Effect of glutaraldehyde on water related properties of solid wood

Scots pine sapwood was treated with various concentrations of glutaraldehyde (GA) and magnesium chloride as a catalyst in aqueous solutions. The weight percent gains (WPGs) attained after leaching were 1.0%, 8.6%, 13.7%, and 21.9%, respectively. The treatments reduced the equilibrium moisture content at 90% RH up to 30% compared with the untreated controls. Capillary water uptake of wood was also restrained by GA treatment (8.6% WPG) resulting in water reduction effectiveness of approximately 50% in both radial and tangential direction after 244 h. Wood blocks treated to the highest WPG (22%) attained 70% anti-swelling efficiency (ASE). High ASE values were caused by cell wall bulking through incorporation of GA in the cell wall and as a result of reduction of the maximum degree of swelling in water, i.e., through crosslinking of cell wall polymers. During 10 water submersion and drying cycles, untreated and GA treated specimens displayed equal weight losses indicating that mainly wood constituents were washed out. These cyclic water submersion tests also caused approximately 10% reduction in ASE in samples treated to higher WPG. Magnesium chloride as a catalyst for the reaction of GA imparts wood similar water related properties as sulphur dioxide catalysis of GA treatment, but the application of MgCl2 is much easier to perform in practice.