Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
Surface-Active Agents or Surfactants
Surfactants are molecules having a dual character. Part of each molecule is hydrophilic. Part of each molecule is hydrophobic. The dual affinity means that surfactant molecules have a tendency to accumulate at interfaces between polar and nonpolar phases. Surfactants can help technologists to disperse emulsion particles, spread various liquids onto solids, and stabilize desirable foams. Surfactants can be a nuisance to papermakers when they stabilize undesirable foams, make it more difficult to hydrophobically size paper, hurt dry strength of paper, or hurt fine-particle retention. Rosin soap is a good example of a surfactant; another additive such as alum needs to be used in order to anchor rosin soap to furnish solids so that it can act as a sizing agent rather than as a surfactant. Surfactants are added intentionally to retention aid formulations, biocides, and various sizing agents to keep such products stable during storage.
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