Curing Temps and Times

Question:

I have an application where I need to test a bonded joint that is buried in a powder coated assembly. I need to pre-condition the part at the curing temperature for the expected curing time to ensure the adhesive is exposed to what it could see in processing. The tech sheet for the powder coating calls for a typical cure of 15 min at 275°F. My question is, will the parts be subjected to the 275°F temp for 15 min total or will they be held in the oven for 15 minutes once the parts get up to the oven temperature? The second scenario would lengthen my overall exposure time by the heating time to bring the part up to temp. S. D.

Answer:

The cure time listed on your powder formulator’s data sheet is the time at metal temperature. This means that the part will be in the oven longer than this time to achieve this temperature. A simple formula explains this: Oven Dwell Time = Bring-Up Time + Powder Cure Time. However, remember that the cure time at the temperature given by your powder formulator is only one point on the entire cure time/temperature curve. There are other times that correspond to other temperatures on this curve. Any combination of these times and temperatures representing a point on this cure curve will achieve full cure of the powder coating. Therefore, you can select a different temperature and corresponding cure time to accommodate your bonding adhesive and still cure the powder coating properly. Just be sure to stay on the line on the curve.