Why does plywood become delaminated?
January 3, 2013 | 9:00 am CST
Q: We have been experiencing some delamination of our plywood. We have recently switched to a new source of supply. With the rejects we are getting, any price savings is gone. Why does delam occur?
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A: Are you talking about delamination within the plywood or delamination of the decorative veneer from the plywood core? I will answer both possibilities.
Delamination in plywood occurs when the glue holding the two pieces of veneer fails. A good glue bond can tolerate many hundreds of pounds of stress per square inch, so failure, even if the panel is slightly mistreated, is normally not likely to happen. In fact, those plywood panels with the APA quality symbol will be guaranteed against delamination.
All delamination occurs because something is not being done correctly at the plywood manufacturing mill. The exceptions would be for plywood that is exposed to extreme heat (which melts the glue) or quite a bit of wetting (which may dissolve the glue or may promote decay) after manufacturing...a rare event in furniture and cabinets.
A few examples of what might go wrong in manufacturing include having veneer too wet, so that the heat from the press creates steam that blows the board apart; having the veneer too dry so that the liquid in the adhesive is adsorbed before the pressure is applied (called pre-cure); inadequate or uneven pressure when gluing so that the veneers do not make intimate contact when gluing; poor glue spreading rate so some areas of the veneer do not have any glue; and using the wrong or out-dated adhesive.
In short, delamination within a plywood panel is seldom, if ever, a problem caused by the furniture manufacturer.
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