Optimization of reaction parameters and characterization of glyoxal-treated poplar sapwood

Abstract

Glyoxal as a non-formaldehyde cross-linking agent was employed with ammonium persulfate as a novel catalyst to improve the dimensional stability and water resistance of poplar sapwood. The effects of various cross-linking parameters (e.g., glyoxal concentration, curing temperature, glycol-to-glyoxal molar ratio and catalyst concentration) on the properties of wood were investigated, and the parameters were optimized. In comparison with the unmodified wood, the glyoxal-modified wood exhibited improved dimensional stability and reduced water uptake. Moreover, the addition of glycol further strengthened the dimensional stability and anti-leaching ability. Modified wood was characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM) and contact angle instrument. IR indicated that the network structure was formed between the agent itself or cross-linking between wood components and glyoxal. SEM revealed the precipitation and filling effect of the cured glyoxal in the cell wall. Contact angle measurement further confirmed the improved hydrophobicity of wood after modification. All the results suggested that the improved dimensional stability and water resistance of the treated wood could attribute to both bulking effect and cross-linking reaction or network structure formed. However, it is not clear whether network structure by glyoxal itself or the cross-linking between the glyoxal and wood components is formed in wood.