Abstract This study examines the impact of precipitation conditions, specifically pH and temperature, on the production of Eucalyptus kraft lignin from black liquor, focusing on the resulting chemical properties. Additionally, the process of hydroxymethylation of lignin during precipitation in a single step was investigated. Lignins were characterized using wet chemical analyses, which included the determination of phenolic hydroxyl group content, carboxylic group content, syringyl-to-guaiacyl ratio, molecular weight distribution, and glass transition temperature. Additionally, ATR-FTIR spectra were recorded, and prediction models between these spectra and lignin descriptive parameters were established: phenolic OH content, carboxyl group content, S/G ratio, glass transition temperature, and molecular weight distribution. The results demonstrate that the properties of the precipitated lignin are influenced by both pH and temperature during precipitation, with the precipitation yield exhibiting the most pronounced variation. The study also concludes that lignin activation during precipitation is achievable, with the most favourable outcomes observed at pH 9 and 80 °C.
Abstract TiO 2 was magnetron-sputtered on wood to achieve ultraviolet (UV) resistance and photocatalysis. In this study, Populus tomentosa Carr was used as the substrate. The wood was treated with either polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS), then deposited nano-TiO 2 films onto their surfaces via magnetron sputtering to fabricate nano-TiO 2 -coated wood. The microstructure, surface morphology, ultraviolet aging resistance, and photocatalytic performance of the nano-TiO 2 -coated wood samples were systematically characterized. The results show that after 90 min of magnetron sputtering, smooth, continuous, and dense amorphous nano-TiO 2 films were formed on both TiO 2 /PVA/wood and TiO 2 /PDMS/wood surfaces, with Ti mass fractions surface were 35 wt% and 38 wt%, respectively. After 110 h accelerated UV ageing, the total color differences (Δ E* ) of TiO 2 /PVA/wood and TiO 2 /PDMS/wood were 6.43 and 3.79, corresponding to 76 % and 87 % reductions compared with unsputtered sample, indicating excellent light stability. After 120 min of UV irradiation, methylene blue was catalytically degraded to 65 % and 48 % of its initial concentration, demonstrating good photocatalytic activity. In summary, magnetron sputtering deposition of nano-TiO 2 onto wood produces functional wood materials with enhanced UV aging resistance and photocatalytic properties. This work provides new insights for wood functional modification, indoor air purification, and green building material applications.
Abstract Porodaedalea chrysoloma (Fr.) Fiasson et Niemelä is a basidiomycete that causes pitting white rot in conifer trees such as Japanese larch, leading to significant losses in wood density and mechanical strength. Consequently, the utilization of decayed wood is severely limited in the wood industry. Herein, furfurylation was applied to improve the properties of white pocket-rot wood, particularly its density and dimensional stability. The furfurylation process involved the maleic anhydride followed by the polymerization of furfuryl alcohol (FA) under vacuum impregnation. Fourier transform infrared spectroscopy confirmed that FA was impregnated into the white pocket-rot samples and polymerized in situ within the cell walls. In the early stages of decay, furfurylation resulted in a higher mass percent gain (86.2 %–181.3 %) than in sound wood. As the decay-area ratio increased, the mass change of the furfurylated wood also increased. Additionally, furfurylation enhanced anti-swelling efficiency, and reduced water absorption, even after extraction of untreated FA. These results suggest that the pore structure formed facilitates the penetration of both the acid catalyst and FA, thereby improving furfurylation efficiency in decayed wood. This study provides new insights into the potential for upgrading decayed wood by combining the decay characteristics of white pocket rot with furfurylation.
Abstract Bambusicolous fungi play crucial roles in bamboo growth, health, disease, and lignocellulose decomposition. Among them, Apiospora species occupy diverse ecological niches as endophytes, pathogens, and saprotrophs. Fungal decay ability is an important functional trait for understanding ecological roles and substrate utilization strategies. Therefore, this study aimed to evaluate the decay activities of nine bambusicolous Apiospora species on Phyllostachys bambusoides and Phyllostachys nigra var. henonis and to determine whether decay ability is associated with ecological lifestyle. Chemical composition analyses and transmission electron microscopy (TEM) were conducted to characterize substrate-specific degradation patterns and cell wall decay. All tested Apiospora species exhibited measurable decay activity with substantial interspecific and substrate-dependent variation. Apiospora rasikravindrae demonstrated the highest decay activity on both bamboo species, whereas Apiospora hysterina and Apiospora sargassi consistently showed low decay performance, suggesting functional differentiation associated with distinct ecological strategies. Several species exhibited moderate decay activity on P. bambusoides ; however, their decay efficiency was markedly reduced on P. nigra var. henonis , while Apiospora saccharicola displayed the opposite pattern. Chemical analyses and TEM observations confirmed degradation patterns consistent with soft-rot decay. These results demonstrate substantial functional diversity among bambusicolous Apiospora species and provide new insights into their ecological roles in bamboo decay.
