Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
The streaming potential method is one way to determine the charged nature of fiber surfaces. The principle is similar to that of streaming current measurements, with a few subtle differences. Instead of plastic surfaces, the liquid flows through a pad of fibers from the sample itself. A known pressure is used to push the liquid. A resulting voltage is measured between electrode probes on either side of the pad. This voltage is then compared with the voltage at zero applied pressure. Streaming potential is related to zeta potential by factors that include the electrical conductivity, fluid viscosity, and the structure of the fiber pad. The value of streaming potential under given conditions of conductivity and pressure can be used to judge how strongly the furnish will interact with anionic or cationic additives. Better yet, one can titrate the streaming potential value to zero and get a very accurate measure of the cationic or anionic demand of the furnish.
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