ANALYSIS OF THE MIXING CONDITIONS OF A TONER DISPERSION

Twin screw extruder mixing of a typical black toner formulation was in vestigated under different mixing conditions. The intensity of the mix ing was varied by changing the feed rate of the material and the screw rpm of the extruder. Microstructural changes in the particulate fille rs mere analyzed by transmission electron microscopy. The fillers were characterized in terms of their particle size and shape distributions and spatial distributions within the binder. Changes in the molecular structure of the binder polymer were identified by gel permeation chr omatography and softening temperature measurements. Temperature-variab le dielectric properties and rheological properties of the bulk materi al samples were investigated as possible tools for understanding the d egree of dispersion. Results indicate that both methods are sensitive to the changes introduced by different processing conditions. Charging properties of the pulverized samples were also characterized. Both ch arge per unit mass values and charge distributions of the toner partic les were found to be adversely influenced by increasing intensity of m ixing.