Superhydrophobic Wood Surface Research Articles

Construction of durable, multifunctional superhydrophobic wood surface via ɛ-polylysine/PDMS/wax treatment

In addressing the limitations of wood's susceptibility to water and moisture, this study explored the development of a durable, superhydrophobic surface through a novel ɛ-polylysine/polydimethylsiloxane (PDMS)/wax composite system. Leveraging the layer-by-layer (LBL) assembly, the incorporation of cationic ɛ-polylysine not only improved the adherence of PDMS and wax to the wood surface through electrostatic attraction but also facilitated a more uniform distribution, achieving optimal hydrophobicity at a ɛ-polylysine concentration of 2 g/L. The synergistic effect of the wood's natural rough structure and the deposition of these hydrophobic substances endowed the treated wood with superhydrophobic properties, showcasing exceptional self-cleaning capabilities by efficiently repelling a variety of liquid contaminants. Durability assessments through sandpaper abrasion, chemical exposure, and accelerated weathering tests confirmed the enhanced long-term stability of the treated wood surfaces. Furthermore, the incorporation of ε-polylysine provided nice antimicrobial properties, showing a substantial reduction in bacterial adhesion. The ε-polylysine/PDMS/wax composite system represents a significant advancement in the development of multifunctional wood surfaces, promising broader applications in sustainable building materials, furniture, and packaging solutions.

Fabrication of bulk superhydrophobic wood by grafting porous poly(divinylbenzene) to wood structure using isocyanatoethyl methacrylate.

Superhydrophobic treatment of wood can effectively reduce the interaction between wood and moisture, avoiding deformation, cracking, mould, and other defects caused by water absorption, which can extend the service life of wood and broaden the application field. Currently, the poor abrasion resistance of superhydrophobic wood is a crucial problem limiting its widespread application, and the preparation of superhydrophobic wood with robustness, abrasion resistance, and chemical resistance remains a huge challenge. In this work, robust bulk superhydrophobic wood with excellent abrasion resistance and chemical durability was fabricated by synthesizing porous poly(divinylbenzene) in wood cell cavities using graft copolymerization and solvothermal methods. The contact angles and rolling angles on the superhydrophobic wood surface were approximately 156° and 3°, respectively. Superhydrophobicity was carried through the entire structure of the wood. Even after severe damage by abrasion and sawing, as well as tests with organic solvents and harsh environments, the superhydrophobic properties of wood remained stable. Meanwhile, the superhydrophobic wood exhibited great self-cleaning and antifouling properties. In addition, the water uptake and dimensional stability of the wood were significantly improved. This work developed a simple, efficient, and durable strategy for the fabrication of superhydrophobic wood with robustness, abrasion resistance, and chemical resistance, which was expected to be applied to the wood industry to achieve the high-value applications of wood products and extend their service life.

Preparation of Superhydrophobic Wood Surfaces Modified Using MIL-88(Fe) via Solvothermal Method

A superhydrophobic wood surface was produced by employing the solvothermal method to form shuttle-like, well-crystallized MIL-88(Fe) on the surface of wood and assembling a Octadecylphosphonic acid (OPA) reagent. The nanosized MIL-88(Fe) molecule caused the wood’s surface to take on a nano mastoid shape. In addition, MIL-88(Fe) provides metal sites to capture OPA molecules, preventing the long-chain alkane hydrophobic group from contacting the surface of the wood. They both make a considerable difference in the growth of a hydrophobic wood surface. The results of the experiment indicate that the water contact angle (WCA) increases with reactant concentration. The WCA of the samples prepared with 5.0 × 10−2 M FeCl3 was 140.57°. When the reactant concentration was 10.0 × 10−2 M, the greatest WCA = 153.69° reading was obtained. The research’s findings present a novel technique for producing superhydrophobic wood surfaces.