Non-destructive quantification of the internal progression of thermally induced degradation in wood using X-ray imaging is challenging because the material is inherently heterogeneous and the resulting intensity changes are small, spatially variable, and influenced by acquisition noise and partial-volume effects. A measurement framework was developed for quantifying combustion-front penetration in wood using time-resolved X-ray computed tomography (CT) during controlled one-sided heating. The focus was on defining and measuring the combustion front in CT data rather than detailed physical interpretation of underlying material transformations. A CT-compatible heating arrangement enabled repeated volumetric scanning without interrupting thermal exposure. An automated voxel-wise analysis pipeline was implemented, including baseline normalisation using robust median-based statistics, formation of depth-dependent profiles along the heating direction, and threshold-based front detection with sub-voxel interpolation. Measurements were evaluated within a fixed three-dimensional region of interest located approximately 10 mm inside the specimen boundaries to reduce edge effects and ensure reproducible spatial sampling. Validation against post-exposure visual assessment showed reliable front detection only when a statistically coherent volumetric signature was present. Application to a dynamic experiment enabled extraction of a representative propagation rate of 0.92 mm min-1.
Abstract Internal moisture and temperature of wood significantly affect its electrical resistance, destabilizing electrical resistance tomography (ERT) accuracy in log knot detection. To address this, this paper investigates the eccentric circle search-based inverse distance weighting (ECIDW) algorithm, based on the shortest current path model, under varying temperature and moisture gradients. ERT experiments on four Chinese fir ( Cunninghamia lanceolata (Lamb.) Hook.) logs (No. 1–No. 4) revealed a significant nonlinear coupling effect between environmental factors and imaging quality. Compared to extreme conditions, a specific window drastically improves accuracy. An optimal relative humidity of 60 % effectively suppresses cavitation and uneven moisture artifacts, maintaining area prediction errors for specimens No. 1, No. 2, and No. 4 within 25 %. Concurrently, an optimal temperature of 20 °C balances thermal activation responses; it sharply reduced the error of specimen No. 4 from 53.7 % at 10 °C to 6.3 %, and prevented feature collapse in No. 2 at 25 °C. Ultimately, operating within this optimized 20 °C and 60 % relative humidity window allows the ECIDW algorithm to significantly reduce background noise, improve the signal-to-noise ratio, and accurately predict knot position, area, and shape in Chinese fir logs.
Major phenolic extractives were quantified in heartwood and sapwood from a 20-year-old Quercus robur progeny trial in southern Denmark, selecting individuals with contrasting heartwood content. Acetone-water extracts were analysed by HPLC-UV for vescalagin, castalagin, and ellagic acid, and by Folin-Ciocalteu for total phenolics. Across groups with low, intermediate, and high heartwood absolute content, mean concentrations of quantified ellagitannins were similar and no group differences were detected. Within the environmental context of this Danish trial and the present sample size, increased heartwood production was not associated with lower concentrations of the quantified extractives. These results support breeding strategies targeting higher heartwood yield without an apparent penalty in ellagitannin content in newly formed heartwood.
The drying of eucalyptus wood involves coupled shrinkage and collapse driven by capillary tension and drying stress. This study investigated shrinkage in Eucalyptus urophylla & times; E. grandis using 2-mm and 5-mm fiber-direction specimens dried at 45, 65, and 85 degrees C, to elucidate the interactive effects of temperature and thickness on moisture migration and shrinkage. Two-way ANOVA showed that both temperature and thickness significantly influenced drying rates (p < 0.001), with a significant interaction (p < 0.001). The drying rate of 2-mm specimens was 2.9-6.6 times higher than that of 5-mm specimens at the same temperature. The 2-mm specimens dried at 45 degrees C exhibited the smallest internal moisture content (MC) gradient (8.5 %), resulting in minimal drying stress. Greater collapse occurred in 5-mm specimens at higher temperatures. Below the fiber saturation point (FSP), shrinkage and MC showed a strong linear relationship (R-2 > 0.98). However, the apparent FSP estimated by regression increased with temperature (from 23.2 % to 32.1 %), reflecting the confounding effects of collapse and drying history. Among all conditions, the 2-mm specimens at 45 degrees C exhibited the smallest MC gradient and least evidence of collapse, suggesting that their shrinkage behavior most closely approximated free shrinkage conditions among the tested treatments.
