Gluability of Southern Pine Veneer Dried At High Temperatures

The study reported was designed to provide information on the effects of maximum surface temperature and extractives on gluability of southern pine veneer dried in an oven maintained at 500?F. The results are analyzed by standard statistical methods. The veneer was peeled at a plywood mill which preheated the bolts prior to cutting. It was taken from the sapwood of a single bolt, 16 inches in diameter and 8 feet long,which appeared to be free from defects. Green thickness of the veneer averaged 0.132 inch, The average density of each sheet was 0.47 gram per cubic centimeter. Extraction was done in an aluminum tank fitted with water-cooled condensers and heated in a steam bath. The veneers were dried individually in an electrically heated cross-circulation oven maintained at 500?F.; drying time for each piece was determined by surface temperature. In the presence of extractives, the gluability of southern pine veneer deteriorated when the veneer surface was heated to 500?F. Scorched appearance of veneer was not a direct result of high dryer temperatures, but occurred only when the veneer surfaces reached high temperatures. It appears feasible to dry veneer at temperatures in excess of 500?F. The danger of over-drying could be reduced by using a two-stage dryer. High temperatures would be applied in the first stage, where most of the water would be removed. The second stage would operate at a more moderate temperature to prevent excessive veneer temperatures.

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