We observed the influence of cold pre-pressing on properties of heavily burnable plywood. Beech veneer was impregnated with Borax and Boric acid water solutions. Then it was dried again and veneer boards, glued with melamine-urea-formaldehyde glue, were produced. In the manufacture of plywood, 2 different periods of cold pre-pressing time (9.5 min and 29.5 min) were compared. To determine thickness loss, density and moisture content, bonding quality, bending strength and modulus of elasticity plywood specimens were prepared. Based on the results of testing of plywood mechanical properties, the impact of cold pre-pressing on the quality of adhesion was evaluated. We found out that we could influence mechanical properties of heavily burnable plywood already with 9.5 min cold pre-pressing, because the shear strength increased for 5.7 % regarding to the non-cold pre-pressed plywood. Due to cold pre-pressing of artificially aged plywood boards, the shear strength increased for 8.3 %. The bending strength in the longitudinal direction increased for 13.3 %, in transverse for 18.3 %. Modulus of elasticity in the longitudinal direction increased for 6 %, in the transverse for 8.3 %. At longer (29.5 min) cold pre-pressing time, the shear strength of adhesive bond of soaked specimens decreased for 8.6 %, compared to that of non-cold pre-pressing specimens. Strength of artificially aged specimens was 12.5 % lower. After 29.5 minutes, the cold pre-pressing of the bending strength increased, but the increase was less than at 9.5 minutes long cold pre-pressing. At 29.5 minutes long cold pre-pressing, the modulus of elasticity was 3.1 % higher in longitudinal direction, while in the transverse direction it decreased for 1.3 %.
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