Supplementation of Natural Tannins as an Alternative to Formaldehyde in Urea and Melamine Formaldehyde Resins used in MDF Production

The aim of this study was to evaluate some mechanical and physical properties of medium density fiberboards (MDF) made from different adhesive types. Five panel types were made from mixtures of tannin (T) to urea formaldehyde (UF) and tannin to melamine formaldehyde (MF), TUF10%, TUF20%, MF, TMF10% and TMF20%, respectively. Besides, the effect of press temperatures (170 and 180 degrees C) on the curing of the formulations was studied. Some mechanical properties (modulus of rupture, modulus of elasticity and internal bond strength), physical properties (thickness swelling and water absorption) and formaldehyde emission of the resulting panels were determined. The incorporation of tannin decreases the formaldehyde emission of the panels. However, flexural properties and internal bond strength decreased with increasing tannin ratio. The results indicated that panels can be manufactured using tannin up to 10% in UF resin without falling below the minimum EN Standard requirements of mechanical properties for general purpose MDF panels.