Catalyzed Polyurethane Adhesion Problems

      Quick hints on why a calatyzed poly topcoat might be peeling away from the previous coat. January 27, 2008

We use a catalyzed polyurethane finish on our doors and panels made of sapele lumber and veneer. We build up a clear base which fills the pores and then we use a 50 degree topcoat from the same manufacturer. We have encountered some cloudiness when we apply the top coat and in some instances peeling of the top coat right off in large parts. Any suggestions?

Forum Responses
(Finishing Forum)
From contributor G:
The finishing schedule would be useful to troubleshoot that.

From contributor R:
Some post-cat polyurethanes like to be completed in one day. Even though you might sand the previous coat prior to applying the next coat, you could have an adhesion problem. Another thing for you to consider is that most polyurethanes really like heat! Any moisture in the air or in the air lines can really cause problems too.

From contributor J:
What exactly are you using as your clear base? And what is your sanding procedure? Are you using a quick wood type flatter sander? Sometimes coatings contain a wax and can cause adhesion issues when flatter type sanders are used. Not much sanding really takes place, but the friction from the bristles cause the wax to melt and form a barrier which can cause intercoat adhesion problems.

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