Adhesion of fibers within a spun tow, including carbon fibers and precursors, is undesirable as it may interrupt the manufacturing process and entail inferior fiber properties. In this work, softwood kraft lignin was used together with a dissolving pulp to spin carbon fiber precursors. Lignin–cellulose precursors have previously been found to be prone to fiber fusion, both post-spinning and during carbon fiber conversion. In this study, the efficiency of applying different kinds of spin finishes, with respect to rendering separable precursors and carbon fibers, has been investigated. It was found that applying a cationic surfactant, and to a similar extent a nonionic surfactant, resulted in well separated lignin–cellulose precursor tows. Furthermore, the fiber separability after carbon fiber conversion was evaluated, and notably, precursors treated with a silicone-based spin finish generated the most well-separated carbon fibers. The underlying mechanism of fiber fusion post-spinning and converted carbon fibers is discussed.

Vanillin is an antifungal and environmentally friendly compound. In this study, vanillin and silica microcapsules (VSM) were microencapsulated using the sol-gel method and then impregnated into wood. Scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA) and transmission electron microscopy (TEM) were used to characterize the morphological structure and distribution of VSM in wood. Fourier transform infrared spectroscopy (FTIR) was used to study the intermolecular interactions between VSM and wood. The antifungal performance of the VSM-treated wood was evaluated. The study revealed that VSM had good sustained-release performance and decay resistance. Mass losses of VSM-treated wood after leaching and exposure to Trametes versicolor (L.) Quel. and Gloephyllum trabeum (Pers.) Murrill decreased from mass losses of 20.8 % and 15.9 % of the control group to 9.2 % and 6.4 %, respectively. VSM treatment disrupted the mycelium of T. versicolor and G. trabeum, inhibited their respiratory metabolism, and the ligninase-laccase enzyme activity of T. versicolor. Meanwhile, MOR and MOE of VSM-treated wood were 96.7 MPa and 12.3 GPa which were 28.8 % and 11.5 % higher than the control group, respectively.

Variation in anatomical features of the culm wall namely the shape and size distributions of vascular bundles between different genera and species of bamboo is not well understood due to the cumbersome task of manual measurements. Using machine learning methodology, this work presents a universal vascular bundle detection model for rapid, reliable, and automatic characterization of vascular bundles in culm cross sections of 213 species across 23 genera of Chinese bamboos. The number of vascular bundles and the fiber sheath area have positive linear correlations with the outer circumference and the wall thickness, respectively. The distribution density of vascular bundles has a decay exponential correlation with the outer circumference and the wall thickness. The average fiber volume fraction was 35.2 % ± 7 % with relatively small variation between species. Bamboo species could be grouped into three categories based the endodermis to epidermis distribution pattern of radial and tangential length of vascular bundles, two categories of radial-to-tangential ratio and four categories of fiber sheath area distribution pattern. Implications on bamboo classification, structural and pulp/paper applications were discussed. The findings from this study provide groundwork for the establishment of a unified, authoritative and objective bamboo classification system based on the vascular tissue morphology.

Wood is a biosourced material with unique aesthetic features due to its anatomy and chemical composition. White oak wood surface color can be modified with the use of iron salts, which react with wood phenolic extractives, present as free molecules in wood porous structure. The impact of modifying wood surface color with iron salts on the final appearance of wood, including its color, grain contrast and surface roughness, was evaluated in this study. Results showed that following the application of iron (III) sulphate aqueous solutions on white oak wood surface, its roughness increased, which is due to grain raising after wetting of wood surface. The color modification of wood surface with iron (III) sulphate aqueous solutions was compared with a non-reactive water based blue stain. The contrast associated to wood grain that was expressed by the standard deviation of luminance values in wood images, also increased after application of the iron (III) sulphate aqueous solution on white oak wood surface. The comparison of contrast changes showed that wood samples stained with iron (III) sulphate on their curved surface had the highest increase in grain contrast compared to iron-stained wood showing the straight grain and to wood surfaces colored by a non-reactive water-based stain for both curved and straight grains.

