This slows the process of demulsification and stabilizes the latex paint.

Demulsification is the act of destabilizing an emulsion.

Surfactants lower the surface tension (γ) and thus gibbs energy is gained from demulsification.

Demulsification is beneficial for several macroemulsion applications.

The energy gained from demulsification is dependent on the total area of interface and the surface tension of that interface.

The thermodynamic explanation for demulsification is the gain in Gibbs Free Energy resulting from lowering the total area of high energy surface interactions.

Macroemulsions in latex paint are inherently unstable and phase separate, so surfactants are added to lower interfacial tension and stabilize polymer particles to prevent demulsification.