Fabrication of Durable Hydrophobic/Superhydrophobic Wood Using an Alkyl Ketene Dimer by a Simple and Feasible Method

Abstract

To improve the hydrophobicity of precious hardwood, a facile sanding pretreatment and alkyl ketene dimer (AKD) modification were performed. After the AKD modification, the wood was highly hydrophobic, and the contact angle was 143°. The increased hydrophobicity could be attributed to the ester bond formed between the wood hydroxyl groups and AKD, which was confirmed by attenuated total reflectance–Fourier transform infrared spectroscopy. Sanding pretreatment could further greatly increase the wood hydrophobicity and render it superhydrophobic, not only in a cross-section but also in the tangential and radial sections. The changed wood surface roughness could be responsible for the increased hydrophobicity, which was confirmed by characterization with a scanning electron microscope (SEM) and a three-dimensional optical microscope. Apart from the improved hydrophobicity, the AKD-modified wood exhibited excellent water, acid, and toluene resistance. After a 12 h immersion, the contact angle did not change significantly, and the acid immersion contributed to an improvement in the hydrophobicity of the wood. Furthermore, the resultant AKD-modified wood exhibited an excellent self-cleaning effect.

Superhydrophobic Wood Surfaces: Recent Developments and Future Perspectives

“…For example, Yang et al prepared durable SHWSs by using a two-step impregnation consisting of chemical modification with natural maleic rosin and subsequent coating with TiO 2 nanoparticles to increase surface roughness [124]. Of course, the impregnation approach can be improved by the assistance of vacuum with pressure (i.e., 0.01 MPa [125], 0.5 MPa [125] and −0.1 MPa [13]). Liu et al realized SHWSs by the impregnation of a silica/silicone oil complex emulsion into wood substrates with the help of vacuum (i.e., 0.01 MPa for 1 h and 0.5 MPa for 1 h) and drying with different temperatures (i.e., 60 • C for 12 h, elevated to 80 • C for 12 h, and elevated to 103 • C for drying) [125].…”

“…It possesses a lot of advantages, such as light weight [3], high strength [4], easy machinability [5], renewability [6], thermal insulation [7], aesthetic characteristics [8], low price [9] and environmental friendliness [10]. For thousands of years, wood has been extensively utilized in various applications, including fuels [11], indoor and outdoor construction and decorations [12][13][14][15], tools [16], papers [4] and furniture [17]. Due to rich hydroxyl groups, the hydrophilic wood is susceptible to water [3], fire [5], pollutants [18], insects [7], living microorganisms (i.e., bacteria and fungi) [19][20][21] and weathering factors (i.e., acidic rain and UV lights) (Figure 1) [14,15,22], resulting in its dimensional instability (i.e., swelling and shrinking), cracking, decay and degradation [3,9,11,23].…”

Recent Advances in Superhydrophobic Surfaces and Applications on Wood

“…To improve the hydrophobicity of hardwoods, according to the research of Cao et al [ 32 ], the sapwood of birch, oak, and black walnut, was modified with grafted alkylenone dimer (AKD), as shown in Figure 4 . After AKD modification, the hydroxyl group reacts with AKD to form a hydrophobic layer.…”

Research Progress on the Improvement of Flame Retardancy, Hydrophobicity, and Antibacterial Properties of Wood Surfaces

“…Wood is a popular material for furniture and floor manufacturing as well as other industries since it is inexpensive, simple to produce, beautifully patterned, naturally renewable, and low-carbon [ 44 , 72 , 73 , 74 , 75 ]. However, wood cell walls are composed of cellulose, etc., and the hydroxyl groups on its branch chains combine with water to create hydrogen bonds, resulting in the wood itself being significantly hydrophilic [ 76 , 77 ].…”

“…It is prone to corrosion in a humid environment, resulting in cracking, mildew, greatly reducing the durability of wood, resulting in resource waste, and economic losses [ 78 , 79 , 80 ]. The improvement of wood’s surface hydrophobic property can effectively improve its water-resistance, form an anti-fouling and anti-mildew surface, reduce unnecessary damage, and prolong its service [ 72 , 81 ].…”