To address the low accuracy of non-destructive detection of moisture content (MC) of logs (especially in small diameters) by ground penetrating radar (GPR) signals, the MC of 10–15 cm diameter spruce, Manchurian ash, and white birch logs were predicted using the time-frequency parameters of the GPR signals and a back-propagation neural network (BPNN) model. B-scan signals were obtained using tree radar on the barks of discs selected from fresh green logs. Then, 31 time-frequency parameters from the B-scan signals were optimised using the least absolute shrinkage and selection operator (Lasso) and principal component analysis (PCA). Finally, the log MCs of the single and hybrid models was predicted using the BPNN. The accuracy of the least absolute shrinkage and selection operator and back-propagation neural network (Lasso-BP) were higher than those of the principal component analysis and back-propagation neural network (PCA-BP), and the BPNN. The individual species and hybrid models both have good predictive capability; when the log MC is below 20%, the maximum residual errors are relatively small, almost within 6% and 10%, respectively. These models significantly improve the accuracy of non-destructive detection of log MC and are beneficial for efficient wood processing.

The high polymer and low wood content of current transparent wood has limitation in the mechanical strength and hence obstruct green sustainable transition of the building industry. In this study, a novel method for manufacturing transparent wood was reported by minimizing the usage of polyethylene glycol using partial impregnation followed by a densification approach. The delignified wood was firstly partially impregnated by polyethylene glycol, and subsequently compressed to eliminate pores for the compressed transparent wood, providing the strong hydrogen bonds and dense structures for transparent wood. The wood content of the novel compressed transparent wood was dramatically increased to 64%, compared with the uncompressed transparent wood of 25%. Additionally, the obtained compressed transparent wood demonstrated satisfactory optical transmittance, suitable thermal energy storage, and superior mechanical strengths owing to the formation of densely packed microstructures. This novel, sustainable, and low-cost transparent wood was easy to be manufactured while having increased mechanical and energy-saving characteristics compared to those available in the existing market.

Hygrothermal recovery (HTR) is an irreversible dimensional change that occurs when green wood is heated under wet conditions. Reaction wood presents a substantial dimensional change owing to HTR. In this study, the HTR of reaction wood was examined to understand the mechanisms of HTR. This study aimed to elucidate the HTR of tension wood, and particularly its temperature dependency. Two types of analyses were applied to the data measured, namely the two-phase exponential model and the time-temperature superposition analysis. The two-phase model was well fitted to the data and showed that the evolution of HTR could be divided into initial recovery and subsequent continuum contraction. The intensity of the initial recovery increased with increasing temperature. Continuum contraction was not well characterized in this study. Time–temperature superposition analysis provided an apparent activation energy of 326 kJ/mol, which suggests that HTR is a lignin-related phenomenon. A simulation based on the analysis also simulated HTR behavior at ambient temperature in a standing tree.

Hygrothermal treatment is an effective method for improving the dimensional stability of bamboo. In this study, changes in the physicochemical properties of Neosinocalamus affinis after hygrothermal treatment were comprehensively investigated: the hemicellulose content decreased, C=O in the acetyl group and the hydroxyl content decreased and xylan was partially degraded. The dimensional stability of N. affinis gradually increased with temperature, and optimal values were obtained at 220 °C, as indicated by a 16.5% decrease in anti-swelling efficiency and a 93.7% increase in contact angle. Alterations in the macromolecular structure of lignin were also observed: the contents of β-O-4 linkages and p-coumarate decreased by 54.3% and 23.9%, respectively; β-5 linkages disappeared at 220 °C, as determined by heteronuclear single quantum correlation spectroscopy. However, the maximum values for crystallinity, nano indentation elastic modulus, and hardness were reached at 180 °C and were higher than those of the untreated samples by 8.6%, 19.9%, and 23.5%, respectively. With the combined application of physical mechanics and dimensional stability, hygrothermal treatment at 180 °C and 100% relative humidity was proved to exert the optimal effects on N. affinis. These results provide new and comprehensive insights into the mechanism allowing the modification of N. affinis by hygrothermal treatment.

