Modification of poplar wood with glucose crosslinked with citric acid and 1,3-dimethylol-4,5-dihydroxy ethyleneurea

Poplar wood (Populus adenopoda Maxim) has been modified by glucose (GLC) in the presence of citric acid (CA) or 1,3-dimethylol-4,5-dihydroxy ethyleneurea (DM) as crosslinker agents. GLC can penetrate easily the wood cell walls, and after crosslinking, the cell wall is bulked. At 20% GLC concentration level, the leaching ratio of GLC incorporated into wood decreased from 73% to 15% in the presence of 10% CA or DM. The crosslinking efficiency of DM was higher than that of CA. The fixed chemicals in the cell walls caused ca. 6% permanent bulking, namely, a 43% reduction in volumetric swelling after water saturation. FTIR spectroscopy shows that GLC can be activated in the presence of a catalyst; however, the reaction of GLC with a wood polymer is very limited. Scanning electronic microscopy (SEM) reveals that some of the chemicals remained located in the cell lumens. The findings demonstrate that GLC alone is not efficient, but joint treatment of GLC with crosslinkers is a feasible way of wood modification.