Chemical modification of wood by non-formaldehyde cross-linking reagents

Abstract

The features of the reaction between sitka spruce wood and non-formaldehyde reagents, i. e. glyoxal, glutaraldehyde, and dimethylol dihydroxy ethyleneurea (DMDHEU), were investigated from the aspects of moisture adsorption and bending creep properties. To the moisture adsorption data, Hailwood-Horrobin adsorption equation was applied, and whole adsorbed water was separated into hydrated water and dissolved water which correspond to monolayer and multilayer adsorption, respectively. In the treatments with non-formaldehyde reagents, the decrease of equilibrium moisture content was mainly attributed to the decrease of dissolved water, but not largely to that of hydrated water. This suggested that the reagent in the multilayer adsorption region contributed pronouncedly to suppress the moisture adsorption by the bulking and cross-linking effects, but that the reagent in the monolayer adsorption region did not considerably. The creep deformation and remaining strain of the specimens treated with glyoxal and glutaraldehyde were as small as those of formaldehyde treatment. Also by the DMDHEU treatment, creep deformation was restrained to some extent. The eminent creep restraint effect by these treatments showed the formation of cross-linkings, although the crosslinkings were not stable to the drastic water leaching.

Chemical modification of wood by non-formaldehyde cross-linking reagents

“…Therefore, the bonds which restrain the recovery are probably unstable to the drastic water soaking condition, and this result was analogous to that of creep test reported previously (Yasuda et al 1994b). However, for the specimens cured for 1 to 3 h, the recovery after boiling increased more largely than that after soaking in cold water.…”

“…However, Weaver et al (1960) reported that these linkages were unstable, and we also observed that the excessive washing caused the decreases of ASE and restraining effect of creep deformation (Yasuda et al 1994b).…”

Enhancement of mechanical and thermal properties of Poplar through the treatment of glyoxal-urea/nano-SiO2

“…3c and Fig. 4a) 11,13,41,42 . The band at 1460 cm -1 caused by stretching vibration of the carbon-nitrogen (-C-N) bonds 40 increased significantly.…”

“…Due to its two active merged aldehyde groups, it can be used to glyoxylate the lignin in cell walls or crosslink with hydroxyl groups in cellulosic materials via a hemi-acetal or acetal reaction, in the presence of a catalyst [7][8][9] . In order to improve the dimensional stability of wood, previous researchers have used glyoxal as a cross-linking agent for wood modification [10][11][12][13][14] . All the modified wood in these studies exhibited excellent dimensional stability and reduced moisture absorption compared to the unmodified wood; however, the modification did not substantially improve the hardness of the wood.…”

Assessing the fire behavior of woods modified by N‐methylol crosslinking, thermal treatment, and acetylation

“…Besides wood‐inorganic composites, different approaches have been attempted for wood preservation, from chemical treatments, to coatings, to impregnations . Woods are also treated with dimethyloldihydroxy‐ethyleneurea (DMDHEU) to make them more resistant to weathering effects, termite infestation, and fungal infections, and to improve dimensional stability . DMDHEU acts as a crosslinking agent between cellulose microfibrils and is able to displace water in that interspace.…”