The degradation of lignin can generate a variety of products with diverse applications. Lignin is abundant on earth; however, its high molecular weight and stable properties impede its development. Currently, acid-catalyzed degradation of lignin is a relatively common and promising catalytic method, particularly DES catalytic degradation, which is not only environmentally friendly but also features an excellent degradation effect. This report discusses the degradation mechanism and effect of the formic acid-choline chloride DES system for the degradation of alkaline lignin. According to fourier transform infrared spectroscopy (FTIR) and 1H-NMR spectroscopy, it is evident that the phenolic hydroxyl content of lignin increases after degradation, which indicates the cleavage of β-O-4′ ether bonds in the macromolecular structure. Gel permeation chromatography (GPC) was employed to determine the molecular weight of degraded lignin, and regenerated lignin with low molecular weight and low dispersibility was obtained. The minimum average molecular weight (M w ) was 2.3 × 103 g/mol. During the depolymerization process, it was also discovered that the repolymerization and degradation reactions formed a competitive relationship. The lignin oil contained primarily propanoic acid ethyl ester, acetic acid butyl ester, 2-methoxy-4-propyl phenol, 2-methoxy phenol, and apocynin, as determined by GC-MS.

The delignification of birch chips during kraft pulping was investigated, targeting both the impregnation and cooking steps. Wood chips were impregnated using white liquor, white liquor + NaCl, water or NaCl aqueous solution. Then, the chips were cooked in batch autoclaves applying the same constant composition cooking conditions for all samples. Pulp and two fractions of black liquor (bulk liquor and centrifuged liquor representing the liquor inside the wood chips and fibers) were collected after different pulping times and analyzed for lignin and carbohydrate content. The dissolved wood components were precipitated from selected samples and characterized with respect to composition, molecular weight distribution and structural motifs. Cooking chemicals in the impregnation liquors led to faster delignification and xylan removal during cooking. Higher contents of lignin and xylan were measured in the lumen than in the bulk. The concentration profiles also showed accumulation of dissolved material in the lumen over time, suggesting significant mass transport limitation from lumen to bulk. Further analysis revealed higher fragmentation/degradation of dissolved material with increasing pulping time and in the bulk when compared to the lumen liquor, as demonstrated by the lower molecular weights and the changes in chemical shifts in the NMR spectra.

To improve hydrophobicity and thermal stability, polydimethysiloxane (PDMS) emulsion and silica sol were used for depositing organic/inorganic hybrid coatings in wood. PDMS emulsion could provide the hydrophobic film to improve the hydrophobicity and dimensional stability owing to its low-surface-energy. Silica sol could significantly enhance the surface hardness and thermal stability due to its penetration in cell walls, indicating the pore-filling effect in wood. Moreover, in the hybrid system, silica incorporation in PDMS emulsion helped to form integrate coatings in wood via Si-O-Si cross-linked networks. The hydrophobicity, surface hardness and thermal stability of treated wood were related to the loadings of silica sol in the PDMS. Stiff silica could compensate the negative effect on thermal stability caused by PDMS, and synergistically improve the surface hydrophobicity and hardness of wood. This work opens a facile method to produce bio-based materials with satisfied hydrophobicity and thermal stability to be used in humid environments.

Branches remain in the forest environment as logging activity residue. Considering the large size of many Amazonian trees, their branches have considerable dimensions and can contribute to a sustainable wood alternative for various applications. Due to the formation of reaction wood in the branches, relevant macro and ultrastructural changes can occur in its characteristics in relation to the trunk wood. However, the woods of the branches are not technologically well known. Therefore, this work aimed to evaluate the wood quality of branches of Hymenaea courbaril L., comparing it with wood of trunks. The extractives and lignin contents, basic density, shrinkage, fiber biometry, microfibril angle and mechanical resistance to compression parallel to the fibers were analyzed. The branch wood had smaller fiber dimensions and a higher microfibril angle than the trunk wood. The basic density was similar between these materials. The linear and volumetric shrinkages were smaller in the branch wood than in the trunk, while the axial shrinkage was higher in the branch. The parallel compressive strength was also lower in the branch wood than in the trunk. The branch wood has properties suitable for products with higher added value such as furniture, decorative objects, floors and utensils in general.

