The Effect of coating with melamine impregnated papers on the technical properties of particleboard

The Effect of Coating with Melamine impregnated Papers on the Technical Properties of Particleboard SUMMARY Specific properties of the boards used in this study were as follows: 280x210 cm; 18 and 12 mm in thicknes; 0.70 gr/cm3 in specific gravity. Half of these boards were coated with melamine impregnated papers. In the production of the boards, urea formaldehyde which was 9.5 and 8.5 % of the oven dry weight of the chips was used as adhesive in the outer and middle layers respectively; as the hardener, amonium chloride which was 2.5 % of the hard adhesive was used in the middle layer; as the hydrophobic substance paraffin which was 5 % of the hard adhesive was used in the outer layer. In the production of the 18 mm particleboards, press time, press temparature and pressure were 145 sec, 200 °C and 34.5 kg/cm2 respectively. In the case of 12 mm particleboards these values were; 130 sec, 200 ° C and 34.5 kg/cm2 for the press time, press temperature and pressure, respectively. While coating the boards; press temperature, press time and pressure were maintained at 205-207 °C, 35 sec. and 21 kg/cm2, respectively. Boards were conditioned in a conditioning room for three weeks at 18-22 ° C and 60-70 % relative humudity until all the boards reached an equilibrium moisture content. After that, boards were recut at the specified dimensions and were replaced in the conditioning room. The following was recorded durind the experiments: moisture content, water absorbtion and thickness swelling at 2 and 24 hours after soaking in the water, specific gravity, bending strength, modulus of elasticity, bonding strength, screw holding and the amount of formaldehyde emission from boards stored, in turn, for one day, one week, one month and three months. As a result, it was concluded that coating with melamine impregnated papers improved the physical and mechanical properties of particleboards and that formaldehyde emission was remarkedly reduced. In addition, except for the bending strength, equilibrium moisture content and formaldehyde emission, the board thickness was found to be effective on all other physical and mechanical properties of particleboards. Key Words: Formaldehyde, melamine impregnated papers, particleboard. vm