To resolve the surface color variance and cracks in heat-treated wood induced by environmental factors such as light and water, the magnetron sputtered coating method was used to modify heat-treated wood in this study. The effects of four modification strategies in terms of pure PDMS (polydimethylsiloxane), pure magnetron sputtering ZnO, PDMS-ZnO (PDMS coating followed by ZnO sputtering), and ZnO-PDMS (ZnO sputtering followed by PDMS coating) on the wettability and anti-aging properties of heat-treated wood surfaces were compared. The morphology and chemical composition of the modified wood before and after aging were studied using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy to reveal the modification mechanism. The results showed that the four coatings were successfully loaded onto the wood surface. After 360 h of artificial aging, the surface of the heat-treated wood coated with ZnO-PDMS retained its original structure with no cracks, warping, or other damages. The PDMS coating effectively prevented the invasion of wood by water and reduced the loss of the ZnO particles sputtered on the wood surface, thereby enabling ZnO to provide long-term UV shielding. After aging, the equilibrium contact angle reached 133 degrees, while the color difference (Delta E*) was 2.72, indicating good hydrophobicity and light-aging resistance.
Behaviour of cork structural components (suberin, lignin and polysaccharides) during ethanol-water treatments was studied with different temperatures (135-185 degrees C), times (53-187 min) and ethanol concentrations (0-100 %), using response surface experimental design. The severity factor combining temperature and time was calculated to indicate different severity conditions (SF 3.1 to 4.6). Extractive-free cork was autoclaved, and mass loss and chemical composition of cork were determined. Mass loss was small, increasing with severity: 3.9 % of cork for SF 3.1, 11.4 % for SF 4.6. The ethanol-treated cork contained soluble material in dichloromethane (DCM) resulting from suberin depolymerization that increased with severity: 1.0 % and 5.4 % of the treated cork for SF 3.1 and 4.6 respectively. Little chemical changes occurred, mostly restricted to the most severe conditions with suberin only decreasing 5 % and lignin 18 % in relation to their original amounts. ATR-FTIR spectra showed very similar chemical profiles between samples. Lignin composition by analytical pyrolysis remained unaltered. Modelling cork depolymerization using solid mass yield and DCM solubles showed very good fit. Overall cork demonstrated considerable stability in ethanol-water processes, confirming higher resistance compared to lignocellulosic materials. Suberin proved remarkably strong and moderate delignification occurred but not to an extent that could impart cork performance properties.
In the past, numerous simulations of the long-term performance of wood components undergoing moisture changes have exhibited unresolved discrepancies with reality, pointing to misconceptions about the underlying wood's physical nature. Those are due to an incomplete and inconsistent experimental picture regarding orthotropy, moisture dependence, and the interconnection of distinct rheological mechanisms. This study, conducted on a single, homogeneous Norway spruce stem, provides a comprehensive insight into the elastic, viscoelastic, plastic, and hygroresponsive behavior in the three main anatomical directions. All data are described by generally accepted models, with moisture-scaling functions provided for each parameter. The described campaigns extend well beyond the minimum required tests for orthotropic bodies. This enables a quantitative assessment of the loss of accuracy due to symmetry assumptions, such as orthotropy and compression-tension symmetry. The completeness of the data allows for identifying oversimplifications in state-of-the-art rheological models, as well as for finding opportunities to reduce future testing effort.
Traditional wood identification relies on manual anatomical analysis, which is subjective, inefficient, and difficult to scale to meet modern high-efficiency demands. Despite rapid advancements in computer vision, existing wood identification methods predominantly operate as 'black box' models, often failing to provide diagnostic evidence consistent with standard wood anatomy criteria. Among hardwood anatomical features, vessels represent the most distinct and stable characteristics. This study develops a multi-stage deep learning pipeline for the automated identification and quantitative analysis of key International Association of Wood Anatomists (IAWA) vessel features, spanning a sequence of tasks from porosity classification and semantic segmentation to vessel grouping recognition and morphometric measurement. This study systematically compared candidate models at each stage to construct an optimal workflow. Experimental results demonstrate that MobileNetV3 excelled in porosity and groupings classification, achieving accuracy of 90.0 % and 96.2 %. U-Net achieved 0.939 mIoU in vessel segmentation. Furthermore, SPD-Conv YOLOv11 model attained an mAP0.5-0.95 of 0.845 for vessel measurement, maintaining error rates for mean diameter and density at 6.5 % and 10.5 %. The system attained an 81.3 % accuracy in identifying IAWA codes based on 300 wood micrographs. This study presents an interpretable, automated framework for wood feature extraction.
