AbstractIonic liquids (ILs) are being increasingly explored as extraction solvents due to their tunable properties, which can control their ability to dissolve an array of solutes. IL selection requires an in-depth understanding of the consequences of IL structure on extraction outcomes for different substrates. Here, 14 ILs containing cations and anions that have been systematically modified to examine key structural effects have been explored for the extraction of chemical components from Pinus radiata bark. The extraction efficiency relative to the mass of bark ranged from 4 to 70%, and the isolation of bark components was evaluated using antisolvent addition. Extraction outcomes highlighted the importance of the IL anion in affecting extraction efficiency and selectivity, with a secondary role from the IL cation, and point toward a simple route for improving the overall selectivity of biomass extractions through control of the antisolvent addition process.

AbstractIt is necessary to delignify wood samples and treat them with ethylene diamine (EDA) before they are dissolved in 8% (w/v) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) prior to size-exclusion chromatography (SEC) analysis. In the present study, the effects of delignifying birch wood powder 0–3 times with NaClO2 and subsequently treating it with EDA on its solubility in 8% (w/v) LiCl/DMAc and its SEC data. The neutral sugar composition of the birch powder was almost unaffected by either delignification or treatment with EDA. Treatment of the birch powder with EDA resulted in 28% solubilities in 8% (w/v) LiCl/DMAc. Approximately 11% of cellulose molecules in the birch wood powder was dissolved, and detected as a high-molar-mass (HMM) fraction in the SEC elution pattern. Each single delignification treatment increased the solubility in 8% (w/v) LiCl/DMAc to 68–74% after EDA treatment. Based on the glucose contents of the delignified samples, almost all cellulose molecules in the delignified samples were dissolved in 8% (w/v) LiCl/DMAc after EDA treatment, and detected as the HMM fractions in the SEC elution patterns. The HMM cellulose molecules in the EDA-treated birch powder had linear random-coil conformations in 1% (w/v) LiCl/DMAc. However, the SEC data suggest that there probably were some chemical linkages between the HMM cellulose molecules and lignin or NaClO2-treated lignin fragments in the HMM fractions.

AbstractA mesoporous porous carbon (PC-KOH + Urea) with ultra-high specific surface area (SSA) was prepared from steam exploded poplar through urea-assisted KOH activation. The obtained PC-KOH + Urea had an ultra-high SSA of 3316 m2 g−1 and a total pore volume (VT) of 1.96 cm3 g−1, much higher than that of PC-KOH and PC-Urea, produced by KOH and urea activation alone, respectively. Meanwhile, PC-KOH + Urea possessed extremely high mesopores surface area (Smeso) (2183 m2 g−1) and mesopore volume (Vmeso) (1.46 cm3 g−1). In addition, urea can also serve as nitrogen source to dope nitrogen into PC-KOH + Urea, resulting in nitrogen content of 3.29%. To study the effects of urea on pore-forming, thermogravimetric analysis (TG) and thermogravimetric infrared technology (TG-IR) were adopted. It can be assumed that the ultra-high SSA of PC-KOH + Urea was mainly attributed to the reactions between pyrolysis products of urea and carbon. With ultra-high SSA, mesopore-dominated structure, and nitrogen doping, PC-KOH + Urea exhibited a high specific capacitance of 335.3 F g−1 at current density of 0.5 A g−1 in 6 M KOH aqueous electrolyte. In cyclic stability measurement, the capacitance retentions of PC-KOH + Urea were 99.6% after 4000 cycles. Thus, urea-assisted KOH activation was a feasible method to produce porous carbon with excellent performance.

AbstractEucalyptus globulus is an important pulpwood source due to favorable wood characteristics, including low extractive content. However, there is significant tree-to-tree variation that can be exploited in breeding. This requires screening a large number of samples, which NIR and PLS-R make possible. Models are typically developed for a specific set of samples prepared in the same way. The question is: how well these models predict samples that are different from the ones used in the model. Models developed to determine the extractive content of Eucalyptus globulus wood from Australia were used to E. globulus wood from Argentina, which differed in age and sample preparation. The main difference between spectra of the two origins was in the OH combination band, despite the fact that samples were dried identically. Due to this difference, models that included the O-H band assigned above 73% of the spectra as outliers regardless of preprocessing, whereas models that did not include the O-H band assigned fewer spectra as outliers. The differences in the OH band were attributed primarily to differences in particle size and extractive content, rather than to differences in humidity content. However, all models predict similar results for all samples, including outliers.

