Q: Is moisture an important measurement in the manufacturing of powders used in coating? If so, how is water measured? Also, does water affect polyurethane powder coating curing mechanism?
A: Believe it or not, powder coatings can tolerate a fair amount of moisture (up to 0.5% or more). Completely dry powders in a very low-humidity environment (< 15% relative humidity) exhibit electrostatic charging problems. Think of the charge picked up by dragging your feet (with socks) across carpeting on a very dry day in a cold winter. Excess static charge abounds. So, a little bit of moisture is better than none.
However, high levels of moisture (>1.0%) cause clumping issues and poor fluidization. These phenomena create handling and application problems.
As for moisture interfering with cure in an isocyanate-cured polyester powder, this is not an issue since there is negligible free NCO available because a blocking agent is present.