Seven B.C. species, namely, interior Douglas fir, coastal second growth Douglas fir, western larch, lodgepole pine, western white spruce, trembling aspen and white birch were evaluated for their laminating properties using different adhesive formulations and pressing conditions.
Using optimized gluing and pressing conditions, six of the B.C. species showed excellent bond quality when laminating with radio-frequency (RF) heating and either cross-linked polyvinyl acetate (PVAC) or phenol-resorcinol-formaldehyde (PRF) adhesive. These laminates easily passed the shear block wood failure requirement in the ASTM-D-2559 standard and the delamination requirement in the ASTM-D-1101 standard. Because white birch which has a high density showed the highest block shear strengths for the optimum PRF adhesive formulation, this species showed the lowest average percent wood failure of the seven B.C. species and did not meet the ASTM-D-2559 wood failure requirement of 75%.
Using conventional platen pressing at 20 or 25°C, laminates were prepared with different PRF adhesive formulations and the seven B.C. species. Using an optimized PRF adhesive formulation, the laminates for the seven BC species met the above ASTM standard requirements for wood failure and delamination.
Overall, the percent wood failure was higher for the laminates made at 25°C indicating more resin cure. Hence, for laminates made with the optimum PRF formulation, PRF-C, the average percent wood failure for western larch at 20°C was 78% compared to 98% at 25°C.
Laminated products - Manufacture - British Columbia