Abstract
Titanium dioxide (TiO
2
)/graphene oxide (GO)-treated wood was fabricated through a one-step hydrothermal-vacuum dipping technique, in which silica sol serves as a dispersant and linker ...owing to its good stability and high surface area, while the visible light activates TiO
2
/GO and negative oxygen ions (NOI) arise. This approach exhibits a super dye adsorption capacity and enhanced photocatalytic efficiency. In focus was the effect of the three-dimensional (3D) GO dopant on the NOI production, which was very high in this system. Namely, the concentration of NOI is up to 1710 ions cm
−3
after 60 min visible light irradiation. Moreover, recycling experiments show that the properties of a TiO
2
/GO-wood system are stable. The TiO
2
/GO-treated wood is a healthy, environmentally friendly material which is promising for indoor decoration.
Improving the environmental performance of resins in wood treatment by using renewable chemicals has been a topic of interest for a long time. At the same time, lignin, the second most abundant ...biomass on earth, is produced in large scale as a side product and mainly used energetically. The use of lignin in wood adhesives or for wood modification has received a lot of scientific attention. Despite this, there are only few lignin-derived wood products commercially available. This review provides a summary of the research on lignin application in wood adhesives, as well as for wood modification. The research on the use of uncleaved lignin and of cleavage products of lignin is reviewed. Finally, the current state of the art of commercialization of lignin-derived wood products is presented.
Wood modification, an efficient approach to enhance the intrinsic properties of wood, has been extensively studied for decades. Due to growing environmental awareness, the sustainability of wood ...modification has received more attention. Generally, the sustainability in wood modification should consist of three aspects: an environmentally friendly processes, renewable modifying agents, and nontoxic and biodegradable resultant products. Recently, some biobased modifying agents obtained from renewable feedstocks were explored for substituting the petroleum-based ones. This review focuses on representative wood modification methods, including furfurylation, impregnation with natural products and biodegradable polymers, and chemical modification with sustainable reagents, since these methods have the potential to enhance wood properties. However, there are many challenges for using these agents, including effectiveness in penetration, evenness in distribution, and durability. The cost, process conditions, and equipment of these methods could also be challenges for scaling up. In addition, current studies mainly pay attention to the green reagent selection and property enhancement, rather than environment behavior evaluation of the resultant products. Effort should be made to evaluate the ecotoxicity and degradation behavior of the modified wood since it can help us determine whether the new formulations are sustainable. Much work needs to be done to overcome the obstacles above-mentioned and to develop efficient modification methods with a minimum environmental impact.
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•Chemical heterogeneity is a common challenge in the application of biomaterials such as wood.•Chemical imaging methods unravel spatial heterogeneity in wood on different length ...scales.•These methods can quantify the chemical distribution in treated wood on macroscopic and cellular levels.•Combining imaging methods provides a holistic insight into structure–property relations of biomaterials.
An inhomogeneous chemical distribution can be problematic in many biomaterial applications, including wood impregnation. Since wood is a hierarchically structured material, the chemical distribution must be considered on different length scales. Here, a combination of imaging methods revealed the distribution of phenol–formaldehyde resin in impregnation-treated European beech wood within the scale of several millimeters or larger (macroscopic) and the micron scale (cellular level). The macroscopic resin distribution was quantified by hyperspectral near-infrared (NIR) image regression. A partial least square regression model accurately predicted the resin content in the range of 0–30 % with average prediction errors of ≤0.93 % for calibration and the test set. The cellular resin distribution was investigated by mapping the UV absorbance in selected regions of interest at high lateral resolution using UV microspectrophotometry (UMSP). The application of both imaging techniques to board sections revealed a process-dependent resin distribution. NIR image regression quantified the drying-induced migration of resin toward the board surfaces. UMSP measurements in selected regions revealed that this resin migration also affected the resin distribution across cell walls. Overall, the results demonstrate the potential of combining chemical imaging techniques to quantify process-dependent heterogeneity and to develop efficient treatments for wood and other biomaterials.
Citric acid (CA) can be found naturally in fruits and vegetables, particularly citrus fruit. CA is widely used in many fields but its usage as a green modifying agent and binder for wood is barely ...addressed. Esterification is one of the most common chemical reactions applied in wood modification. CA contains three carboxyl groups, making it possible to attain at least two esterification reactions that are required for crosslinking when reacting with the hydroxyl groups of the cell wall polymers. In addition, the reaction could form ester linkages to bring adhesivity and good bonding characteristics, and therefore CA could be used as wood binder too. This paper presents a review concerning the usage of CA as a wood modifying agent and binder. For wood modification, the reaction mechanism between wood and CA and the pros and cons of using CA are discussed. CA and its combination with various reactants and their respective optimum parameters are also compiled in this paper. As for the major wood bonding component, the bonding mechanism and types of wood composites bonded with CA are presented. The best working conditions for the CA in the fabrication of wood-based panels are discussed. In addition, the environmental impacts and future outlook of CA-treated wood and bonded composite are also considered.
•A novel modified engineered wood product, namely, plywood made from acetylated birch veneers.•Exhaustive dataset of mechanical properties of acetylated birch plywood in tension, compression, panel ...shear, and edgewise bending.•Significant angle dependence of the presented strength and elastic properties.•Comparison with ordinary unmodified birch plywood regarding strength, stiffness and failure modes.