AbstractIn order to develop a new wood product suitable for outdoor applications, a high melting point polyethylene wax was used for high-pressure impregnation treatment of wood. Properties of impregnated wood were studied. Wax in molten state was stable with low viscosity, good fluidity, and easily penetrate into the wood under high pressure. Full-cell process included vacuum (-0.06 MPa for 30 min), high-pressure impregnation (0.75 MPa for 3 h) and pressure release (30 min). Wax contents of treated lodgepole pine (Pinus contorta Douglas ex Loudon.) and eucalyptus (Eucalyptus saligna) were 0.205 g/cm3 and 0.321 g/cm3, respectively. Cell gaps and cell cavities of wood were filled with polyethylene wax. Nanoindentation tests showed that longitudinal mechanical properties of wood cell walls were weakened after impregnation. After a 3 h high-pressure impregnation, hardness of lodgepole pine wood cell walls was reduced by 35.1%, and the modulus of elasticity was reduced by 4.9%. Treated wood had a much lower water absorption and swelling rate than untreated wood, its weathering resistance as well as insect resistance were better.

AbstractThis current study aims to extract bamboo fibers from different species of bamboo using the mechanochemical method and investigate their properties. The bamboo species used in this study were Dendrocalamus, Bambusa balcoaa, Oliveri, Asamica, and Chimono. The vacuum-pressurized impregnation treatment process was employed for treating the bamboo. The mechanochemical method was chosen for extracting the bamboo fibers due to its simplicity and efficiency. The yield percentage of the bamboo fibers was determined. X-ray diffraction (XRD) analysis showed an increase in the crystallinity of the bamboo fibers with subsequent treatments in the presence of NaOH, as evidenced by two well-defined peaks at 2θ = 17.6° and 2θ = 22.7°. FTIR analysis revealed the presence of numerous hydroxyl groups in the bamboo fibers, indicated by the –OH expanding and contracting vibration at the band around 3311 cm−1. Thermal gravimetric analysis (TGA) was conducted to investigate the thermal stability of the bamboo fibers, and the results demonstrated that chimino bamboo fiber exhibited the highest level of thermal stability compared to other treated bamboo fibers. Scanning electron microscopy (SEM) was employed for morphological characterization, providing insights into the surface morphology of the bamboo fibers. Based on the findings, it can be inferred that bamboo fibers, particularly of the chimino type, have the potential to serve as a viable reinforcement in polymeric composites for lightweight applications in various industries, such as automotive, aerospace, and packaging.

AbstractInteractions between the hierarchical structure of Japanese cypress and small hydroxylic solvents with high polarity were studied using variable-temperature 13C cross-polarization and magic-angle spinning nuclear magnetic resonance (CP/MAS) NMR spectroscopy, including low-temperature measurements. 13C CP/MAS NMR spectra were enhanced by dipolar interactions closely related to 1H–13C magnetization transfer, providing information about the interaction between woody materials and small hydroxyl molecules. The change in interaction was particularly near the melting point of the hydroxylic solvent, where a decrease in the intensity of the cypress carbohydrate signal and the appearance of the signal of solvent molecules were observed. The trend of signal intensity in the variable-temperature 13C CP/MAS NMR spectra of cypress and cellulose fibers in the presence of hydroxylic solvents indicated that the decrease in the carbohydrate signal intensity due to the transfer of magnetization near the melting point of the hydroxyl molecule is greater when the size of the hydroxyl molecule is smaller. Furthermore, molecular association in the nanopores of the hierarchical structure allowed the hydroxyl molecular signals of the impregnated cypress to appear above the melting point.

AbstractThe main goal of this study was the elucidation of structures of products of oxidation of industrial hydrolysis lignin (HL) obtained in the system H2O2-H2SO4-H2O. It was found that the obtained oxidized hydrolysis lignin (OHL) contained structural fragments of muconic acid dilactone. The latter appeared as a result of the oxidation of aromatic ring of HL into unstable structures of 3,4-dihydroxyadipic acid, which are spontaneously cyclized into the corresponding fragments of muconic acid dilactone in acidic oxidative medium. Consequent reaction of OHL with aqueous sodium hydroxide (NaOH) led to the formation of sodium salt of OHL (Na-OHL), in which the muconic acid dilactone units of OHL opened into fragments of disodium salts of 3,4-dihydroxyadipic acid. The Na-OHL was transformed into the series of novel derivatives of lignins. Thus, the reaction of Na-OHL with thionyl chloride proceeded as a substitution of hydroxyl groups into chlorine atoms in the structure of OHL, that afforded chloro-derivative of OHL. The latter was transformed into amino-amide and ester-ether derivatives of OHL by nucleophilic substitution of chlorine atoms with amines and alcohols correspondingly.

