Walnut/almond shells were first cleaned of dirt and impurities,
and then chipped by a knife ring flaker. Next the chipped shells and
wood particles were classified in laboratory shaker. Particles that
remained between 3–1.5 mmsieve and 1.5–0.8 mmsievewere uti-lized in the core and outer layers, respectively. Particles were oven
dried at 100 ± 3C to reach the target moisture content (3%). Urea
formaldehyde (UF) resin at 9% and 11% levels (based on oven dry
weight of the particles) was used for the core and outer layers
respectively. One-percent ammonium chloride (NH4Cl) was also
added to the resin as a hardener. Particleboard panels were manu-factured using standardized procedures that simulated industrial
production at the laboratory. The particles were placed in a drum
blender and sprayed with urea formaldehyde and ammonium
chloride for 5 min to obtain a homogenized mixture. The shelling
ratio was 35%. The glued particles then were pressed into panel
mat using a laboratory scale hydraulic hot press. Thickness of
panels was controlled by stop bars and panels target density was
0.7 g/cm
3
. Three panels were produced for each group. The exper-imental design is shown in Table 2. The dimensions of the pro-duced particleboards were 42421.6 cm. The produced
particleboards conditioned at 20C and 65% relative humidity to
reach moisture content of about 12% before trimming to final
dimension of 40401.6 cm. The panel production parameters
were also displayed inTable 3.