Superhydrophobic Wood Surfaces: Recent Developments and Future Perspectives

Wood is a renewable material that has been widely utilized as indoor and outdoor construction and decoration material in our daily life. Although wood has many advantages (i.e., light weight, high strength, low price and easy machinability), it has some drawbacks that influence dimensional stability, cracking and decay resistance in real practical applications. To mitigate these issues, superhydrophobic surfaces have been introduced to wood substrates, creating superhydrophobic wood surfaces (SHWSs) that can improve stability, water resistance, ultraviolet radiation resistance and flame retardancy. Herein, the recent developments and future perspectives of SHWSs are reviewed. Firstly, the preparation methods of SHWSs are summarized and discussed in terms of immersion, spray-coating, hydrothermal synthesis, dip-coating, deposition, sol-gel process and other methods, respectively. Due to the characteristics of the above preparation methods and the special properties of wood substrates, multiple methods are suggested to be combined to prepare SHWSs rather than each individual method. Secondly, the versatile practical applications of SHWSs are introduced, including anti-fungi/anti-bacteria, oil/water separation, fire-resistance, anti-ultraviolet irradiation, electromagnetic interference shielding, photocatalytic performance, and anti-icing. When discussing these practical applications, the advantages of SHWSs and the reason why SHWSs can be used in such applications are also mentioned. Finally, we provide with perspectives and outlooks for the future developments and applications of SHWSs, expecting to extend the utilization of SHWSs in our daily life and industry.

Construction of a superhydrophobic wood surface coating by layer-by-layer assembly: Self-adhesive properties of polydopamine

To prevent moisture deformation, water swelling, severe mildewing, and decay due to the biodegradation of wood during outdoor use, a superhydrophobic wood surface coating was prepared by a layer-by-layer assembly method using polydopamine (PDA) and 1H,1H,2H,2H-perfluoro-decyl trichlorosilane (PFDTS). Due to its self-adhesive properties, PDA was used as an intermediate layer to connect the wood and PFDTS. PDA was first deposited on the wood surface to form a highly crosslinked granular structure that improved the surface roughness of wood. The wood surface was further modified by low-surface-energy PFDTS, and the wood after PDA deposition was superhydrophobic with a water contact angle (WCA) of 154°. The particle size of nano-PDA, as measured by laser particle size analysis, remained in the range of 0.57–2.73 μm. The surface morphologies of PFDTS/PDA coatings on glass plates were detected by EDF 3D microscopy, FE-SEM, and AFM. The bonding mechanism between coating components and wood surfaces was investigated by energy-dispersive spectroscopy, FT-IR spectroscopy, and X-ray photoelectron spectroscopy. The hydrophobic coating underwent rapid restoration and was resistant to both acidic and alkaline solutions (pH 2–12). This work provides a simple way to endow superhydrophobic properties to wood and has potential multifunctional applications for wood protection and new products.

Efficient recovery of superhydrophobic wax surfaces on solid wood

Superhydrophobic surface coatings have enormous potential to protect wood from excessive water uptake. Unfortunately, such coatings often require toxic chemicals or complex fabrication methods, and their mechanical stability is very limited. As an alternative, highly water-repellent wood surfaces with mean water contact angles (WCAs) of 160° were prepared by straightforward spray-deposition of alkyl ketene dimer (AKD) wax microparticles. While water repellency was unaffected by static loading with a cast iron weight, prolonged rubbing resulted in a strong reduction in WCA to 125° since the spherical wax microstructure was largely destroyed by the acting shear forces. Thermal treatment of such a degraded surface at 80 °C led to an almost full recovery (WCA 155°) of water repellency. Microscopy and thermal analysis revealed that exposure to temperatures above the melting range and subsequent slow cooling enable self-assembly of AKD into leaf-shaped microstructures, which are responsible for the high WCA observed. It is proposed that the thermally induced self-recovery ability will greatly enhance the utility and service life of AKD-based superhydrophobic wood surfaces and make them suitable for multiple practical applications.

