Thickness Loss in Hot-Pressed Plywood

Thickness losses in plywood panels during hot-pressing are well known but recent trends toward gluing at higher veneer moisture content (MC) and press temperature result in losses much greater than previously expected. This study of 5/8-inch plywood made from conventionally dried and platen-dried veneer (Douglas-fir, southern yellow pine, hem-fir) examined the effect of veneer MC (1 and 6%), press temperature (270? to 330?F), press pressure (single and multiple-step cycles), and wetting of hot panels on percent thickness loss. The greatest thickness losses were with veneer at 6 percent MC, press temperature of 330?F, and steady pressure at 200 psi. These losses can be minimized by reducing pressure at press closure or during the press cycle. Panels wetted immediately after hot-pressing recovered 1 percent of thickness, regardless of veneer and pressing conditions.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member