Wood Science and Technology最新文献

Chinese fir (Cunninghamia lanceolata) wood has been widely used in structural applications owing to its excellent machinability and rapid growth. A comprehensive understanding of its mechanical behavior, particularly under compression loading, is critical for ensuring the reliability and safety of structural components. This study explored the failure behavior of Chinese fir wood under axial, radial, and tangential compression using micro-computed tomography (micro-CT) and digital volume correlation (DVC) techniques. The results revealed that Chinese fir wood exhibited high compressive stiffness under axial compression, with displacement and strain localized around inherent defects. Under radial compression, significant strain concentration was observed at earlywood tracheid lumens and growth ring interfaces, which acted as primary sites for strain localization, initiating localized failure and subsequent deformation propagation. In tangential compression, the wood demonstrated moderate compressive strength with relatively uniform deformation, although stress concentration persisted in weaker regions, particularly within earlywood tracheids. These earlywood tracheids, characterized by thinner walls and larger lumens, played a pivotal role in stress concentration and failure propagation, accelerating localized damage. This study underscores the anisotropic mechanical behavior of Chinese fir wood under compression in three directions and elucidates the associated damage evolution mechanisms, providing a theoretical foundation for evaluating its mechanical properties and guiding structural optimization.

Two new types of anthocyanidins, mopanidin (1) and peltogynidin (2) were isolated from the heartwood of Peltogyne mexicana for the first time. The structures of the isolated compounds were determined using NMR and MALDI-TOF MS analysis. These pigment compounds had flavylium moiety and oxymethylene bridge between B and C ring (D ring), and resorcinol moiety as B ring. The result of the monitoring of the oxidation of pigment precursors, it was clarified that 1 and 2 were generated from (+)-mopanol and (+)-peltogynol, respectively. The compounds were considered to be produced by light and oxygen in a different way from common anthocyanidins. Compared to cyanidin, which has similar structure except D ring, 1 and 2 showed an additional absorption around 560–570 nm to show more blueish purple. In addition, they showed more stability than cyanidin in neutral and acidic condition. Considering the result of in silico calculation of their dihedral angles consisting of the AC and B rings, 1 (θ = 174.4º) and 2 (θ = 172.0º) had a nearly planar structure, while cyanidin had a twisted structure (θ = 154.2º). It was suggested that the bulkiness around C-2 due to the nearly planar structure in 1 and 2 contributed to their relatively color stabilities in neutral condition. These findings provide insight into the structural features influencing pigment stability and color change mechanism of P. mexicana.

Archaeological wood requires effective conservation to prevent further degradation, and traditional modifications such as polyethylene glycol (PEG) have limitations, including hygroscopicity and chemical degradation over time. To explore alternative modification, this study was conducted to investigate the suitability of humins, crosslinked with different concentrations of succinic acid (SA), to protect archaeological elm wood from the Agapia Monastery against water and to determine the modification mechanism. Key parameters such as dimensional stability, moisture sorption isotherms, and determination of accessible hydroxy groups as a function of humination modification were analyzed using dynamic vapor sorption (DVS). The modification mechanism was studied by microstructural and chemical properties evaluation by Confocal-Raman spectroscopy and scanning electron microscopy (SEM). Results indicated that humins, particularly crosslinked with SA, significantly improved the water-related properties of wood and its dimensional stability. The humination also reduced the accessibility of the hydroxy group, thus decreasing the equilibrium moisture content (EMC) of huminated elm at relative humidities (RHs) ranging from 0 to 95%. While SEM images revealed structural changes in the modified wood, Confocal-Raman spectroscopy confirmed the successful allocation of humins into the cell walls. This study demonstrates that humins are promising materials for archaeological wood conservation, providing improvements in both chemical and physical properties.

Given the declining demand for newsprint and the rising demand for packaging materials, new applications for high-yield pulps (HYPs), such as sustainable packaging, are being developed. While the traditional use of HYPs as a major component in paperboard is growing alongside this demand, their use in other packaging types with different property demands requires quality modifications or improvements to enhance mechanical strength and/or barrier properties. The research presented here explores the role of lignin and lignin-rich fine content, combined with hot-press technology, in improving the paper produced with chemithermomechanical pulp (CTMP). Critical properties for some packaging materials, as tensile strength (dry and wet) and air permeability were evaluated. Results indicate that moderate delignification (15%) or increased fines content together with hot-pressing improves the evaluated properties. The highest dry tensile strength was achieved through soft delignification, tripling the resistance (from 27 to 83 kN m/kg). Maximum wet strength (28 kN m/kg) was obtained with 35% fines content and 260 °C hot-pressing, which also resulted in the densest sheets. Air permeability was significantly reduced, either through partial delignification or by increasing the fines content, resulting in values decreasing from approximately 2000–20 mL/min. This approach aims to develop more sustainable packaging materials without relying on wet strength additives typically derived from fossil raw materials.

