Mini-Encyclopedia of Papermaking Wet-End
Part Two: Definitions and Concepts
Hydrophobic means "water-hating." Chemical groups that tend to make substances hydrophobic include -CH2- chains and rings (hydrocarbons). These substances lack the ability to hydrogen bond and their surface free energy is relatively low. Water does not tend to wet hydrophobic surfaces; rather, the droplets stay beaded up with high values of contact angle. Internal sizing agents such as rosin, ASA, and AKD depend on hydrophobic groups in order to perform their function. The opposite of hydrophobic is hydrophilic, water-loving. Surface-active agents contain both hydrophobic and hydrophilic groups on the same molecules.
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