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Ask the Expert Question-and-Answer Archive by Ron Joseph March, 2005 Solvent Entrapment on Paint Coatings Q. I am using a polyurethane coating HUMISEAL 1A33 and then drying it an IR Oven. Is this recommended as I believe the solvent gets trapped in the coating and it can never completely cure as there would be no oxygen. Would an acrylic coating be better? A. If you place the polyurethane or ANY other coating into an oven too soon, the solvents can become entrapped in the paint coating film. In some cases the solvents can remain in the coating for years and eventually cause blistering. Polyurethanes and epoxies are more prone to this than single component paint coatings because they cross link when they cure. You CAN cure a polyurethane or epoxy in an IR or convection oven, but first wait for several minutes to allow the solvents to flash off at room or even at a slightly elevated temperature. You will need to experiment with the flash-off time because it is affected by the film thickness of the coating. By the way, the same considerations apply to acrylic coatings, but they are less sensitive to solvent entrapment because they are single component coatings. Wait for most of the solvents to flash off! Oxygen has nothing to do with this. Best wishes,
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