Two-Component Waterborne Polyurethane Coatings
The field of polyurethane chemistry may be 60 years old, but regular advances
keep it vital and interesting. Reactive two-component polyurethane
coatings historically have been stringently protected from water,
but in the early 1990s it was shown that such reactive systems could
actually be formulated using water as the carrier and still produce
films with outstanding appearance and barrier properties.
The introduction of two-component waterborne polyurethane systems
is providing a means to formulate ultra-low volatile organic compounds
(VOC) and hazardous air pollutants (HAPs) systems, with performance
properties that closely match those of two-component solventborne
polyurethanes. A two-component waterborne polyurethane system utilizes
hydroxyl-functional coreactants, commonly polyesters or polyacrylates,
that are stable dispersions in water. Ideally, the polyol (component
I) is formulated with all flow aids, thickeners, pigments and water
incorporated into the mixture. A polyisocyanate (component II) is
then mixed into component I prior to application, forming a stable
dispersion. This is then applied to a substrate by conventional methods
and can be cured under ambient conditions or force dried under a variety
of bake conditions.
For additional information about two-component waterborne polyurethane coatings, please visit our literature request section.