Waterborne pressure-sensitive adhesives (PSAs) are the largest class of PSAs by production volume, and most waterborne PSAs comprise polymer dispersions in water. Typically, the major component of a PSA dispersion is a hydrophobic copolymer of acrylic, styrenic, or other vinyl monomers made by emulsion polymerization.
The emulsion polymerization process utilizes hydrophilic components such as water-soluble monomers, water-soluble initiators, surfactants, rheology modifiers, and salts that remain in the final PSA dispersion either associated with the polymer particles or free in the aqueous phase.1 Water-soluble monomers such as acrylic acid (AA) or 2-hydroxyethyl acrylate may copolymerize with more hydrophobic monomers so that the resulting polymer is amphiphilic, displaying hydrophilic groups on the polymer particle surface, or they may form hydrophilic polymers that remain dissolved in the aqueous phase.