Stable superhydrophobic wood surface constracting by KH580 and nano-Al2O3 on polydopamine coating with two process methods

Superhydrophobic treatment of wood is of great significance for improving the service life of wood and expanding its application fields. In this study, two process methods were designed to meet above requirements. Using polydopamine (PDA), 3-mercaptopropyltriethoxysilane (KH580) and nano-Al2O3 as the micro-nano structure maker and octadecyltrichlorosilane (OTS) as a low surface free energy agent to modify rough surface in order to prepare superhydrophobic wood samples (Wood@One-step and Wood@Two-step). The contact angle (CA) and sliding angle (SA) of the Wood@One-step were 155.3° and 4.76°, respectively; the CA and SA of the Wood@Two-step were 152.9° and 7.65°, respectively. Surface electron microscopy (SEM) images showed that the surface of Wood@One-step and Wood@Two-step were honeycomb structure and layered stacking structure respectively. The superhydrophobic properties of Wood@One-step were superior because of its more reasonable micro-nano roughness. Atomic force microscope (AFM) images presented that the nano-Al2O3 particles could effectively provide nano-level roughness. X-ray photoelectron spectroscopy (XPS) analysis showed that KH580 had covalent interaction with PDA. Thermogravimetric (TG) analysis, the immersion of acid-base solution and organic solution revealed that obtained superhydrophobic wood samples had excellent stability in the face of environmental challenges.

Construction of a Superhydrophobic Wood Surface Coating by Layer-by-Layer Assembly: Self-Adhesive Properties of Polydopamine

Construction of a Superhydrophobic Wood Surface Coating by Layer-by-Layer Assembly: Self-Adhesive Properties of Polydopamine

Development of highly durable superhydrophobic and UV-resistant wood by E-beam radiation curing

Developing a practical strategy to fabricate an anti-abrasion and durable superhydrophobic wood surface with ultraviolet (UV) resistance has great practical significance for expanding the application of natural wood. In this study, a robust superhydrophobic layer with a hierarchical micro/nano-roughness structure was modified on the wood surface through in-situ mineralization and polymerization using a simple sol–gel method along with efficient electron beam (EB) curing technology. Hydrophobic agent (polydimethylsiloxane, PDMS), and crosslinking monomer (γ-methacryloxypropyl trimethoxysilane, MAPS) form new covalent bonds between TiO2 particle layer and wood substrate after EB radiation, which endows robust superhydrophobicity and remarkable UV resistance on the wood surface. The as-prepared wood exhibited a water contact angle of approximately 165.7° and obvious repellency to many aqua-phase liquids (cola, strongly acidic, alkaline droplets etc.). Furthermore, the hierarchical micro/nano-protrusion structures remained unchanged and micro/nano particles aggregated tightly on the as-prepared wood surface under harsh external environments (sandpaper abrasion and, ultrasonic treatment), confirming the desirable anti-abrasion and mechanically durable performance of the superhydrophobic surface. After the 18-day UV accelerated weathering test, the TiO2 particle layer conspicuously retained the discoloration and maintained its exceptional repellency toward water. The biomimetic superhydrophobic wood with excellent mechanical durability and UV resistance reveals its potential application in the furniture and architecture fields.

Preparation of superhydrophobic wood surfaces via in-situ synthesis of Cu2(OH)3Cl nano-flowers and impregnating PF&STA to improve chemical and mechanical durability

Superhydrophobic wood surfaces had been fabricated via in-situ synthesis of Cu2(OH)3Cl nano-flowers. The modified wood surface exhibited improved water repellency as evidenced by an increased water contact angle (163° vs 50 to 75° for the control) and a sliding angle less than 5°. The modified wood surfaces remained hydrophobic after 12 h of exposure to strong acid (pH 2) or alkaline (pH 12), and the as prepared superhydrophobic surface was resistant to mechanical damage via 1000 cycles of tape removal and repeated sandpaper abrasion. The modified wood surface repelled not only water, but also milk, coke, and soy sauce, and showed a self-cleaning function. The results illustrate the promise of generating superhydrophobicity for improving the moisture resistance of timber surfaces. This work developed a simple, low-cost, and durable strategy for creating superhydrophobic wood surfaces, which has potential to be applied in wood industry to expand the service life of wood products.

