2009 Summer Gluing Tips

The summer months can be described as hot and humid in most places. Heat and humidity will have an effect on the setting rate and handling characteristics of wood adhesives as well.

• PVA adhesives will generally cure more quickly in the summer months. While this is usually not a problem in most assembly and edge-gluing operations, it can be a source of problems in laminating and veneering operations. Make sure that the closed assembly time is not exceeded by looking at the squeeze-out on the bottom panel. If there is little or no squeeze-out, increase the glue spread or reduce the number of panels in each press load.

• Moisture content in kiln-dried wood will rise during periods of high humidity. If the average ambient humidity is above 40%, the moisture content of the wood will be in excess of eight percent. This can be a source of gluing problems, particularly with radio-frequency gluing. Also, high moisture content wood will slow down the rate of cure for PVA adhesives.

• Polyurethane (PUR) Hot Melts will generally set up more slowly due to the higher temperature. Lowering the temperature of the gun or coater 10-20°F will often compensate for higher plant temperatures. Franklin also has products that differ on open and set times, but are similar in viscosity and strength.

• Higher humidity levels can reduce the useable life of melted adhesive in roll-coaters and in heated reservoirs found in laminating and 2K machines. Avoid keeping melted adhesive exposed to the air for extended periods.