AbstractDetermination of the chemical composition of biomaterial is important for their valued utilization in biorefinery. In this study, the chemical composition of five bamboo species, i.e., mitinga (Bambusa tulda), borak (Bambusa balcooa), rengoon (Thyrsostachys oliveri), orah (Dendrocalamus longispathus), and bajja (Bambusa vulgaris) were determined. The chemical characterization of these bamboo species can expedite a further study on the extraction of cellulose and lignin. α-cellulose content was in the range of 42.7–45.7% and Klason lignin content was 22.4–28.2%. The ash content was 1.8–4.3% for the studied five bamboo species. The α-cellulose and lignin content were similar to other non-timber spices. The ash content was lower than other non-timber species. Therefore, these species can be a potential source of raw material for biorefinery.

AbstractThe dilemma of insufficient wood resources and poor properties of fast-growing wood necessitates a breakthrough in the expansion and efficient utilization of wood resources to meet the real needs. With the aim of enhancing the properties of fast-growing poplar wood, a combination of PVA and nano-silica sol impregnation treatment was carried out to develop a novel functional wood material with good dimensional stability, compressive strength and thermal stability, while fully exploiting the unique structural properties of the wood itself. In this work, PVA-nano-silica sol composite wood was prepared by in-situ impregnation of poplar fast-growing wood via ultrasound-assisted and vacuum impregnation methods. Firstly, the effects of different treatments on the impregnation effect and strengthening effect of modified wood were explored. The results showed that the PVA-nano-silica sol dispersion system had no negative effect on the impregnation modification, and the compressive strength of modified wood was obviously improved compared with natural wood. Among them, the most effective modification was achieved under the condition of vacuum-assisted impregnation. The effect of compound impregnation modification on the structure of poplar fast-growing wood was analyzed by FTIR, XRD, SEM, and EDS, in which PVA and nano-silica sol can form a certain cross-linking system and form chemical bonds such as Si-O-C and Si-O-Si, enabling them to enter the structure of wood and react with wood cell walls effectively. The compressive strength of modified poplar wood was increased by 72.29% compared with natural poplar wood. According to the thermogravimetric analysis, the thermal stability of the modified poplar wood was improved to some extent. In view of all the results, the method proposed in this study provides an opportunity for the high value utilization of low quality wood, and this modified wood can be considered as a candidate for new lightweight and high performance materials in the construction field.

AbstractThe re-profiling from paper-grade to dissolving pulp production is a common trend for acid sulfite cooking of wood. This provides substantial changes in the composition of the spent sulfite liquor (SSL) affecting its potentialities in subsequent processing within the biorefinery concept. In this work, a comparative analysis of the chemical composition of SSL was performed from the magnesium-based acid sulfite cooking of Eucalyptus globulus wood to produce the paper-grade and dissolving pulps. More severe pulping conditions required for dissolving pulp production led to a substantial increase in volatile compounds in SSL, such as acetic acid, methanol, and furfural. At the same time, the amounts of dissolved sugars and lignosulfonates (LS) were increased to a less extent. The main changes detected in LS were related to the increase of its molecular weight, degree of condensation, and sulfonation degree. The increased concentration of the sulfuric acid in SSL was one of the reasons for these changes.

AbstractIncreasing concerns toward climate change and fossil fuel-based products have opened the race toward viable alternative feedstocks, which could be utilized as alternatives for omnipresent chemicals such as fuels and polymers. Lignin is among one of the most promising candidates. Besides its promising chemical characteristics, it has also been put in the spotlight due to its economic potential for biorefinery profitability and waste reduction. As the timber industry has to fight a constantly growing larch bark by-product stream we decided to investigate its potential capacity as valuable source of biopolymers. Deep eutectic solvents due to their biodegradability, reusability and efficiency have been chosen as the extraction method of choice. The reaction parameters were optimized resulting in a very high lignin yield of 93%. Furthermore, the work-up process was investigated with a focus on quantitative chemical recycling and potential for upscaling to industrial scale.

