2K polyurethane coatings are supplied with the polyol, pigments, solvents
and additives in one pack and the isocyanate in a second pack. Once these 2 components
are mixed, the crosslinking reaction begins, causing an increase in paint viscosity
in the case of solvent-based systems.
Spraying, rolling or brushing the coating is possible until the viscosity
of the system becomes too high. It is an advantage for applicators to have a pot-life
long enough to have sufficient flexibility in their work.
In 2K waterborne formulations, pot-life has to be measured by decrease of properties
(such as gloss and chemical resistance), since viscosity increase alone is not a
Formulators often have to choose between a long pot-life and a short drying time. Improvement of aliphatic polyisocyanates
now offers the possibility to get both performances.