when combined. Transverse susceptibility and rheology measurements were used to evaluate the degree of the dispersion of the magnetic inks. A proposed model for polymer conformation on the particle surface is used to explain the results. We demonstrate the need for both acidic and basic sites fur good dispersion and high magnetic susceptibility.