AbstractThis study aims to investigate the sugar components which play an important role in the process of heartwood formation in young Swietania mahagoni. The methanol-water (70/30, v/v) extract was analyzed by GC-MS to determine sugar constituents. The content of methanol-water extract ranged from 3.7 to 7.8% based on dried wood. After a 4-5 year duration of heartwood formation in the sapwood, monosaccharide and alditol fractions doubly increased. This was followed by almost five times the content of cyclitols. In a radial variation, the content of major monosaccharides including fructose, glucose, mannose and xylose decreased from sapwood to heartwood, while arabinose, galactose, and sucrose in the age 5 years were only found in the sapwood. Meanwhile, the main content of cyclitols and alditols (arabitol) significantly decreased from sapwood to heartwood. The main monosaccharides and disaccharides represented by sucrose played a key role in the process of heartwood formation. Further studies are required to investigate the phenolic and lipophilic components as both are involved in heartwood formation. In addition, similar studies on alditol and cyclitol regarding their role in tropical wood are necessary.

AbstractSpalted heartwood is valued for its vibrant colors, patterns, and decay-free appearance. Using microscopy, scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and non-targeted metabolomics, we aimed to study some distinctive features of black patterning. The results showed that cocci might be associated with the production of spalted heartwood. There was an absence of decay in the spalted heartwood because the cocci had not aggressively attacked the cell walls. 4-pyridoxine, often associated with the bacterial stimulation of organisms, was identified as an upregulated metabolite in the black-patterned wood compared to non-colored areas. We identified four primary metabolic pathways related to bacterial activity associated with the black patterning: pentose and glucuronate interconversions, ATP-binding cassette transporters, histidine metabolism, and plant hormone signal transduction. These results suggest that microbes might play a significant role in the development of the heartwood’s distinctive black pattern in Diospyros spp.

AbstractParticleboards produced with other lignocellulosic materials, beyond wood, are promising products for the furniture and building construction components, as doors, lining, floor, partitions, and coverings. However, there is little information about the resistance of them to xylophagous organisms. This is important due the different uses of particleboards, where they will be subject to attacks by decaying organisms, which can affect a structure and put people at risk. The present study aims to determine the biological resistance of particleboard produced with pine, sugarcane bagasse and malva particles to xylophagous organisms. The particleboard was produced with different proportions of pine wood heat treated at 200 °C and malva fiber (outer layers) and sugarcane bagasse core glued with an adhesive based on polyurethane from castor oil. No-choice and choice feeding tests with dry wood (Cryptotermes brevis) and conehead (Nasutitermes corniger) termites were carried out for the resistance test to xylophagous organisms, in addition to a test with rotting fungi which cause brown (Gloeophyllum trabeum and Rhodonia placenta) and white rot (Irpex lacteus and Trametes versicolor). The trial with dry wood termites showed low mass losses, regardless of the proportions applied. The mass losses were accentuated for the test with conehead termite, having the particleboard composed of 100% pine been the most resistant among the boards tested. The greatest mass losses for fungal resistance were caused by Gloeophyllum trabeum. The particleboard produced with 100% pine (outer layer) showed the highest resistance to the tested xylophagous organisms.

AbstractNear Infrared Spectroscopy (NIR) is often used to perform high throughput phenotyping on thousands of genotypes using prediction models with high variability. A study was therefore undertaken to analyze the potential of multispecies, multisite and multi-age NIR calibration models of seven chemical properties of eucalyptus wood. The models are based on 358 samples selected among more than 5000 samples that belong to five eucalypt species including hybrids. The samples were collected from trees aged 2-35 originating from four different countries. Spectra were measured on non-extracted wood powders using an FT-NIR spectrometer. Models were established in the spectral range of 9090-4040 cm−1 using the PLS regression method, tested by repeated cross-validation and validated on independent test sets. The results showed that the robust models for total extractives (R2P = 0.91, RMSEP = 1.20%, RPD = 3.3) and KL (R2P = 0.89, RMSEP = 1.21%, RPD = 3.0) provided good predictions. These two properties were the best predicted, followed by the S/G ratio (R2P = 0.84, RMSEP = 0.19, RPD = 2.5) and ASL content (R2P = 0.81, RMSEP of 0.54, RPD = 2.3). For holocellulose, alphacellulose, and hemicelluloses contents, the models provided approximate predictions. The prediction errors were always less than twice of the laboratory errors except for ASL and S/G ratio. For total extractives and ASL, β-coefficients of models were of approximately the same magnitude throughout the 9000-4000 cm−1 region while for the five other properties, they were higher in the 7500-4000 cm−1 region. Models were also established in narrower NIR regions, and the quality of models obtained was about the same as that of the models based in the 9090-4000 cm−1 wide range. These established robust models can be used to make predictions based on samples of high variability.

