Impact of Resin Content on Swelling Pressure of Three Layer Perticleboard Bonded with Urea-Formaldehyde Adhesive

When particleboards are exposed to water or moist environment, they tend to swell and expand in all directions. The degree of swelling or expansion depends on the type of adhesive used, its share, and the time of exposure and pressure used at hot pressing. The expansion of particleboard, exposed to water or high moisture content, is accompanied by swelling and/or expansion pressure. The purpose of this paper is to present the impact of adhesive share on thickness swelling and swelling pressure of three layer particleboard bonded with ureaformaldehyde adhesive. The resin content was altered in both layers; in core layer it was between 6 and 9 %, and in surface layer between 11 and 13 %. Thickness swelling and swelling pressure were determined with 24-hour immersion test. For the swelling pressure measurement, special force gauge device was used. The biggest changes in swelling and pressure were observed when the resin content was changed in core layer. The fastest change in swelling and swelling pressure was observed in the fi rst few hours after immersion in water.