DISPERSION QUALITY OF MAGNETIC TAPES PREPARED FROM A WATERBORNE FORMULATION

Magnetic tape samples, containing cobalt-modified gamma-Fe2O3 pigments , were prepared from a waterborne coating formulation in a pilot coati ng trial. The quality of the pigment orientation and dispersion were c haracterized using magnetic hysteresis loops and remanence curves. The interparticle interaction field parameter, alpha, was determined by i ntegrating the delta M plot. In general samples having good particle d ispersion, as measured by alpha, also had good particle orientation, a s measured by the squareness. However, a number of samples having the same value of squareness had different values of alpha. The results su ggest that a measurement of squareness alone was not an adequate measu re of dispersion, but must be supported by remanence measurements. Val ues a (-0.369 to -0.261) for the waterborne dispersions approached tho se of a commercial VHS tape (alpha = -0.286).