1K & 2K Systems
Polyurethanes based on aliphatic polyisocyanates are renowned for their outstanding
properties and especially for their exceptional resistance to weathering and chemical attack. Two main categories of
polyurethane systems can be distinguished: two-component (or 2K) and heat-activated,
one-component (or 1K).
2K POLYURETHANE COATINGS
Two-component systems consist of a polyisocyanate and a polyol that are mixed just
prior to application and cure at room temperature. In volume terms, this
family accounts for over half of all urethane coatings sold in the world.
The crosslinking reaction (-NCO + -OH) occurs on the substrate at room temperature,
but sometimes, stoving 30 min at 60°C or 80°C is used to speed up drying
(for productivity reasons) .
Therefore, 2K polyurethane coatings are used :
- on substrates sensitive to heat (plastics, wood, cars....),
- on objects too big to be stoved (trains, airplanes, bridges...).
1K POLYURETHANE COATINGS
One-component PUs are similar materials to the previous one, except that a blocked
isocyanate is used to provide a storage stable one-pack formulations containing
the polyol. After application of the coating on the substrate and during
stoving at elevated temperature, the isocyanate is de-blocked and then it reacts
with the polyol to form the PU network. This includes powder coats, which consume
now over 10% of all urethane in paints