Enhancing Weathering Resistance of Wood-A Review

Abstract

Wood is a truly sustainable and aesthetically pleasant material used in indoor and outdoor applications. Every material, including wood, is expected to have long-term durability and to retain its original appearance over time. One of the major disadvantages of wood is the deterioration of its surface when exposed outdoors, known as weathering. Although weathering is primarily a surface phenomenon, it is an important issue for wood products as it affects their appearance, service life, and wood-coating performance. To encourage the use of wood as a material for joinery and other building components, the results of research into increasing the weathering resistance of wood are extremely significant. The development of weathering protection methods is of great importance to reduce the maintenance requirements for wood exposed outdoors and can have a major environmental impact. There are various methods of protecting wood surfaces against weathering. This paper provides a literature survey on the recent research results in protecting wood from weathering. The topics covered include surface treatments of wood with photostabilizers; protection with coatings; the deposition of thin film onto wood surfaces; treatments of wood with inorganic metal compounds and bio-based water repellents; the chemical modification of wood; the modification of wood and wood surfaces with thermosetting resins, furfuryl alcohol, and DMDHEU; and the thermal modification of wood.

Keywords: chemical modification; coatings; nanoparticles; photostabilizers; plasma deposition; thermal modification; weathering; wood surface.

Figure 1

Colour change of uncoated (control) and coated beech wood with net coating and net coating with 1% nano TiO₂ after 12 months of natural weathering.

Figure 2

Schematic illustration of the formation process for the ZnO nanorod arrays on the wood surface ((a): row wood surface, (b): densely deposed ZN crystal seed onto wood surface, (c): large-scale ZnO nanorod arrays) [96]. Reprinted with permission from Springer Nature: Springer Nature, Journal of Materials Science (Improved UV resistance in wood through thehydrothermal growth of highly ordered ZnOnanorod arrays, Sun, Q. et al.), 2012.

Figure 3

Samples untreated and treated with coper-based preservatives and coated with alkyd-acrylic water-base coating after three years of natural weathering (CCA-chromated copper arsenate, ACQ-alkaline copper quat, CA-copper azole) [136]. Reprinted with permission from Springer Nature: Springer Nature, Journal of Coatings Technology and Research (Exterior wood coatings. Part-1: Performance of semitransparent stains on preservative-treated wood, Nejad, M. and Cooper, P.), 2011.

Figure 4

Reaction of wood with acetic anhydride [156]. Reprinted by permission from Springer Nature: Springer Nature, Journal of Journal of Coatings Technology and Re-search (Performance of finishes on wood that ischemically modified by acetylation, Beckers, E.P.J. et al.), 1998.