The isocyanate hardener in these powders is capped with a blocking agent, often caprolactam, that releases at oven temperature and frees the isocyanate to react. Urethanes give excellent flow, thin smooth films around 1.5 to 2.5 mils, and good chemical and weather resistance. The released blocking agent can smoke and build up as residue in ovens and exhaust stacks, and the films are prone to gassing at heavy builds.
Oven stack's dripping again, that's the caprolactam from the urethane run last week.
Also heard as
- polyurethane powder
- urethane
Related terms
Polyester powder
Powder based on polyester resin, the standard choice for outdoor parts because it holds color and gloss in sunlight.
Crosslinker
The hardener in a thermoset powder that reacts with the resin to tie it into a network.
Flow
How far and how smoothly melted powder spreads out before it gels, which sets surface smoothness.
Film build
The thickness of the cured coating, usually given in mils or microns.