Dispersion quality of magnetic tapes prepared from a waterborne formulation

Magnetic tape samples, containing cobalt-modified γ-Fe₂ O₃ pigments, were prepared from a waterborne coating formulation in pilot coating trial. The quality of the pigment orientation and dispersion were characterized using magnetic hysteresis loops and remanence curves. The interparticle interaction field parameter, α, was determined by integrating the δM plot. In general samples having good particle dispersion, as measured by α, also had good particle orientation, as measured by the squareness. However, a number of samples having the same value of squareness had different values of α. The results suggest that a measurement of squareness alone was not an adequate measure of dispersion, but must be supported by remanence measurements. Values of α (-0.369 to -0.261) for the waterborne dispersions approached those of a commercial VHS tape (α=-0.286)