Ethox

WATERBORNE EPOXY COATING SYSTEMS WITH FREEZE/ THAW STABILITY AND IMPROVED PROPERTIES

By: Charles F. (Chip) Palmer

Waterborne Epoxy Coating Systems

Waterborne two component epoxy/amine formulations can be an attractive alternative to solvent-based systems despite their higher cost and – in some respects – slightly reduced performance. Whereas the main driving force pushing waterborne system comes from environmental, safety and health considerations, there are also applications where the performance of aqueous epoxy systems is not only adequate but can be even superior to conventional systems, e.g., adhesion to wet concrete. The most important applications for water-based epoxy systems today are coatings on concrete, primers for metal, and epoxy cement concrete (ECC).

However, one of the problems with low-VOC waterborne epoxy and hardener dispersions is that the freeze/thaw stability of these dispersions is often poor since common anti-freeze solvents are VOCs. We have found a surfactant system that imparts good freeze/thaw stability to epoxy dispersions. In addition, and perhaps more importantly, the stability and pot life of the dispersions are improved, often with improved cure times. Gloss and water resistance of the cured coatings were checked and are good. Formulations with good combinations of pot life, cure time, and freeze/thaw stability will be shared along with the presumed mechanisms for the excellent performance observed.