Coalescing Agents: Enhancing Film Formation in Modern Coatings
Coalescing agents are slow-evaporating, water-soluble or water-miscible organic solvents that are essential additives in water-based paints, coatings, and adhesives. Their primary function is to temporarily plasticize the discrete polymer particles (latex) in an emulsion, allowing them to fuse together into a continuous, durable film as the water evaporates. During the drying process, water leaves the coating first, concentrating the polymer particles and coalescent. The coalescent then solvates and softens the particle shells, reducing their glass transition temperature (Tg) and enabling them to merge (coalesce) under capillary forces. Once film formation is complete, the coalescent slowly evaporates from the film over days or weeks, allowing the polymer to regain its original hardness and full protective properties. Without a coalescent, many polymer emulsions would dry to a brittle, powdery, or cracked film, especially at lower application temperatures.
The selection of an effective coalescent is critical to coating performance and regulatory compliance. Common…