Superhydrophobic wood surface fabricated by Cu2O nano-particles and stearic acid: its acid/alkali and wear resistance

Abstract Reducing the hydrophilic nature of wood could enhance dimensional stability and improve life cycle performance. Masson pine and pecan wood were modified to create superhydrophobic, self-cleaning functions by spray-coating with Cu2O nano-particles (Cu2O NPs)/phenol formaldehyde (PF) resin mixed solution followed by immersion in a stearic acid ethanol solution. Two types of Cu2O NPs, derived from different concentrations of copper chloride (CuCl2) were evaluated for their ability to improve hydrophobicity of wood surface. A special petal-shaped structure on the edge of Cu2O NPs was found on modified pecan wood, and water contact angles (WCA) of both kind of modified wood reached around 155° and sliding angles (SA) less than 10°. Meanwhile, low liquid permeability and excellent repellency to aqueous solutions with pH = 1 to 13 were achieved. The critical WCA around 150° was also maintained on modified wood surfaces after being immersed in strong acid (pH = 2) and strong alkali (pH = 12) solutions for 12 h. Furthermore, remarkable mechanical durability was obtained after harsh abrading test, which could be attributed to the high bond strength from cured PF resin adhesive. Such highly waterproof, acid/alkali resistant and hard-wearing superhydrophobic surface must have potential to be widely applied in wood products industry.

Surface physical structure and durability of superhydrophobic wood surface with epoxy resin

In this study, a superhydrophobic wood surface was prepared with amino-functionalized nano-silica (SiO2) particles, epoxy resin (EP) of different curing times, and octadecyltrichlorosilane (OTS). The micro-nano structures of the wood samples were represented by scanning electron microscopy (SEM), while the hydrophobicity and durability of the hydrophobic effect was shown by the contact angle (CA) tests. The results indicated that the optimal curing time of EP was 4 h, such that the wood surface exhibited promising superhydrophobicity with a static CA of 155.4° and a sliding angle (SA) of 3.9°. The different curing time of EP had a remarkable influence on the roughness and the pore structure type of superhydrophobic wood surface. In terms of the Cassie-Baxter theory, the increase of CA on the wood surface was ascribed to the presence of secondary air pores and rough structure in the solid-liquid interface. The obtained wood surface not only possessed excellent adhesion stability and anti-aging properties, but also a resistance to acidic solutions, organic solvents, and mechanical abrasion.

A cost effective strategy to fabricate STA@PF@Cu2O hierarchical structure on wood surface: aimed at superhydrophobic modification

Cuprous oxide nanoparticles (Cu2O NPs), phenol formaldehyde (PF) resin, and stearic acid (STA) were used to fabricate hierarchical core/shell structures to endow wood with superhydrophobic function, in which the preparation of Cu2O NPs and the synthesis of PF were carried out simultaneously in one system. The Cu2O NPs with the shape of a symmetrical tetrahexahedron were prepared in this work, and this novel shape is beneficial for creating a superhydrophobic surface. A relatively rough structure in micro/nanoscale was formed on the wood surface after being sprayed with PF@Cu2O coating, which played a vital role in the fabrication of superhydrophobic wood surfaces, as expected. Morphological analysis and surface free energy calculations verified that STA reduced the surface free energy. Application of 12 layers of PF@Cu2O coating followed by 2 h immersion in STA ethanol solution produced wood surfaces with low water permeability and high water contact angles of 153.3°, 153.2°, 150.5° on cross, radial, and tangential sections, respectively. Abrasion tests coupled with subsequent exposure to acidic and alkaline conditions indicated that the coating was resistant to both mechanical wear and chemical degradation. This two-step coating strategy used inexpensive ingredients and could have potential to application as water repellency protection of wood timber.

Manufacturing of robust superhydrophobic Wood surfaces based on PEG–Functionalized SiO2/PVA/PAA/Fluoropolymer hybrid transparent coating

