Effects of acidity of the particles and amount of hardener on the physical and mechanical properties of particleboard composite bonded with urea formaldehyde

In this study, the effects of amount of hardener on some of the physical and mechanical properties of three-layer particleboard were determined. Variable factor was hardener use amount (0.40%, 0.60%, 0.80%, 1.0% and 1.5% for outer layers, and 1.5%, 2%, 2.5%, 3.0% and 3.5% for core layer, based on the solid weight of the adhesive). Manufacturing parameters such as type of adhesive (urea formaldehyde), hydrophobic substance (paraffin), hardener (ammonium sulphate), target board density (0.635 g/cm3), pressure (25 kg/cm2), press temperature (225 °C), press time (100 s) were held constant. The panels were tested for their mechanical properties including modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB) and physical property (thickness swelling (TS)) according to the procedures defined by European Union (EN) standard. While the mechanical and physical properties were improved as amount of hardener increased from 0.40% to 1% for outer layers and 1.5% to 3% for core layer, increasing amount of hardener to 1.5% for outer layers and 3.5% for core layer negatively affected these properties. Increasing amount of hardener from 0.8% to 1.0% for outer layers and 2.5% to 3.0% for core layer did not significantly affect all of the properties of particleboard panels.