Wood Science and Technology最新文献

Lignin is one of the most complex biopolymers and is characterized by combination of monomers to form a variety of inter-monomer linkages, which successively build up the racemic polymer. The prevailing theory of lignin formation suggests that monomers are enzymatically oxidized into resonance-stabilized radicals that subsequently couple through radical–radical reactions to generate intermediates that are then stabilized via post-coupling reactions. However, this standard model for lignin formation is challenged by certain lignin structures that cannot be easily explained by this theory. One such structure characterized by a side chain carbon (α or β-position) linked to an aromatic C6 is the focal point of this minireview. The evidence supporting the presence of this structure in softwood lignin is scrutinized, leading to the conclusion that this type of structure is most likely formed during the lignification process. Possible mechanisms for its formation are discussed.

Alkali lignin (AL), as a bio-based industrial byproduct, has certain potential in improving the photostability of wood in outdoor applications based on its UV absorption feature. The present study developed aminated low molecular weight depolymerized AL for wood impregnation, and evaluated the pre- and post-modification weathering resistance of the wood. The filling of aminated AL within the wood matrix was demonstrated using methods including scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and fluorescence microscopy. Compared with AL treated wood, modified poplar and Chinese fir showed a high weight gain rate increased by 251.8 and 320.9%, respectively, and a low loss resistance rate decreased by 39.9 and 32.5%, respectively. Free radicals exhibited a reduced generation during in situ irradiation. Changes in composition over the same period of weathering treatment were minimized, thereby delaying the structural and morphological alterations induced by weathering. Macroscopic photodegradation and morphological damage observed in the modified wood were substantially mitigated, with the integrity of the anatomical structure preserved. These findings substantiate the protective effect of aminated AL treatment on wood weathering behavior, which is beneficial for enhancing the stability of wood in outdoor applications.

Iron-loaded Japanese cedar (JC) charcoal adsorbents were synthesized under various conditions to investigate their ability to adsorb 3d-block metal ions. The metal ions (Mⁿ⁺) examined in this study were Cr³⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺. Ordinary JC charcoal adsorbents used as references were also prepared under the same synthetic conditions. The aqueous Mⁿ⁺ solutions were prepared using metal chlorides and deionized water, and the concentration of Mⁿ⁺ was set to 2.5 × 10^− 2 mmol/L or 2.5 mmol/L. Fe(NO₃)₃ was used to synthesize iron-loaded charcoal. The Fe³⁺ content in JC wood, which was the crude material for iron-loaded charcoal, was set to 3 or 7% w/w by adding an appropriate amount of aqueous Fe(NO₃)₃ solution. JC wood powder impregnated with Fe³⁺ was heated at 600 or 800 °C for 1.0 h under a N₂ gas flow. The charcoal adsorbents were analyzed using Raman spectroscopy and X-ray diffractometry. The adsorption abilities of the JC charcoal adsorbents for Mⁿ⁺ ions were assessed based on adsorption isotherms, which consisted of double logarithmic plots of the adsorbed Mⁿ⁺ concentrations on charcoal versus the dissolved Mⁿ⁺ concentrations in aqueous solution.

Interfacial interactions between constituent phases are critical determinants of mechanical and physical performance in polyurethane–wood composites (PU-WCs), especially when modified with bio-based components. Despite the growing interest in bio-based PU systems, a detailed understanding of interfacial interactions in PU-WCs remains limited. In this research, PU-WCs with various additions of bio-based polyol (BP) were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Additionally, PeakForce Quantitative Nanomechanical Property Mapping (PeakForce QNM) was conducted to investigate the nanomechanical properties of PU-WCs. Our findings revealed a strong adhesion between the phases of the unmodified composite. A significant reduction of interphase thickness from 441.5 to 94.3 nm was noticed after the addition of BP, suggesting a weakening of interfacial interactions and reduced compatibility between phases in the PU-WCs. The adhesion image revealed the existence of two separated phases with different adhesion forces, where the brighter domains may be assigned to relatively high-rigidity isocyanate-rich domains and darker ones to polyol-rich domains. The maximal adhesion force decreases from 2.8 nN for PU-WC0%/BP to less than 1 nN for PU-WC80%BP. These findings highlight the importance of molecular architecture and interfacial structure on PU-WC performance and provide interesting insights for the design of novel wood-based materials.

Microwave treatment has shown potential to improve the hygroscopic stability of wood via cross-scale interactions between chemical composition and pore structure. This study investigated the hygroscopic behavior of microwave-treated Cunninghamia lanceolata earlywood and latewood, revealing different responses driven by changes in chemical composition and pore structure synergy. The experimental results showed that microwave treatment reduced the equilibrium moisture content across a wide range of humidity, with the reduction in earlywood being pronounced than that in latewood. At the molecular level, modification of chemical composition, especially those resulting from reduced hemicellulose and hydroxyl accessibility, played a dominant role in limiting the moisture absorption capacity. At the cellular structural level, microwave-induced vapor pressure reshaped the micro-mesoporous network structure, including separation of rimmed pits and cell wall microcracks, further limiting the water retention capacity of wood. The high sensitivity of earlywood to microwave treatment stems from its inherent structural chemistry, which exacerbates chemical degradation and structural damage. These findings establish a coupling mechanism between structural and compositional changes, whereby chemical absorption site loss supersedes pore structure evolution in controlling hygroscopicity, providing key insights for optimizing microwave parameters to improve hygroscopic stability of wood.