The production of vanillin (4-hydroxy-3-methoxybenzaldehyde) via alkaline aerobic oxidation of lignin is a promising strategy for synthesizing low-molecular-weight aromatic compounds from biomass. One of the major pathways for vanillin formation in this process involves the non-oxidative elimination of vanillin from beta-O-4-type vanillin end groups formed through oxidative depolymerization of lignin. A previous study revealed that this elimination pathway competes with a side reaction leading to polymerization. To gain further insight into this side reaction, the alkaline degradation behavior of 4-(2-hydroxyethoxy)-3-methoxybenzaldehyde (HEV), a simplified model compound of the vanillin end group, was investigated. Under non-oxidative alkaline conditions (4.0 mol/L NaOH aqueous solution, 80 degrees C, N-2), HEV produced vanillin and its disproportionation products in relatively low yields (similar to 30 mol%), while yielding a group of main products with strong absorption at UV (220 nm). Based on NMR analysis, these products were found to possess alpha,beta-unsaturated aldehyde structures, suggesting degradation of the aromatic ring during the reaction. Upon prolonged reaction, these products gradually converted into high-molecular-weight components. Taken together, the results are consistent with a possible side reaction pathway at the vanillin end group involving nucleophilic addition of OH- to an acetal intermediate, followed by retro-aldol cleavage of the aromatic ring and subsequent polymerization of linear conjugated aldehydes.
In pursuit of sustainable alternatives to fossil-based materials, cellulose-based products, such as regenerated cellulose and cellulose derivatives, have attracted increasing attention. These materials offer biodegradability, biocompatibility, and a wide range of adjustable properties. However, their production relies on dissolving pulps, which are significantly more expensive than standard paper-grade pulps due to high raw material and processing costs. In this study, a potential route for converting standard bleached chemical pulps into more reactive cellulose was investigated, targeting applications in cellulose derivatives and regenerated materials. The method is based on acidic treatment followed by cold alkali dissolution and precipitation. Results show increased chemical reactivity and partial hemicellulose removal, suggesting a promising path toward low-cost alternatives to conventional dissolving pulp.
The prehydrolysis kraft process (PHK) is the most widely used industrial method for producing dissolving pulp. Wood prehydrolysis involves the removal of hemicelluloses before kraft pulping, enabling the production of high-quality dissolving pulp. The process performance can be controlled by adjusting the time and temperature parameters. This study evaluates the effect of prehydrolysis intensity on the unbleached pulp quality of eucalyptus clones used for dissolving pulp production. Five trees from two eucalyptus clones (Eucalyptus urophylla and E. urophylla & times; E. spp.), aged 3 and 5 years, cultivated in plantations located in Bahia, Brazil, were assessed. Hydrothermal pre-treatments were applied to wood chips under varying time and temperature conditions (P-factor) to study its effect on kraft pulping and unbleached pulp properties such as yield, Kappa number, viscosity, brightness, pentosan content, and crystallinity index. Increasing the severity of the prehydrolysis process reduced the Kappa number and pentosan content, alongside an improvement of up to 8.6 % in pulp brightness and 7.2 % in the crystallinity index. These findings demonstrate the efficiency of optimized prehydrolysis conditions for dissolving pulp production, particularly for a P-factor of 432.
Modification with citric acid and sorbitol (SorCA) or with pure citric acid (CA) both improve wood durability, yet the contribution of sorbitol remains unclear. Scots pine sapwood was treated with SorCA or CA at equal chemical loadings and exposed to Trametes versicolor, Coniophora puteana, and Rhodonia placenta in an EN 113-2 (2021) decay test. Mass loss caused by T. versicolor was low for all treatments. For C. puteana and R. placenta, mass loss decreased strongly with increasing treatment level. However, CA treated samples showed lower mass losses than SorCA treated samples at comparable weight percent gain (WPG) and comparable calculated CA-content, suggesting differences in reaction pathways within the wood matrix. Moisture contents determined after exposure differed markedly from values obtained in standardised water uptake tests. Across fungi and treatments, absolute water content increased with treatment level and was negatively associated with mass loss. It remains unclear whether this relationship indicates a causal link between moisture and decay, or is confounded by other mechanisms that increase decay resistance.
