Finger- and Edge-Jointing Softwood Lumber Using the Preheating Method and Emulsion Polymer Isocyanate Glue

A preheating method was used to prepare finger- and edge-joints from kiln-dried spruce-pine-fir lumber. An emulsion polymer isocyanate glue was used as the binder. All the edge-joints were prepared using a 10-minute heating schedule at 150?C. The edge pressure and top platen temperature were varied from 50 to 200 psi and 20? to 90?C, respectively. The finger joints were prepared using two heating. schedules, 10 and 15 minutes at 150?C. Both the edge and finger joints exhibited excellent bond quality for all the above bonding conditions. The edge joints averaged over 1,000 psi in shear strength and over 80 percent in wood failure. The finger joints were tested in bending and averaged over 6,000 psi in modulus of rupture and 90 percent in wood failure. The edge and finger joints showed very low delamination values, with most test specimens showing no delamination, indicating glue-wood bonds of very good durability.

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