2. Materials and methods
2.1. Manufacture of particleboards
Pine (Pinus brutia Ten.) wood (90 wt%), beech (Fagus orientalis Lipsky) wood (5 wt%) and poplar (Populus tremula L.) wood (5 wt%) particles were used in the manufacture of particleboards. The particleboards were produced in a commercial particleboard plant (Starwood Forest Products Company) in Inegol, Turkey. First the wood particles were classified using a horizontal screen shaker. The particles remained between 3 and 1.5 mm sieves and between 1.5 and 0.5 mm sieves were utilized in the core and surface layers of the particleboards, respectively. The wood particles were dried at 220 °C temperature to reach target moisture content 1%. E2 grade commercial UF resin having 65% solid content at 11% and 9% adhesive levels based on the oven-dry weight were used for the outer and core layers of particleboard, respectively.