Combining metal with transparent wood to give it good electrical conductivity is of great practical significance for the functional improvement of wood and the expansion of application areas. In this paper, transparent wood was prepared by delignification treatment and impregnation of epoxy resin with balsa wood as the substrate, and nano-Cu film/transparent wood composites were prepared by magnetron sputtering. The microstructure, surface morphology, hydrophobicity and electrical conductivity of the composites were characterized and tested. The results show that: when the sputtering time reaches 30 min, the surface of transparent wood is almost completely covered by the nano-Cu film, and a “sheet-like” dense nano-Cu film is formed on the surface of the sample, which realizes the metallization of the surface of the transparent wood; at 2θ equal to the vicinity of 43.3°, 50.4° and 74.1°, the metallic copper Cu (111), Cu(200) and Cu(220) diffraction peaks appeared; the Cu element content on the surface of transparent wood reached 91.85%; the parallel to grain resistance is 1.24 Ω/sq and the across grain resistance is 1.62 Ω/sq, which can be seen that the composite of metallic material and transparent wood using magnetron sputtering, a purely physical method, successfully prepares the nano-Cu film/transparent wood with the surface square with the resistance value lower than 2 Ω/sq, which also has opened up more possibilities for applications in modern electronics, architectural and decorative materials, and other related fields.

Grey alder Alnus incana (L.) Moensch bark represents a prospective raw material for acquiring a broad range of high-value green chemicals with various biological activities. Bark, rich in valuable extractives, is considered an important resource for sustainable development because of its abundance, renewability, and availability. Herein, we investigated the longitudinal variability of A. incana bark chemical composition and bark extractives yield for their potential utilization/valorisation. A. incana bark extractives were obtained by Soxhlet extraction using four solvents of different polarities: ethanol, ethyl acetate, petroleum ether, and water, while the bark samples were collected from three trunk heights. Extractive contents (EC) and total phenolic content (TPC) were determined, as well as their antioxidative (AO), antimicrobial, and cytotoxic activity were examined. The results showed that the A. incana bark contains an elevated amount of extractives compared to the other deciduous tree species with the highest content found for water and ethanol extractives. The extractives exhibited high antioxidative activity and antibacterial effects on eight Gram-positive and seven Gram-negative bacterial stains. Furthermore, the A. incana bark extractives showed antiproliferative activity towards two human breast adenocarcinoma cell lines MCF-7 and MDA-MB-231. The ethyl acetate extract showed the best activity on the inhibition of the growth of the MDA-MB-231 cell line (IC50 value 30.9 µg/ml). In contrast, the ethyl acetate extractive showed the best cytotoxic effect on the MCF-7 cell line (IC50 value 15.7 µg/ml).

The permeability of wood materials significantly affects wood modification, drying and further processing of wood-based building materials, and there is a need for a better understanding and evaluation of the permeability of wood materials. This paper presents a novel method for estimating the macroscopic permeability in wood by combining mercury intrusion porosimetry (MIP) data with the fractal theory. The characterization of wood’s structural parameters through MIP provides essential geometric data for the subsequent modelling process. A computational model for permeability was established based on principles of fractal geometry and seepage flow theory. This model aimed to elucidate the relationship between the structural characteristics of wood and its permeability behaviour. By deriving an explicit expression for permeability, the model incorporated critical structural parameters, e.g., minimum and maximum pore size, pore size distribution, porosity, fractal dimension, and the fractal dimension associated with tortuosity. The permeability of the three wood species studied, i.e., Scots pine, white birch, and oak, was 28.6, 13.6 and 1.4 mD, respectively. To validate the model, the calculated permeability values were compared with experimentally measured data, showing a strong correlation and confirming that the model accurately reflects the permeability behaviour of wood based on its structural characteristics. Notably, the model demonstrated the effectiveness of utilizing MIP data in conjunction with fractal theory, thus, the computational efficiency of this method significantly surpassed that of traditional numerical simulations, which allowed a better understanding of the interplay between structure and permeability in wood.

