The effect of the use of Dimethyloldihydroxyethyleneurea (DMDHEU) chemical in MDF production on the properties of the board

Abstract

Since wood-based boards are hydrophilic material, they should be treated with chemical substance that gives hydrofob properties during production. In this study, it was aimed to investigate the effects of board density and the different addition way of the chemical during board production which by using dimethyloldihidoxythyleneurea (DMDHEU) that is a cross-binding water-repellent resin chemical on the mechanical and physical properties of the board. Melamine Urea Formaldehyde glue (1.16 mol, 5% melamine added), ammonium chloride as hardener and 2.2% DMDHEU chemical were used in the production of the board. The DMDHEU chemical was added to the fiber in three different ways during the gluing process: before gluing (TÖ), after gluing (TS) and together with glue (TB). İt was determined that the water absorption and swelling values of the boards produced with the addition of DMDHEU chemical were lower than the control board. The lowest values in the water absorption and swelling values of the boards produced with the addition of the chemical TS were obtained as 26.27% and 13.3%, respectively. The water absorption value of the control board was determined as 35.84% and the swelling value as 16.8%. It has been determined that with the increase in the density values of the produced boards, the water uptake and swelling values tend to decrease. Although improvements were obtained in the mechanical properties of the boards with the increase of the board density, the best results has been obtained in the addition of the chemical to TS, especially in the bending (43.78 N/mm2) and tensile strength values (1.78 N/mm2).