Effects of a variable glue application rate strategy on bond quality and resin consumption in the manufacture of southern pine plywood

The use of glue application rate to control gluebond formation and hence plywood quality has been long recognized by plywood managers. The thrust of research in the past has been to modify the resin and/or glue mix to tolerate the broad range of material and manufacturing conditions that affect bonding. The objective of this study was to investigate the use of glue application rate to influence bond formation resulting in improved bond quality and reduced resin consumption. Test panels were manufactured in a full factorial experimental design with three levels of veneer roughness, three levels of assembly time, three levels of veneer moisture content, two levels of veneer temperature, and two types of glue application rate strategies. With each combination replicated, a total of 216 test panels were made and tested using the standard vacuum/pressure soak test. The results show that variable application rate strategy (VARS) yielded the same average wood failure as the constant application rate strategy (CARS) while using 11.3 percent less glue mix. CARS performed better than VARS when conditions of smooth veneer and dryout existed. VARS performed slightly better than CARS when conditions of overpenetration existed. With some adjustments to the VARS schedule, its lack of performance under conditions of dryout may be improved to a point to warrant its use in plywood production.

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