Dynamic moisture sorption and formaldehyde emission behavior of three kinds of wood-based panels

Three kinds of wood-based panels, namely medium density fibreboard (MDF), particleboard, and plywood with the poplar wood flour control were subjected to cyclic environmental conditions with the relative humidity (RH) changing sinusoidally between 45% and 75% at 25 °C. The moisture content (MC) was measured based on the weight percent gains, and the formaldehyde concentration was tested in the 1 m3 chamber at different RH (45, 60, and 75%). The results showed the MC of all the samples changed sinusoidally with RH, but time delays to reach their maximum MC at each step were observed. The amplitudes of MC at each cycle decreased in the order of poplar wood > plywood > particleboard > MDF, which is associated with their chemical components and adhesives contents. The formaldehyde emission was closely related to the RH. With increasing RH, the formaldehyde concentration increased. The formaldehyde concentration of particleboard was the highest, followed by MDF. Plywood had the lowest formaldehyde concentration of all.