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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.
Wood is undeniably the most useful and readily available natural raw material. However, the susceptibility of wood products to fire is one of the crucial challenges faced in the wood industry. The ...fire behaviour of wood is a very complex phenomenon due to the different constituents and their independent reactions to fire. This article presents a thorough overview of the flammability stages of wood. It covers pyrolysis, thermal oxidative decomposition, ignition, combustion and heat release as well as flame extinction mechanisms. In the area of flame retardancy, conventional wood fire retardants, nanocomposites fire retardants and wood modification processes are investigated. Factors such as wood species, moisture content, density, experimental conditions such as external heat flux, heat exposure time, wood permeability and porosity are some of the deterministic parameters characterising the fire behaviour. This paper is a one-stop-shop for researchers analysing wood flammability due to the inclusion of all aspects pertaining to the burning of wood.
With the increasing demands on sustainability in the material science and engineering landscape, the use of wood, a renewable and biodegradable material, for new material development has drawn ...increasing attentions in the materials science community. To promote the development of new wood-based materials, it is critical to understanding not only wood's hierarchical structure from molecule to macroscale level, but also the interactions of wood with other materials and chemicals upon modification and functionalization. In this review, we discuss the recent advances in the Raman imaging technique, a new approach that combines spectroscopy and microscopy, in wood characterization and structural evolution monitoring during functionalization. We introduce the principles of Raman spectroscopy and common Raman instrumentations. We survey the use of traditional Raman spectroscopy for lignocellulosic material characterizations including cellulose crystallinity determination, holocellulose discrimination, and lignin substructure evaluation. We briefly review the recent studies on wood property enhancement and functional wood-based material development through wood modification including thermal treatment, acetylation, furfurylation, methacrylation, delignification. Subsequently, we highlight the use of the Raman imaging for visualization, spatial and temporal distribution of wood cell wall structure, as well as the microstructure evolution upon functionalization. Finally, we discuss the future prospects of the field.
Chemical modification as a non-biocidal treatment is an effective method to improve physical and biological properties of wood. Poplar is a fast growing species but has poor dimensional stability and ...durability in addition to low mechanical properties. Low molecular weight Dimethylol dihydroxyethyleneurea (mDMDHEU) was used to improve the properties of poplar mainly dimensional stability and decay resistance. Results indicated high anti-swelling efficiency (ASE), but low variation between both concentrations of mDMDHEU. Tangential swelling was greatly reduced by mDMDHEU treatment during the water immersion period. Untreated poplar samples were severely decayed as compared to modified samples. Modified samples showed lower bending strength unlike to compression strength. Ester peak at 1720 cm-1 revealed chemical reaction between chemical reagent and wood cell wall components. Control samples exhibited considerably higher thermal degradation when compared to the samples modified with mDMDHEU.
Kemijska modifikacija kao postupak bez biocida učinkovita je metoda za poboljšanje fizičkih i bioloških svojstava drva. Topolovina je drvo vrste koja brzo raste, ali ima slabu dimenzijsku stabilnost i prirodnu trajnost te slaba mehanička svojstva. Za poboljšanje svojstava topolovine, prije svega dimenzijske stabilnosti i otpornosti na propadanje, upotrijebljena je dimetilol dihidroksietilenurea male molekularne mase (mDMDHEU). Rezultati su pokazali visoku učinkovitost kemijske modifikacije u smislu sprječavanja bubrenja topolovine (ASE), ali s malom varijacijom među dvjema primijenjenim koncentracijama mDMDHEU-a. Tangencijalno bubrenje uzoraka topolovine tijekom uranjanja u vodu uvelike je smanjeno mDMDHEU modifikacijom. Nemodificirani uzorci topolovine bili su vrlo truli u usporedbi s modificiranima. Modificirani su uzorci, pak, pokazali manju čvrstoću na savijanje u usporedbi s tlačnom čvrstoćom. Vrh vrpce na 1720 cm-1 otkrio je kemijsku reakciju između kemijskog reagensa i spojeva u staničnoj stijenci drva. Na kontrolnim je uzorcima nastala znatno veća toplinska degradacija nego na uzorcima modificiranima mDMDHEU-om.
Mass timber (MT), a group of large engineered structural wooden panels such as cross-laminated timber (CLT), glue-laminated timber (Glulam), laminated veneer lumber (LVL), etc., is becoming ...increasingly popular due to sustainable construction. Despite the numerous benefits of MT-based buildings, such as low-carbon emission, short construction time, and cost-effectiveness, the concerns regarding the durability of MT may limit their market acceptance. In this review, we discuss the advantages and opportunities of applying MT in tall buildings, as well as the durability issues associated with MT application. We examine the traditional wood protection techniques including, preservative treatment, thermal and chemical modification, and discuss the potential of applying these techniques for MT protection. We survey the recent studies on MT durability evaluation, as well as the recent progress in MT structure protection through a moisture control strategy. Finally, we highlight the MT protection strategies through the preservative, thermal, and chemical treatment approaches, review the effects of these treatment methods on the properties of MT such as wettability, glue penetration, bonding strength, etc., and discuss the future of the field.
•Numerous opportunities that exist for mass timber in construction were given.•The implementation of current wood protection protocols to mass timber was explored.•The pros and cons of mass timber protection were discussed.•Further recommendations on evaluating the durability of mass timber were given.•The impacts of treatment on the properties of MT were discussed.