Bamboo is susceptible to moisture-induced dimensional instability and cracking. Combining traditional methods with vascular bundle detection, the coordinates and fiber sheath area of each vascular bundle was determined accurately. Based on data fitting, the change in the shape of cross-section was quantified and analyzed based on parameters such as radius, radian, and arc length. The changes in the total area and the areas of different types of fiber sheath, as well as the changes in the arrangement of vascular bundles were studied. The results showed that when the moisture content was reduced from 64% to 0%, the radius of the cross section was increased by 21%, while the radian and arc length decreased by 22% and 6%, respectively. The fibers shrunk by 15%, which was greater than that of the other tissues except bamboo fibers (9%). The gradient distribution of the fiber volume fraction contributed to its asynchronous dry shrinkage. Significant radial and tangential displacements were found in vascular bundles. This work further elucidated the dry shrinkage mechanism of bamboo, and was of great significance for the quantitative analysis of changes in bamboo structure from a combination of micro and macro perspectives.

Poor dimensional stability restricts the commercial utilization of fast-growing wood. In this study, fast-growing poplar (Populus cathayana) was treated by removing hemicellulose with hydrothermal treatment and impregnating alkali lignin via full-cell process, synergistically, for enhanced dimensional stability. After modification, hydroxyl groups were reduced in hemicellulose removed wood (DHC), alkali lignin was observed to fill in the cell lumens of vessels and wood fibers in the impregnated wood (AL) and in the wood modified by hemicellulose removal with alkali lignin impregnation (DHCAL). Compared with untreated wood, the volumetric swelling ratio of DHC and AL decreased by 11 % and 21 % under relative humidity (RH) of 89 %, respectively. The volumetric swelling ratio of DHCAL decreased by over 50 %, indicating a positive synergistic effect. The combination of hemicellulose removal and alkali lignin impregnation treatment improved the dimensional stability of wood significantly by reconstructing wood chemical components with various levels of hygroscopicity. This work could meaningfully contribute to the efficient utilization of fast-growing wood and promote the added value of industrial alkali lignin.

Climate change from global warming raises the risk of wood decay. Knowing the inherent durability period of wood is crucial for long-term use. Hence, the natural durability of five important Korean wood species (Larix kaempferi, Pinus densiflora, Quercus rubra, Quercus variabilis, and Quercus serrata) was evaluated. In addition, the fungal diversity isolated from each wood stake was investigated to compare and analyze the differences in natural durability. The natural durability of the five wood species was determined to be highest in Larix kaempferi and Quercus serrata, followed by Quercus variabilis, Quercus rubra, and Pinus densiflora. Overall, 306 fungal isolates were collected, including 16 species of Ascomycota, 22 species of Basidiomycota, 15 species of Zygomycota, and eight unidentified species, which dominate different positions of the wood stake. Less Basidiomycota diversity was observed in the two wood species with high durability. In addition, the isolation of not only Basidiomycota but also Ascomycota and Zygomycota could affect wood deterioration and explain the association with wood durability. These findings are expected to be useful in improving the durability of useful wood in Korea in an era of climate change, where the risk of wood decay is increasing.

This study aimed to clarify the effect of the interactions between the swelling liquid and wood constituents on the creep behavior during drying. Creep tests were conducted during drying of four sample groups (untreated, acetylated, delignified, and hemicellulose-extracted samples) that were swollen using water, one organic liquid, or water-organic mixtures. The largest creep deformation was measured for the hemicellulose-extracted samples, followed by delignified, untreated, and acetylated samples. Apart from the acetylated samples, all treated samples tended to have large creep deformation in water-organic mixtures. For the acetylated samples, the creep deformation was small, except in case of acetone. These differences in the creep deformation behavior are mainly due to the differences in the glass-transition temperature of lignin as a result of the interaction between the wood constituents and the swelling liquid. The considerable increase in creep deformation due to hemicellulose-extraction suggests that hemicellulose, which interacts with lignin and cellulose, reduces the fluidity of the wood due to liquid desorption during creep measurements.

