Some Technological Properties of Plywood after Fire Retardant Treatment in Different Concentrations

The treatment with fire retardant chemicals is the most effective process to protect wood and wood based products from fire. Therefore, use of fire retardant chemicals has been increased. However, the fire retardant chemicals have an effect on other physical, mechanical and some technological properties of the materials treated with them. In this study the effect of various fire retardant chemicals in different concentrations on the technological properties of plywood were examined. Poplar (Populus deltoides) and scots pine (Pinus sylvestris L.) were used as wood species; zinc borate, monoammonium phosphate (MAP) and ammonium sulfate were used as fire retardant chemicals and UF resin was used as adhesive. The veneer sheets were treated by immersion and three different concentrations, such as 5%, 7% and 10% aqueous solutions were selected. Mechanical properties of plywood panels, such as the shear strength, bending strength and the modulus of elasticity were determined according to EN 314-1, EN 310, respectively. The surface roughness of the veneer sheets was determined according to DIN 4768 standard. As a result of this study, it was found that all the mechanical strength values of panels produced by using the veneers treated with fire retardant chemicals were lower than those of control panels. With the increasing of the solution concentration their values decreased while the surface roughness values increased