There is an increasing demand for engineered wood products (EWPs) due to the flourish of modern timber structures during recent years. However, the durability-related issues are still unignorable limitations when applying timber to outdoor structures. Therefore, treatment measures are still needed to enhance the durability of timber. The acetylation process, which involves the reaction between acetic anhydride and wood, has been widely studied as a wood modification method during the past decades. Several experimental studies have proven acetylation to effectively reduce wood's hygroscopicity while improving its dimensional stability and fungal decay resistance. For load-bearing timber structures, especially those in the outdoor environment, the combination of acetylation and EWPs gives the possibility to manufacture more durable and stable timber elements in the context of dimensions and mechanical properties. This study concerns the mechanical and elastic properties of acetylated birch plywood. More specifically, tensile, compressive, shear and bending tests were conducted under three different load-to-face grain angles, namely from 0° (parallel), 22.5°, to 45°. The test results were thereafter compared with ordinary unmodified birch plywood concerning stress–strain relationships, failure modes, strength, and elastic properties.
•Mass, strength and stiffness losses attributed to the thermal treatment were entirely recovered by the in situ polymerization of styrene;•The combined treatment also yielded increases in surface and ...volumetric hydrophobicity;•That wood treated by the two-step treatment showed high aesthetical attributes related to its dark surface colour;•The thermal treatment acted as a pre-treatment facilitating the post impregnation and retention of the polymeric substance.
This study deals with a two-step treatment, in which a thermorretification at 180 °C for 2 h is followed by the in situ polymerization of polystyrene into a fast-growing pine wood. The treatment with polystyrene recovered losses in both stiffness and strength attributed to the thermal modification. Compared to the heat-treated wood, the two-step treated pine wood presented higher thermal stability (40%), termites resistance (8%), water uptake (300%), hydrophobicity, along with similar decay resistance, and surface colour and roughness.
Wooden building materials have advantages in terms of biodegradability, non-toxicity, pollution-free and recycling. Currently, applications of natural wood are extremely limited because of low ...density, low strength and toughness. Therefore, we reported an effective modification strategy with nano-scale cellulose nanofibrils design to prepare a synergistically enhanced cellulosic material. Via three steps: i) the secondary alcohol hydroxyl groups in C2, C3 position were cut; ii) oxidize the hydroxyl group at C2, C3 position to achieve dialdehyde cellulose; and iii) oxidized again to obtain dicarboxylic cellulose. Subsequently, thanks to the regulation of the average moisture content, the moisture content in the wood surface and subsurface increased in a short time. The wood softening layer contributes to the hotpressing treatment of the wood. The mechanical properties and dimensionality have been greatly improved. The obtained delignified oxidated hot-pressed wood with 0.55 mmol/g carboxyl group content demonstrates excellent strength of 328.8 ± 7.43 MPa and Young's modulus of 8.1 ± 0.14 GPa, which is twice than that of natural wood. Delignified oxidated hot-pressed wood also shows exceptional toughness of 8.3 ± 0.28 MJ/m3. Other than that, the shore hardness indicates 0.55 mmol/g carboxylic group, which could increase the hardness at the wood surface hardness to 72.5 ± 4.29°.
High-strength, dimensionally-stable, moisture-absorbing, and heat-insulating materials are critical for ensuring the safety of building structures and human comfort. As a natural moisture-adjusting ...and heat-insulating material, wood is widely used in buildings, but its low strength and flammability pose safety hazards. This paper reports a simple method to construct an organic-inorganic hyperbranched structure in poplar wood (WSi-Al-EP). The bending and compressive strength of WSi-Al-EP reached 103.50 MPa and 80.41 MPa, respectively. This composite wood material exhibited high strength and stable performance, and it also improved the shortcomings of traditional inorganic-modified materials such as unstable sizes and the loss of modifiers. Moreover, the material did not burn in a long-term high-temperature flame, indicating its heat and combustion resistance, and showing that it can be used in wooden building structures.
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•A method for preparing organic-inorganic hyperbranched structure in wood (WAl-Si-EP).•WAl-Si-EP has high strength and good dimensional stability.•WAl-Si-EP has strong thermal stability and flame resistance.
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•DMSO is carried by scCO2 into wood cell walls where it triggers swelling of fibres.•DMSO-induced swelling of wood largely improves dye uptake.•Scanning densitometry is a powerful ...analytical tool to quantify wood colouration.•It is superior to CIELAB analysis in terms of sample throughput and selectivity.
Supercritical dyeing of wood is a smart green technology. Beyond being of interest to wood industry, it could help to preserve tropical forests and decrease the environmental pollution from overseas shipping. However, scCO2 dyeing is still in its infancies. This paper demonstrates at the example of three major European hardwood species and the dye Naphthazarin that the uptake of colorants can be improved if scCO2 is complemented with small amounts of DMSO. The latter triggers micro-swelling of wood, thereby improving dye penetration. Systematic variation of process parameters revealed that optimal colouration is reached at 20.0 MPa and 85 °C. Colour gradients as observed in the interior of halved specimen were evaluated by two methods. While the Euclidean distance ΔE (CIELAB) represents relative colour change only, a recently proposed scanning densitometric approach translates colour depth into absolute dye surface concentration. Morphological investigations conceal this study investigating the impact of selected process conditions.
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