Reducing formaldehyde emission from wood-based panels by modification of UF and MUF resins with condensates obtained from kiln-drying of wood

Liquid condensates collected during drying of lumber, sawdust or wood powder are usually discarded. The objective of this study was to investigate the potential utilization of such condensates from oak, beech and walnut, focusing on those obtained in a 7.8 MHz vacuum dryer. The condensate was replaced with the deionized water (5%) in the production of urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) resins in the reactor. The technical properties of the resins and chemical properties of the liquid condensates were determined. Particleboards (PB) and middle density fiberboards (MDF) were produced from the control and modified resins. The technical properties of both modified resins were between the limit values of commercial UF and MUF resins used in the wood-based panel industry. The formaldehyde (F) emission from PB and MDF decreased significantly by incorporation of the condensates into the UF and MUF resins.