AbstractRaw hemp (Cannabis sativa L.) was subjected to alkaline delignification with the application of NaOH ranging from [0.125M] to [1M] for times from 5 to 480 min. Lignin contents of the original and delignified samples were determined. The samples were subjected to thermogravimetric analysis (TGA) under a N2 atmosphere with temperatures ramped from 25 to 600 °C at 10 °C min-1. Lignosulfonates samples of low, medium and high molecular weight were subjected to the same TGA and showed that lignin decomposed over the entire temperature range. The contributions of lignin to the mass loss during thermal decomposition of hemp and kinetics of lignin content and the most relevant TGA results were determined. Regression models estimating the lignin content of the fibers based on TGA results were formulated. These models allow for the prediction of mean lignin content within ± 0.1% (based on dry weight of pulp) in the central range of the experimental field.

AbstractThree-dimensional hydrophobic and efficient electromagnetic shielding Cu/wood/Cu laminated composites were prepared by a simple one-step electroless Cu process. The number of electroless Cu on wood surface and the treatment time of electroless Cu were used as variables. The effects of independent variables in the range from 0.3 ×10−3 to 3.0 GHz (L-band) on the conductivity, water contact angle and electromagnetic shielding effectiveness of the composite were analyzed. The Cu particles are fully filled in the wood hierarchical porous structure, and the metal coating uniformly covers the entire wood surface. After three times of electroless Cu, the conductivity of the composite can reach 7255 S/cm, the contact angle is 130.8° when the time is 12 min, showing good hydrophobic properties, and the average electromagnetic shielding effectiveness is as high as 96 dB. Compared with the L-band (94 dB), the twice electroless sample has a maximum shielding effectiveness of 85.6 dB in the X-band (8.2-12.4 GHz), which can shield a large number of incident electromagnetic waves to achieve high absorption and low reflection. The anisotropic internal porous structure of wood matrix and the multi-interface polarization between wood and Cu are the main reasons for the effective electromagnetic interference shielding performance of Cu/wood/Cu laminated composites.

AbstractDue to increasing environmental awareness, in recent years the research on classical wood preservation by hazardous impregnation chemicals has been shifted to more environmentally friendly chemical modification methods with organic molecules/polymers. The chemical modification processes rely on the replacement or blockage of wood hydroxyl groups with generally hydrophobic molecules, thereby improving the dimensional stability, water repellency and biological resistance of the wood. This study investigates in situ polymerization of ε-caprolactone to form poly(ε-caprolactone) (PCL), a biodegradable polymer, which was grafted to the wood cell walls of both Scots pine (Pinus sylvestris L.) and spruce wood (Picea orientalis L.). Wood modification by in situ polymerization of ε-caprolactone has been studied so far in order to be an alternative modification approach to obtain improved wood properties, such as good dimensional stability and improved water resistance without reducing mechanical properties considerably. In the light of previous studies, the current work proposes a methodological approach to ε-caprolactone modification in two aspects: (i) the effect of catalyst (tin(II) 2-ethylhexanoate) amount on wood properties (i.e., swelling (S), anti-swelling efficiency (ASE), water uptake (WU), mass loss (ML)) (ii) the effect of oven or solvent curing of ε-caprolactone on wood properties (i.e., S, ASE, WU, ML, compressive strength parallel to the grain, and chemical components). By these approaches, an optimum catalyst amount was determined, and an alternative method (oven-curing) which may be more economic by enabling the re-use of the waste chemical was evaluated in comparison to the method of ε-caprolactone modification in prior publications (solvent-curing).

AbstractRotation welding of wood dowels has the advantages of high bonding strength, fast processing speed and green environmental protection, and is suitable for jointing nodes in furniture and wood products. However, most wood friction welding specimens have poor water resistance where the welded joints are more likely to be damaged in wet environments, which greatly limits their wider application. Previous studies focused on using natural and green materials or methods to enhance bonding strength and water resistance of friction-welded joints. This paper reveals an innovative chemical pretreatment method to improve the water resistance of rotary friction welded joints by treating the substrate blocks or dowels with reagents that successively oxidize and sulfonate the wood, and spraying the dowels with Zinc acetate alcohol solution that has a lubricant effect, followed by friction welding. The findings show that both the dry bonding strength of friction welded joints and the wet bonding strength after impregnation with cold, hot, and boiling water of dowels pretreated with oxidation and sulfonation reactions were higher than those without pretreatment and significantly superior to the traditional polyvinyl acetate (PVAc) adhesive bonding.