Mathematical modeling of the magnetic-paper preparation process

The influence of six reaction variables on nine properties of magnetic pape r was investigated. Magnetic properties were imparted through in situ synth esis of cobalt ferrites and then charging these particles into the cellulos e fibers during a lumen-loading step. As a first hypothesis, a multilinear model was selected in which the coefficients of the codified variables were calculated using linear regression by combining two-factorial partial (2(6 -3)) experimental plans. Rather than predicting exact numerical values, the model gives the sign and relative magnitude of the variable coefficients, thus emphasizing the direction for improving magnetic and nonmagnetic prope rties. The results reveal some interesting trends. Above 40 degrees C (the lower temperature limit for spinel formation via coprecipitation), the synt hesis temperature does not play a significant role in any of the studied re sponses except crystallite size. However, higher pulp consistencies improve the ferrite properties. This indicates the importance of the nature of the particles formed in the presence of fibers during the in situ synthesis st ep. The validity of these and other observations was confirmed in subsequen t experiments in which the reaction conditions were adjusted in the directi ons shown by the mathematical models.