Ancient archeological wooden artifacts hold important stories from our history that can only be retold through wood conservation. Understanding the detailed mechanisms of how to stabilize these fragile artifacts dimensionally is necessary to effectively preserve them for the next generations. In this study, highly effective organosilicons are used to treat and infiltrate model degraded wood. We used wood dissolution techniques, in conjunction with two-dimensional nuclear magnetic resonance spectroscopy, to characterize the changes occurring to native wood cell wall polymers before and after organosilicon treatments. Methyltrimethoxysilane was shown to be the mildest organosilicon towards wood polymer depolymerization in the model woods, while the alkoxysilane with a mercaptopropyl group resulted in more dramatic cell wall depolymerization, removing lignin linkages and polysaccharides. The siloxane treatment did depolymerize the model woods as well, giving more intermediate cell wall depolymerization and leading to reduction of the α-carbonyl in G-2ʹ guaiacyl units in lignin. We hypothesize that the organosilicon treatments can effectively infiltrate cell wall matrices, partially depolymerize wood cell wall polymers, and meld the truncated wood polymers together to stabilize cell wall dimensions.

To release viscoelastically locked-in residual growth stress in wood rapidly, wood is treated by using boiling water. This process is called hygrothermal recovery (HTR). In this study, the mechanism of longitudinal HTR in Cryptomeria japonica (sugi) and Chamaecyparis obtusa (hinoki) treated at 120 °C was investigated. This study used juvenile and mature compression wood (CW) and normal wood (NW) and focused on the correlations of the HTR strain with the microfibril angle (MFA) and area ratio of lignified S2 (S2L) layer. The results revealed the following: In mature CW (M-CW) and juvenile CW (J-CW), both MFA and S2L area increased, and at the same time, large expansive HTR strain was observed. In M-CW, longitudinal HTR strain showed significant correlations with MFA and S2L layer. HTR strains ​​were more variable in J-CW than in M-CW. In mature NW (M-NW) and juvenile NW (J-NW), HTR strains were smaller than those of CW, and correlations between MFA and HTR strains were low. Based on these results, the following hypothesis is proposed: During the cell wall maturation, increased lignin and (1→4)-β-galactan concentrations in the S2L layer generate a large compressive growth stress along the fiber axis in CW, part of which remains as viscoelastically locked-in compressive stress. Hygrothermal treatment induces the softening of lignin and the water swelling of (1→4)-β-galactan in the matrix of S2L layer, which leads to a large expansion of the S2L layer, i.e., the release of the viscoelastically locked-in growth stress. Finally, the large MFA of the S2 layer and the large expansion of the matrix of the S2L layer generate a large expansive HTR strain in the longitudinal direction of the CW.

Wood-based electrothermal composites (WBECs) are increasingly employed in household building materials. However, their practical effectiveness can be significantly impacted by cooling and heating cycles and high-temperature-and-humidity environments. Therefore, we investigated the effects of electrothermal and hygrothermal aging on colorimetric parameters, resistance variations, and electrothermal properties. The results indicated that the surface color of WBECs gradually shifted toward red and yellow with increasing electrothermal power density and the application of hygrothermal treatment. Similarly, the brightness and gloss value decreased, with the maximum gloss loss rate reaching 45.42%. The resistance of the WBECs increased during the aging process from 76.1 Ω in the control sample (in CS) to 147.27 Ω in the sample subjected to hygrothermal aging after electrothermal treatment at 2000 W/m² for 700 h (in EH2-3), corresponding to an increase rate of 93.52%. Owing to the aging of the internal carbon fiber conductive network and damage to the adhesive interface, the WBECs became more sensitive to temperature and hygroscopicity. Furthermore, the maximum surface temperature and electric-to-radiant power transfer efficiency of the WBECs considerably decreased from the control sample re-loading 1000 W/m² (CS-1) to EH2-3, while the temperature nonuniformity increased from 2.71 ℃ in CS-1 to 17.90 ℃ in EH2-3. High-temperature carbonization further demonstrated that the influence of hygrothermal aging on the structure and properties of the WBECs was greater than that of electrothermal aging. These results provide technical support for the stable and safe heating of WBECs in complex application environments.