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The suitability of continuous laminated veneer lumber production to some Canadian wood species Afolayan, Ademola Adeniyi

Abstract

Laminated veneer lumber was made by gluing six layers of 1/4-inch veneer assembled with grain directions parallel and all the tight veneer surfaces outward. A specially modified phenol-formaldehyde plywood resin was used. Shear strength and wood failure of specimens tested dry, and after accelerated aging, were used to evaluate bond quality. Limited samples of broadleaf maple laminated veneer lumber were used to demonstrate that, with central glueline just reaching 240°F before opening the press, adequate bonds were formed. These were not significantly different from those produced with a central glueline temperature reaching 300°F. Tests of specimens from small panels of broadleaf maple, black cottonwood, and sugar maple showed that a gluespread of at least 42.5 pounds per thousand square feet of single glueline (42.5 lb/MSGL) was required. At this spread, a central glueline temperature of 240°F and platen temperature of 350°F, adequate bond quality was produced at platen pressures of 200 psi, 100 psi and 275 psi for broadleaf maple, black cottonwood and sugar maple, respectively. Based on the press schedules developed with the small panels, black cottonwood, sugar maple, and white spruce, continuous laminated veneer lumber boards were manufactured, using the process described by Bohlen in 1972. Only the white spruce boards produced adequate bonds. Those of black cottonwood and sugar maple failed due to dry-out of glue adjacent to the platens. Although suitable pressing conditions were worked out for single-pressed boards, irrespective of wood species, the glue would need further modification for the hardwoods studied to be used for continuously produced laminated veneer lumber.

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