Production of polymer matrix composite particleboard from walnut shell and improvement of its requirements

The purpose of this study was to produce urea–formaldehyde based composite particleboard from walnut shell and improve its requirements such as non-flammability, eradication of fungal and insect attack, and water resistance features by using fly ash and phenol–formaldehyde. For this purpose, under laboratory conditions, parameters affecting polymer composite particleboard from walnut shell and urea–formaldehyde were specified to be urea–formaldehyde ratio, reaction temperature, and reaction period, and the effect of these parameters on hardness was investigated. The optimization results showed that maximum bending strength was 3.8 N/mm2, at urea–formaldehyde ratio of 1.0, reaction temperature of 70 °C, reaction time of 25 min, walnut shell filler/urea–formaldehyde resin of 3 and mean particle size of 0.12 mm. As a result of burning tests, although the maximum flame temperature of composite particle board without fly ash was 535 °C, it was 299 °C with fly ash of 15% (w/w) according to the filler. Water absorption and increasing in the thickness exponentially decreased with increasing phenol–formaldehyde/urea–formaldehyde ratio.