Effect of different fire retardants on birch plywood properties
2016
Bekhta Pavlo | Bryn Olesya | Sedliačik Ján | Novák Igor
The feasibility of applying conventional flame retardants usually used to improve fire behaviour of solid wood was evaluated in this study for the production of fire-resistant plywood panels. For making plywood the birch (Betula verrucosa Ehrh.) veneer and commercial phenol-formaldehyde glue resin were used. Five different standardized fire-retardants were chosen for veneer impregnation. Firstly, veneer sheets were treated by immersion in 20% aqueous solution of each fire-retardant. Diffusive and capillary impregnation was evaluated to select the most effective treatment of veneer. Absorption of impregnation solution in veneers was determined. Afterwards, five-layer plywood panels were prepared from impregnated veneers in laboratory press at the following pressing parameters: pressure of 2.0 MPa, temperature of 130°C, time of 10 min and glue spread of 120 g/m2. Shear strength and fire resistance of plywood were determined. It was found that diffusive impregnation of moist veneer, in comparison with capillary impregnation of dry veneer, is characterized by the less salting-out of fire-retardants on the veneer surface and their more homogeneous distribution in middle of veneer. It was proved that conventional fire-retardants for solid wood can be used for plywood and also allow re-classification of plywood from the group of increased flammability materials to the group of hard inflammable materials.
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