Wood modification using polyesterification of sorbitol and citric acid is a novel environmentally friendly strategy for wood protection improving its dimensional stability and acts against fungal ...deterioration. Inelastic Raman scattering is sensitive to the molecules of high polarizability and both lignocellulose and aliphatic esters formed during the treatment are polar. Therefore, in the present study, the quality control of the treatment using a handheld Raman spectrometer equipped with 830 nm laser is suggested as a rapid and reliable approach. Raman spectra from six wood modification levels (resulting in different weight percent gain, WPG) of three different wood species (Silver birch, Scots pine and Norway spruce) as well as three sample preparation strategies (intact, sanded and milled wood samples) were collected, and further analyzed using a chemometric method. Best performing models based on Powered Partial Least Squares Regression predicted the WPG level at R2 = 0.85, 0.95 and 0.98 for birch, pine and spruce, respectively. In addition, a clear separation between hard and soft wood species was also captured. Especially for softwood species, the sample preparation method affected the model accuracy, revealing the best performance in milled material. It is concluded that by using handheld Raman spectrometer it is possible to perform accurate quality control of wood modified by polyesterification of citric acid and sorbitol.
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•A quick and accurate quality control is required for broad application of wood protection using sorbitol and citric acid.•Handheld Raman spectrometer is a promising tool for quality control of wood treated with citric acid and sorbitol.•Chemometric modeling allows to predict the weight percent gain (WPG) level with high accuracy for birch, pine, and spruce.•The sample preparation method affected the model accuracy, with milled material performing the best for softwood species.
Wood modification can be broadly categorized into chemical and physical processes, with acetylation and heat treatment being two of the most common methods in each category, respectively. This study, ...for the first time, combines these two modification methods and investigates the effects of high-temperature vapour-phase acetylation (HTVPA) on the physicomechanical properties of Japanese cedar (Cryptomeria japonica) wood in the temperature range of 145 to 220 °C for 2 to 16 h. Additionally, the acetylation variations within the wood were evaluated. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and near infrared spectroscopy (NIR) spectral analysis showed that the hydroxyl group of Japanese cedar wood reacted with acetic anhydride to form an acetyl group by HTVPA process. When the HTVPA temperature was 220 °C, dehydration and deacetylation of wood occurred. Furthermore, based on the weight percent gain (WPG) and physicomechanical properties of the treated wood, the 200 °C/8h was considered the optimal HTVPA treatment condition. The profiling analysis results showed that the acetylation depth in the longitudinal direction was 40 mm, while the depth in the tangential and radial directions was 3–4 mm. However, the theoretical WPG of the surface of HTVPA treated Japanese cedar wood was 30.0–31.6 %.
Wood is a versatile and renewable resource utilized in a wide range of applications, including tools, furniture, construction, and advanced engineering structures. However, certain inherent ...properties of wood, such as moisture and ultraviolet (UV) degradation, impose limitations on its long-term durability and dimensional stability for outdoor applications. This research investigates the weathering durability of cross-laminated timber (CLT) blocks surface-treated with titanium dioxide (TiO2) nanoparticles synthesized via liquid-precursor flame spray pyrolysis (FSP), directly deposited onto the surface of CLT blocks, and thereby resulting in a porous TiO2 coating. This coating endows the CLT surface with superhydrophobic properties evidenced by a water contact angle of ≥150°. Results from scanning electron microscopy and X-ray diffraction show the coating to be comprised of crystalline, sub-100 nm individual and aggregated TiO2 particles with significant porosity. Even after an 8-week accelerated weathering test, a portion of the crystalline TiO2 particles remains on the CLT surface. The TiO2-treated CLT demonstrates enhanced resistance to discoloration and gloss change over 8-weeks of accelerated weathering conditions, which are evidenced by a total color difference (ΔE) that is 3–4 times lower than that of the untreated CLT in the initial two weeks, and 58% lower after 8 weeks of weathering. Furthermore, the TiO2-treated CLT exhibits fewer weathering defects, such as splits and cracks, than the untreated CLT. The enhanced weathering durability of the TiO2-treated CLT is attributed to reduced lignin degradation, which is supported by the Fourier-transform infrared spectroscopy analysis. The findings of this study suggest that the TiO2 coating by FSP offers a viable and cost-effective method for modifying engineered wood products for improving hydrophobicity and protecting against the deteriorating effects of UV irradiation and moisture exposure.
•TiO2 nanoparticles are applied to the surface of CLT blocks by flame spray pyrolysis (FSP).•The FSP process on CLT results in a TiO2 layer consisting of sub-100 nm TiO2 nanoparticles on CLT.•TiO2-treated CLT shows enhanced resistance to discoloration and weathering defects during an 8-week accelerated weathering test.•Enhanced protection against lignin degradation is attributed to the UV-absorbing properties of TiO2 nanoparticles.
Wood is an irreplaceable structural and biodegradable material, which is subject to swelling, shrinkage, significant deformation of structural elements, and products when its moisture content ...changes. This paper proposes wood surface modification with reactive copolymers based on glycidyl methacrylate and alkyl methacrylates to impart superhydrophobic properties with initial contact angles up to 166°. Scanning electron microscopy and energy dispersive X‐ray spectroscopy were used to study the features of polymer coating formation and to determine the modifier penetration depth, which was more than 1000 μm. It has been shown that copolymers do not fill the initial capillary system of wood. Modified wood is characterized by stable water‐repellent properties with low‐water diffusion rates, with the water absorption rate reduced by more than three times compared to that of initial wood. Polymer coatings provide water repellency, retain the appearance of original wood, and provide increased buoyancy.
This paper describes an approach to address the issue of increasing water resistance of wood based on impregnation modification using special reactive hydrophobic copolymers. Impregnation modification preserves the original appearance and characteristics of wood, with the modifier in the near‐surface layer allows to achieve a superhydrophobic condition with initial contact angles up to 166° with long‐term water‐repellent properties
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