Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
Bridging is a term used to describe the ability of certain dissolved polymers to agglomerate suspended particles or to cause flocculation of fiber slurries, especially in the presence of flow. According to the bridging model, the polymer first adsorbs partly onto one surface, and then loops or tails or the same macromolecule become attached to a second surface. Dissolved polymers need to have a molecular mass of at least 2 million grams per mole in order to work effectively by this mechanism. An anionic polyelectrolyte can be a very effective bridging agent and retention aid for papermaking fibers if these have been treated with a cationic material so that there are positive sites on those surfaces.
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