Inspired by the unique characteristics and special surface of morph–genetic materials in the living nature, discovering surfaces of super–wettability such as “lotus leaves, red rose petals, gecko feet, Salvinia leaf, and so on”, a number of researchers have been used various methods to create the biomimetic structures with nano/micro–manufacturing and a low energy surface. Recently, extensive attention has been paid to improving multi–functional robust superhydrophobicity and high optically transparent superhydrophobic surfaces. Herein, a simple and novel method was proposed to synthesize a large area of biomimetic robust superhydrophobic transparent coating, which is based on PEG–functionality SiO2/PVA/PAA/Fluoropolymer coating with nano/micro–manufacturing structures, and has excellent durability and robustness on wood surface using a multi–solvent continuous modification method. The as-prepared biomimetic wood has a robust mechanical nanostructures, which not only has a relatively high UV transmittance of 72% at 550 nm, but also has excellent durability under mechanical shock and different temperature condition. Moreover, it also possess superhydrophobicity and superior water–resistant with a water contact angle of 159°, which is mainly due to the fact that the surface of superhydrophobic coating consists of nanoparticles aggregated with each other in an arrangement of pillars structure enveloping the nanoparticles to form a complete micro–nano binary rough structure via biomimetic PEG–functionalized SiO2/PVA/PAA/Fluoropolymer hybrid transparent coating, outperforming the untreated wood timber. Meanwhile, an amplified load effect existed within the creep under cyclic moisture changes, which the sportive mechanical creep properties of as–prepared biomimetic robust superhydrophobic wood only displayed conventional creep characteristics, implying that a superior mechanical performance would act on moisture content on the superhydrophobic coating. These design strategies can lead to the development of other self–cleaning superhydrophobic and switchable adhesive superhydrophobic materials for harsh operating environments.

Robust superhydrophobic wood surfaces with mechanical durability

Mechanical durability of superhydrophobic wood surfaces has significant practical meaning for civil engineering and architecture. The existing methods for fabricating superhydrophobic wood surfaces used complex processes and large amounts of chemical reagents, which bought a heavy burden to the environment. Herein, superhydrophobic wood surfaces with robust mechanical durability were fabricated by a simple, efficient and green method. Only a non-toxic chemical solution of silver nitrate (AgNO3) was used during the whole fabrication process, which was green and environmentally friendly. The wettability of the as-fabricated surface was studied. The effects of external loading, including cyclic tape peeling, sandpaper abrading, and knife scratching on the changes of superhydrophobicity and relevant mechanism were investigated. It is found that due to Cu layer worked as a binder of micro-nano dendritic structures, the hierarchical micro-nano dendritic structures kept unchanged and nanoparticles always existed on the as-fabricated surface under tape peeling, sandpaper abrading and severe knife scratching, making the surface display robust mechanical durability. It is expected that the superhydrophobic wood with mechanical durability has good application prospects in civil engineering and architecture field.

Fabrication of Superhydrophobic Wood Surface by Etching Polydopamine Coating with Sodium Hydroxide

Superhydrophobic treatment of wood surfaces can effectively prevent the contact between the external moisture and wood, which improves the service life of the wood. In this study, different rough surfaces of wood were constructed, derived from the self-polymerization of dopamine (DA) in weak base solution to form a polydopamine (PDA) coating and the deprotonation of the PDA coating in a strong base solution. Furthermore, octadecyltrichlorosilane (OTS) was used as a low-surface-free-energy agent to modify rough surface in order to prepare superhydrophobic woods: Wood@PDA–NaOH–OTS and the Wood@PDA–NaOH/SiO2–OTS. The contact angles (CAs) and sliding angles (SAs) of the resulting superhydrophobic woods were tested. The results showed that the CA and SA of the Wood@PDA–NaOH–OTS were 151° and 4.8°, respectively; the CA and SA of the Wood@PDA–NaOH/SiO2–OTS were 155.1° and 5.0°, respectively. Surface electron microscopy (SEM) images presented that NaOH successfully etched the PDA coating, and the roughness was further improved by adding nano-SiO2. Atomic force microscope images (AFM) revealed that the nano-SiO2 particles could effectively provide nanolevel roughness, which was beneficial to the wood’s superhydrophobic properties. In addition, the obtained superhydrophobic wood possessed strong surface stability and anti-loss property, as well as resistance to acid-base solution and organic solvent.

Facile preparation of superhydrophobic wood surfaces via spraying of aqueous alkyl ketene dimer dispersions.

The prevention of excessive water uptake in wood in order to avert discoloration, swelling and decay is a major challenge for wood-based applications. We developed a facile surface treatment to protect wood from liquid water uptake that does not require harsh process conditions or toxic solvents. Water-based and surfactant-free dispersions of sub-micron alkyl ketene dimer wax particles were prepared and sprayed onto wood substrates. After the evaporation of water, the wax particles self-assembled into distinctive platelet structures. Depending on the specific conditions of application, water contact angles as high as 166° were measured on treated wood surfaces. The implementation of sub-micro structures clearly reduced surface gloss but transparency and color remained largely unaffected. The method is comparably cost-effective and scalable, overcoming dimensional limitations crucial for many applications of wood.