To explore the high-value utilization potential of bamboo rhizomes—typically discarded as forest residues—and to enrich the raw material base for bamboo-based plastic alternatives, this study systematically characterizes the micro-morphological features of Phyllostachys sulphurea rhizome (Golden-bamboo rhizome, G-rhizome) as a representative species, providing an in-depth understanding of its anatomical architecture and structural heterogeneity. Light microscopy, scanning electron microscopy, and computer-vision analysis were combined to map vascular bundles, fibers, parenchyma cells, and vessel elements in situ, followed by quantitative measurements of their dimensions and volumetric fractions. The results revealed that the overall anatomical configuration of G-rhizome closely resembles that of Phyllostachys edulis culm (Moso-bamboo culm, M-culm). However, the G-rhizome contained a markedly higher proportion of fibrous tissue (up to 48.57%). The fibers and parenchyma cells were smaller in size, while the vessel distribution exhibited a consistent radial gradient with vessel diameters averaging 127.93 μm—slightly smaller than those in M-culm. Moreover, the fibers in G-rhizome showed short length and low aspect ratio. These anatomical traits indicate that while the rhizome may not match the culm in structural reinforcement performance, it holds strong promise for conversion into biodegradable composites such as disposable tableware, flexible packaging, transparent films, and 3D-printing feedstocks, thereby expanding the resource base for bamboo-for-plastic initiatives.

The exploration and high-value utilization of sustainable biomass materials have attracted substantial interest. In this study, ornamental bamboo biomass with varying growth forms influenced by different environmental conditions was investigated. The tissue anatomy and cell wall topochemistry of the bamboo species were analyzed via a series of advanced microscopic techniques. In addition, the crystal structures of the feedstocks and their variations attributed to bending effects were elucidated. After conventional mild acid pretreatment, the bioconversion performance of the bamboo materials was evaluated. Straight bamboo samples exhibited higher vascular bundle density, increased lignin content predominantly distributed in the middle lamella, and a greater proportion of crystalline cellulose located within the secondary wall of both fibers and parenchyma cells. These topochemical and supramolecular variations substantially influenced the pretreatment and bioconversion performance of the bamboo species. This study provides novel insights into the utilization and application of various bamboo processing materials for the development of value-added products.

The nitration reaction makes it possible to depolymerize the structures of condensed lignin to produce valuable chemical products. The physicochemical properties data of lignin nitro derivatives are necessary for their use. The nitrolignins were obtained on the basis of a slightly altered sample of dioxane lignin extracted from spruce wood. Water and ethanol solutions of nitric acid were used as nitrating agents. Changes in the elemental and functional composition, macromolecular, acid-base, redox, and electrophysical properties of lignin were determined by a complex of analytical methods. Characteristic changes in the conductive and dielectric properties of nitrolignins in the range of lower and medium frequencies of the electric field from 10^− 2 to 10³ Hz have been established. The interrelation of the functional nature and physicochemical properties of lignin was shown.

Most Japanese cedar heartwood is reddish in color, but some of the wood is blackened. This phenomenon is related to the high potassium concentration, weak alkalinity, and denaturation of norlignans. Owing to its dark color and high moisture content, blackened wood has a low timber price. In this study, binderless boards were produced from black heartwood, and the mechanical performance and water resistance were compared to those of normal (red) heartwood. The changes in the main wood components and extractives caused by heat and pressing were also analyzed. The results showed that the mechanical performance and water resistance of black heartwood boards were higher than those of red heartwood boards. The optimal production conditions were 220 °C for 20 min for red and black heartwood, or 240 °C for 10 min for black heartwood. Norlignan analysis revealed that more sequirin-C was lost during the hot- pressing of black heartwood. In the infrared spectra, a peak around 1717 cm^–1 appeared only after the black heartwood samples were hot-pressed. These results indicate that the hydroxy group–rich sequirin-C may have formed new ester bonds with the carboxyl group of hemicellulose during hot-pressing, thereby increasing the internal bonding strength.

Gnetum gnemon (Gnetales) is a woody gymnosperm exhibiting morphological characteristics similar to those of woody angiosperms. This study investigated the mechanism underlying negative gravitropism observed in the inclined stems of G. gnemon at two plantation sites on Java Island, Indonesia. The following results were obtained: On the upper side of the inclined stem of G. gnemon, (1) eccentric growth occurred in both the xylem and the phloem; (2) significant tensile growth stresses were generated on the surfaces of the xylem and the inner phloem; and (3) a small microfibril angle (MFA) along with high cellulose crystallinity were observed in both the xylem and the inner phloem. Furthermore, (4) G-fibers developed predominantly on the upper side of the inclined stem, especially in the inner phloem, while no G-fibers were detected in the xylem. From these results, it can be concluded that reaction wood with a small microfibril angle (MFA) and high cellulose crystallinity in the lignified secondary-wall of the xylem fiber, along with reaction phloem containing G-fiber, generate significant tensile growth stresses on the upper side of the inclined stem of G. gnemon. In other words, although G. gnemon is a gymnosperm, it exhibits negative gravitropism through a mechanism not typical of normal gymnosperms but rather similar to that observed in angiosperms.