Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
The zeta potential is defined as the average electrical potential at a hydrodynamic slip plane adjacent to a solid surface exposed to a liquid. Zeta potential data provide the papermaker with a way to predict how a furnish is likely to respond to the addition of cationic or anionic additives. A furnish having a zeta potential near to zero is more likely to drain well, especially if the drainage mechanism is dominated by additives having low molecular mass. Slurries of mineral fillers, sizing emulsions, etc., that have high absolute values of zeta potentials (say greater than plus or minus 20 mV) are likely to remain in stable dispersion during storage. Microelectrophoresis is the most common way that papermakers evaluate the zeta potential of fiber fines and fillers. Commercially available fiber-pad streaming potential devices often output a nominal "zeta potential," but it is important to keep in mind that such output is not expected to agree with results from microelectrophoresis. The zeta potential is a good predictor of the magnitude of electrical repulsive forces between particles of known size and shape as a function of distance.
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