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topic 0975

Powder Paint Visible Emissions from Bake Oven Exhaust


We are experiencing periodic visible emissions from the bake oven in a polyester urethane powder paint operation. There is also a brown (creosote-like) substance on the exit of the oven,and on the bottom of the raincap. We believe that it is caprolactam from the blocking agent in the paint. Wondering if anyone is having or has had a problem with this? We are considering changing to a TGIC blocker, but are concerned about health issues associated with it. Any advice would be greatly appreciated.



The e-caprolactam blocking agent present in most urethane polyester coating powders is released to some extent during the cure cycle. The two conditions you describe are common to this type of powder.

If you are experiencing visible emissions within your building and excessive residue in the oven, then it is likely that your oven exhaust rate is lower than it ought to be for the volume of coating in the oven.

One potential solution is to increase the oven exhaust rate while maintaining adequate cure temperature. Another is to relate the problem to coated part density and then avoid the loading that causes the problem.

Working with your powder supplier, you should be able to easily and safely use TGIC polyesters if that is your desire.

Jeff Hagerlin
paint supplier - Houston, Texas


Our firm is interested in purchasing of the polyester powder paint.

Andrey Leschenko
- Ukraine


Yes, it is quite clear that when you use polyester urethane powder that there is a quite likely chance of residue in the exhaust system as well as anywhere else you might expose the fumes to during the cure. It is our best solution to periodically raise the oven temperature above the flashpoint of this substance and clean it that way. Of course we do have many exhaust scrubbers and filters to catch all of this extremely toxic substance. I am surprised you have not had serious illness from what you have described. We noticed that before we had these safeguards and exhaust processors, we found quite a few church mice dead and mummified! Not even the fly eggs survived amazingly. It is to our own luck that our process was confined to one set of rooms that did not contain humans during the cure process.

John Q. Dinkleberry
- Yreka, California, USA

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