Hybrid Approach for Wood Modification: Characterization and Evaluation of Weathering Resistance of Coatings on Acetylated Wood

Abstract

Wood, as a biological material, is sensitive to environmental conditions and microorganisms; therefore, wood products require protective measures to extend their service life in outdoor applications. Several modification processes are available for the improvement of wood properties, including commercially available solutions. Among the chemical treatments, acetylation by acetic anhydride is one of the most effective methods to induce chemical changes in the constitutive polymers at the cellular wall level. Acetylation reduces wood shrinkage-swelling, increases its durability against biotic agents, improves UV resistance and reduces surface erosion. However, even if the expected service life for external cladding of acetylated wood is estimated to be 60 years, the aesthetics change rapidly during the first years of exposure. Hybrid, or fusion, modification includes processes where the positive effect of a single treatment can be multiplied by merging with additional follow-up modifications. This report presents results of the performance tests of wood samples that, besides the modification by means of acetylation, were additionally protected with seven commercially available coatings. Natural weathering was conducted in Northern Italy for 15 months. Samples were characterized with numerous instruments by measuring samples collected from the stand every three months. Superior performance was observed on samples that merged both treatments. It is due to the combined effect of the wood acetylation and surface coating. Limited shrinkage/swelling of the bulk substrate due to chemical treatment substantially reduced stresses of the coating film. Hybrid process, compared to sole acetylation of wood, assured superior visual performance of the wood surface by preserving its original appearance.

The Effects of Adding Heartwood Extractives from Acacia confusa on the Lightfastness Improvement of Refined Oriental Lacquer

“…Compared with the other wood coatings such as solvent-borne coatings including nitrocellulose lacquer, oil-modified alkyd resin, polyurethane resin, drying oil, etc., or other water-borne wood coatings, the ROL film has wide applications on wooden furniture and handicrafts in Taiwan, due to the wax-like gloss, elegant beauty, and excellent durability. It also exhibits biodegradability, identified as an important advantage of biomaterials from a sustainability perspective [ 9 ]. However, the inferior lightfastness of ROL, which is resulting in the primary component of catechol derivatives, needs to be improved for advanced uses.…”

Artificial Weathering of Contact-Charred Wood—The Effect of Modification Duration, Wood Species and Material Density

“…Uncoated structures develop a ‘driftwood’ appearance with uneven degradation, discoloration from the sun, and surface mold, and sometimes even rot in areas of constant water stress. This sort of wear leads to ‘aesthetic instability’ that necessitates replacement even if protective functions still remain [ 1 ]. Grüll et al [ 2 , 3 ] postulated that once cracking occurs, a limit state of the coated element is reached, and maintenance is required.…”

Special Issue “Wood Modification: Characterization, Modelling, and Applications”

“…The wide range of covered modification processes and the scope of applications proved that wood modification is not only the sole concern of a few wood scientists but it became a truly inter-disciplinary research area. Novel formulations, characterization methods, and serviceability are presented and deeply discussed in several publications contributing to the Special Issue [2][3][4][5][6][7]. A broad portfolio of characterization methods can be successfully implemented for the evaluation of complex mechanisms of deterioration process occurring during service life.…”

“…A broad portfolio of characterization methods can be successfully implemented for the evaluation of complex mechanisms of deterioration process occurring during service life. Artificial [2,3], natural [4,5], and combined [6] weathering methods are used for the assessment of the performance of different substrates and coatings. The performance of wood finished with a broad range of coatings systems is highly improved when compared to that of unmodified wood.…”

“…This confirms the great advantage of wood surface protection, especially when used in outdoor applications. Investigated coatings included transparent, semi-transparent, and opaque solutions based on different chemical compositions [3,4,6]. The performance of an innovative, bioinspired, and fully biobased coating system containing living fungal cells provides testimony for technological development.…”