Plantation forests were originally established in South Africa to meet an increasing demand for solid wood products as there was a limited supply from native forests. The majority of the commercial softwood plantations were established with Mexican Pinus patula. Since growing conditions are known to impact tree growth, tree form, and wood quality of P. patula, sample plots were established over a cross-section of plantations in the Lowveld Escarpment and Highveld forestry regions of South Africa that covered an array of geologies and altitudes. Each sample plot was classified according to soil properties, rainfall, and temperature, and trees within the plots were measured for growth, form, and wood properties. Soil, growing days, and temperature were found to have little impact on tree form and wood properties. However, rainfall and specifically, spring rainfall, was found to have a highly significant impact on late wood formation, proportion of juvenile core, and wood density. In addition, tree height was found to be strongly correlated with maximum annual temperature.

The present study aimed to evaluate the effect of active alkali charge, in kraft cooking of Eucalyptus globulus wood, on the properties of the laboratory-produced tissue paper. Eucalyptus wood chips were cooked under similar conditions at four different active alkali (AA) levels of 16, 19, 21, and 23 % and DEDED sequence was used for subsequent ECF bleaching. Pulps were analyzed for their intrinsic viscosity, chemical composition, and fiber morphology, while the corresponding papers (20 g/m2) were examined for their strength properties, absorptivity, and softness. It was demonstrated that changes in the AA upon cooking, not only affected the chemical composition of the obtained pulps and their intrinsic viscosity, but also the fiber’s shape (e.g., curl and kink). These changes caused variations in the properties of laboratory-produced tissue papers. Thus, the increase in AA led to paper with lower tensile strength, but with better softness. Even though the increase of AA in cooking led to bulkier papers, their absorptivity was not significantly enhanced. This was explained, at least in part, by the lower water retention of the pulps obtained from cooking with higher AA.

The physical properties of wood are important parameters to qualify the material. However, as it is a heterogeneous material, moisture content and wood contractions may vary within the sample. Thus, the objective was to monitor the hydromechanical behavior of wood during drying using near infrared (NIR) spectroscopy and image analysis. Equidistant points were marked on the radial surface of a wooden board and NIR spectra were recorded at each marking during drying of the piece. After spectral acquisition in each drying step, images were obtained and the markings were referenced to monitor contractions during drying. Moisture content (MC) estimates via NIR spectra showed strong correlation with reference values (R2cv = 0.92, RMSEcv = 9.82 %). From the estimates it was possible to generate graphic images to visualize and quantify the spatial variation of MC and shrinkage during wood drying. In the initial stages of drying, the ends of the material showed high moisture in relation to the center of the sample. However, MC loss was 11 % greater at the ends of the wood board when compared to its interior while the shrinkage in external zones was 3 times greater than the internal part. The use of NIR technique associated with image analysis can be a promising tool for estimating moisture contents and contractions in wood.

To elucidate the mechanism of wood sandwich compression, the response of wood compressing yield stress to hygrothermal conditions was investigated in this study with respect to preheating temperature (30–210 °C) and moisture content (MC, 0–100 %). An associated functional model was developed to predict wood yield stress based on the measured MC and temperature in wood. A 1 % increase in wood MC or a 10 °C increase of temperature led to a decrease in wood yield stress exceeding 0.1 MPa. Significant variations in yield stress, exceeding 0.8 MPa, were observed between high MC layer(s) and the remaining layer(s) along the wood thickness when there was an MC variation over 5 %. Preheating the wood with by heating platens accelerated water/moisture migration in wood, resulting in relatively low yield stress in the wood interior areas where water/moisture had migrated. This study demonstrated that the comparatively low yield stress of some wood areas was responsible for sandwich compression. When mechanically compressed, only the wood layer(s) with lower yield stress was compressed, leading to sandwich compression, regardless of whether the mechanical force was applied tangentially or radially.