Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
Charged Patch Model
The charged patch model is one of the descriptions that scientists use to account for the main effects of highly charged cationic polyelectrolytes having molecular masses in the approximate range of 100,000 to 2 million grams per mole. The patch model appears especially appropriate in cases involving polyelectrolytes having a branched structure adsorbing onto surfaces of opposite charge. The adsorbed patch of polymer can serve as an anchoring point for another bare surface of the same type as the first. The strongest evidence in favor of a charged-patch mechanism is the partial reversibility of certain flocculation, retention, and drainage phenomena. In other words, particles that have been detached from each other by strong hydrodynamic forces can be effectively linked together again by the charged patches. By contrast, polymeric bridges between suspended particles tend to be irreversibly broken by high levels of shear.
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