The common method to impregnate wood with polyethylene glycol (PEG) is to store the samples for several weeks in aqueous PEG-solution, allowing for diffusion of PEG into the wood. As this method is poorly suited for industrial application, an alternative approach based on vacuum-pressure treatment is evaluated in the present study. Using European oak wood and three variants of PEG, including silane-functionalized PEG, impregnation experiments at different PEG concentrations were performed. Significant uptake of PEG resulted in clearly altered wood-water relations and improved dimensional stability of oak wood. These results are discussed in terms of stability in humid and aqueous environments, and in terms of effects of the anatomy of oak wood on differences in dimensional stabilization observed along the radial and tangential anatomical directions, respectively. While both of the PEG variants perform better with an anti-shrinkage efficiency of up to 80%, the PEG-silane variant performs less effectively in this respect; however PEG-silane is clearly predominant in case of water extraction.

Surfactant-free aqueous wax dispersions for the novel preparation of self-assembled superhydrophobic alkyl ketene dimer coatings on intrinsically hydrophilic wood substrate.

Due to their bio-based character, oil-based coatings become more and more prevalent in wood surface finishing. These coatings impart appealing optical and haptic properties to the wood surface, but lack sufficient protection against water and mechanical influences. The present study reports a simple green route to improve the performance of linseed oil coating by the addition of nanofibrillated cellulose (NFC). In order to achieve surface chemical compatibility with linseed oil, NFC was chemically modified with acetic anhydride and (2-dodecen-1-yl)succinic anhydride, respectively, using propylene carbonate as a solvent. NFC/linseed oil formulations were prepared and applied to wood substrates. The wear resistance of oil-coated wood surfaces was assessed by a newly developed test combining abrasive loading with subsequent contact angle measurement. As revealed by infrared and nuclear magnetic resonance (NMR) spectroscopy, as well as X-ray diffraction (XRD), NFC has been successfully modified without significantly affecting the structure of cellulose. In abrasion tests, all NFC-modified oil coatings performed better than the original oil. Interestingly, NFC only suspended in propylene carbonate, i.e., without chemical modification, had the strongest improvement effect on the coating’s wear resistance. This was primarily attributed to the loose network structure of this NFC variant which effectively prevents the oil from penetration into the wood surface, thus forming a protective NFC/oil composite layer on the wood surface.

The applicability of amino acid tricine has been investigated for the modification of solid wood. Oak, walnut, cherry, and birch wood lamella were impregnated with a tricine solution and subjected to a drying process. The interaction between tricine and wood components was analyzed by attenuated total reflectance-Fourier transform infrared and nuclear magnetic resonance spectroscopy, and the reactions only with hemicelluloses were detected. Xylosylamine structures were found among the reaction products of xylose and tricine, and solid oak wood also showed this type of reaction. The equilibrium moisture content of the modified wood decreased, and this finding was interpreted as an indication of a modification of the polysaccharides. The hardness and tensile strength of the tricine-modified lamellae increased significantly. The change of the physical properties is probably due to the low moisture content with increased hydrogen bonding between wood cell wall components. A crystalline layer of tricine on the cell walls was observed by means of electron microscopy.