Understanding how anatomy shapes wood me chanics is essential for grading and breeding. This study develop an interpretable SHAP-based framework providing the first conditionally independent decomposition of anatomical effects on Chinese fir (Cunninghamia lanceolata) performance. To mitigate data scarcity, synthetic-data generated by three generative models were evaluated for correlation, distribution and prediction. Five machine learning models were trained on synthetic data to predict modulus of elasticity (MOE), modulus of rupture (MOR), and compressive strength parallel to grain (CSP). All generative methods produced realistic data, with Gaussian Copula per forming best. The best accuracy was achieved by CopulaGAN-XGBoost (MOE, 75%), Gaussian Copula-AdaBoost (MOR, 80%), and Gaussian Copula-Random Forest (CSP, 91%), out-performing models trained on real data (58%, 64%, 68%) SHAP analysis identified tracheid length (15.6%, 6.0%, 8.3%), wall thickness (13.8%, 12.6%, 75%), and microfibril angle (3.4%, 2.7%, 4.5%) as key traits, with microfibril angle showing the strongest interactions. Latewood versus early wood contributions were 24.1% versus 16.7% (Mu Omicron Epsilon), 16.6% versus 39.9% (MOR), and 18.1% versus 28.8% (CSP). Density was the most influential trait: strength (MOR, CSP) was driven by density and earlywood traits, while stiffness (MOE) depended on density and overall anatomy. These findings provide interpretable guidance for wood quality assessment, material grading and plantation improvement.
To clarify the variations in terpenoid composition due to bark development, bark extracts from three trees of Lindera umbellata var. membranacea were analyzed. Stem discs were collected at different heights from two trees (A and B) to assess the variation in terpenoid composition relative to bark thickness. The remaining tree (C) was used to examine radial variations in terpenoid composition from the inner bark to the periderm. Terpenoid composition and the enantiomeric ratio of linalool were analyzed using gas chromatography-mass spectrometry and gas chromatography-flame ionization detection. The terpenoid composition of the bark changed during bark development, and these terpenoid proportion changed with increasing bark thickness. The ratios of terpinen-4-ol, bornyl acetate, and beta-bisabolene in trees A and B, and those of alpha-pinene, camphene, beta-pinene, 3-carene, limonene, 1,8-cineole, alpha-terpineol, and caryophyllene in tree B tended to increase with increasing bark thickness. Furthermore, the peak areas of 1,8-cineole and terpinen-4-ol in the bark of tree C increased as the phloem thickness increased. Additionally, the enantiomeric ratio of linalool varied with the inner bark development of tree C. Obtained results suggested that the terpenoids detected in this study provide a defensive function against wounding, especially in the phloem of L. umbellata var. membranacea.
This study systematically investigates the relationship between multiscale pore structure and liquid permeability in moso bamboo. Microscopy, mercury intrusion porosimetry, tracer experiments, and X-ray micro-computed tomography (X-mu CT) were employed to characterize pore features and size distributions, and to elucidate internal transport pathways and mechanisms. Liquid permeation is strongly governed by pore structure: longitudinal transport occurs mainly through vessel lumens, parenchyma cells, and fiber cells, with vessels serving as the most efficient channels, whereas transverse transport through pits and intercellular spaces is comparatively limited. Three-dimensional pore models reconstructed from X-mu CT data reveal differences in pore morphology and connectivity among different cell types, providing a structural basis for transport analysis at the pore scale and numerical simulation. This multiscale approach overcomes the limitations of conventional macroscopic permeability measurements, enhances understanding of liquid transport in bamboo, and supports bamboo functional modification and impregnation strategies.
For the southern pines, interlocking stone cells (sclereids) are a fascinating periderm feature comprising only a small fraction of the outer bark (rhytidome), yet contributing greatly to its density/hardness. This study addresses the long-overdue need to carry out wet chemical analyses on periderm and obliterated phloem layers, the former herein limited to the stone cells. Extractives distributions by polarity were similar between loblolly pine (Pinus taeda L.) periderm and wood samples; the total extractives content of the obliterated phloem was threefold higher. The claim that stone cells are highly lignified held true, with lignin contents that were 20 % higher than those for the wood.