A simple fabrication of superhydrophobic wood surface by natural rosin based compound via impregnation at room temperature

A two-step impregnation method containing first modification with natural rosin based compound (maleic rosin) and subsequent coating with TiO2 particles was used for the fabrication of a stable superhydrophobic wood surface. The superhydrophobic property of the treated wood was measured by static contact angel (CA) and dynamic CA. The morphology and chemical composition of the superhydrophobic wood surface were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The chemical bonds between maleic rosin/TiO2 and wood were illustrated by Fourier transform infrared spectroscopy. The water CA of the modified wood surface could reach up to 157°. The prepared superhydrophobic wood surface still maintained the superhydrophobic property when being immersed in water for 1 week or irradiated under scorching sunlight for 1 week or boiled at 100 °C for 10 h. Possible formation mechanism of superhydrophobic composite surface on the wood substrate was discussed in detail.

Facile preparation of mechanically durable, self-healing and multifunctional superhydrophobic surfaces on solid wood

Maintaining the hierarchically roughened structures and non-wetting properties are critically essential for a superhydrophobic surface upon sunlight irradiation, physical rubbing or organic contamination in practical applications but remain extremely challenging. Herein, by simply spraying a waterborne perfluoroalkyl methacrylic copolymer (PMC) emulsion mixed with TiO2 nanoparticles onto polydimethylsiloxane (PDMS) pre-coated substrates, mechanically durable, self-healing superhydrophobic surfaces were fabricated on solid wood. The coated surfaces exhibited exceptional repellency toward water as well as organic liquids with low surface tensions including ethylene glycol. The as-prepared coatings on the rigid wood substrate showed excellent durability against mechanical abrasion while retaining the rough surface textures due to the hydrophobic binder PMC anchoring the nanoparticles tightly on the surface, thus sustaining the superhydrophobicity of the surface. Moreover, the non-wetting properties of the surface damaged by ultraviolet (UV) irradiation can be automatically restored by a simple heat treatment, which facilitates the migration of the underlying hydrophobic PDMS onto the surface replenishing the necessary low-surface-energy materials. Besides, the TiO2-containing coatings exhibited photocatalytic activity in degrading organic contaminants and can also preserve the underlying wood substrate from photodegradation during UV exposure. The developed method herein features environment-friendly raw materials, facile processing and large-scale fabrication. Such superhydrophobic wood surfaces with multi-functionalities may open new avenues in the field of novel wood-based materials.

Preparation of Stable Superhydrophobic Coatings on Wood Substrate Surfaces via Mussel-Inspired Polydopamine and Electroless Deposition Methods.

Mussel-inspired polydopamine (PDA) chemistry and electroless deposition approaches were used to prepare stable superhydrophobic coatings on wood surfaces. The as-formed PDA coating on a wood surface exhibited a hierarchical micro/nano roughness structure, and functioned as an “adhesive layer” between the substrate and a metallic film by the metal chelating ability of the catechol moieties on PDA, allowing for the formation of a well-developed micro/nanostructure hierarchical roughness. Additionally, the coating acted as a stable bridge between the substrate and hydrophobic groups. The morphology and chemical components of the prepared superhydrophobic wood surfaces were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The PDA and octadecylamine (OA) modified surface showed excellent superhydrophobicity with a water contact angle (CA) of about 153° and a rolling angle (RA) of about 9°. The CA further increased to about 157° and RA reduced to about 5° with the Cu metallization. The superhydrophobic material exhibited outstanding stability in harsh conditions including ultraviolet aging, ultrasonic washing, strong acid-base and organic solvent immersion, and high-temperature water boiling. The results suggested that the PDA/OA layers were good enough to confer robust, degradation-resistant superhydrophobicity on wood substrates. The Cu metallization was likely unnecessary to provide significant improvements in superhydrophobic property. However, due to the amazing adhesive capacity of PDA, the electroless deposition technique may allow for a wide range of potential applications in biomimetic materials.