The primary role of surfactants in emulsion polymerization is to lower the interfacial tension, which allows the emulsification of reactive vinyl monomers and the formation of stable colloidal dispersions of nano-size polymer particles.
Anionic and nonionic are the most effective and widely used surfactants in emulsion polymerization. While anionic surfactants prevent coagulation due to electrostatic repulsions, nonionic surfactants prevent coagulation due to steric stabilization.
Anionic surfactants prevent coagulation by electrostatic repulsions originated from the anionic charges adsorbed on the polymer particles and their associated double layers. And nonionic surfactants, especially polyethoxylates, prevent coagulation by spatial or steric stabilization. Some specialty surfactants, such as fatty alcohol ether sulphates combine both, electrostatic and steric stabilization in their molecules.
The mechanical stability, freeze-thaw stability and shelf-life of paints are all improved by the addition of surfactants. The addition of surfactants to paint also allow the paint to coat a surface more easily because surfactants increase the wetting of a solution.
Surfactants play an important role as cleaning, wetting, dispersing, emulsifying, foaming and anti-foaming agents in many practical applications and products, including: