Recent advances in wood modification through the use of maleic anhydride and sodium hypophosphite

Maleic anhydride (MA) is a cyclic anhydride capable of forming an ester bond with wood constituents, providing enhanced dimensional stability and fungal resistance of wood. However, the weight gain through treatment was lost during wet-dry cycle, which indicates that the ester bonds in maleated wood is susceptible to hydrolysis. This study focuses on improving the stability of the maleated product through the use of sodium hypophosphite. Studies have shown the combined treatment resulted in improved anti-swelling efficiency (ASE), lower weight loss and smaller saturated volumes than untreated or specimens treated with maleic anhydride along. In order to better understand the relationship between the modified wood and water, low-field nuclear magnetic resonance (LFNMR) spectroscopy was used to determine the influence of moisture in wood. The modification process resulted in a weak wood–water interaction using LFNMR, suggesting an increased T2 relaxation time of capillary water. However, the weak wood–water interaction did not seem to be related to the accessible hydroxyl groups because the modification reaction resulted in a similar number of hydroxyl groups as present in unmodified wood. This finding would appear to agree with the concept of MA modification resulting in the “ring opening” of the anhydride, creating a carboxylic acid group for each hydroxyl group modified within the wood. Funder: Northern European network for wood science and engineering (WSE); Advanced research supporting the forestry and wood-processing sector’s adaptation to global change and the 4th industrial revolution, OP RDE, (CZ.02.1.01/0.0/0.0/16_019/0000803)