Cure and Recoat Mechanism of 2K Polyurethane Topcoats

Two component urethane coatings are noted for their ability to low temperature cure. As a class, once fully cured, they are not generally noted for recoatability without surface treatment. However, with some understanding of the cure mechanism, attention to formulation variables and control of the cure process conditions, the recoatability window of 2K urethanes can sometimes be significantly widened.

The role of humidity in the cure process is perhaps of more significance than many people once thought. The benefit of introduction of humidity into the “bake” oven during winter dry conditions is clearly demonstrated in a case history for one system for a major 2K urethane finisher of large exterior plastic components.