Wood Science and Technology最新文献

Acetylation is a wood modification method that reduces the hygroscopicity of wood and increases its resistance to degradation by wood decaying fungi. Even though acetylated wood can have very high decay resistance, the wood material can be degraded and sometimes deacetylated by fungi. This study investigated the degradation and deacetylation of acetylated wood by Coniophora puteana and Rhodonia placenta to better understand the relationship between degradation and deacetylation in two different brown rot fungi. Wood samples were exposed to the fungi in a stacked-sample decay test, followed by acetyl content measurements and FTIR spectroscopy to investigate chemical changes in the samples. The results showed that both fungi could degrade acetylated wood to high mass loss despite a strong reduction in moisture content, but only R. placenta was found to cause preferential deacetylation. The deacetylation was slight and only observed in the early stages of decay in highly acetylated wood. Otherwise, acetyl groups were lost from the samples at the rate of mass loss. FTIR spectroscopy confirmed the loss of acetyl groups and revealed some chemical differences between unacetylated and acetylated wood. The spectral data indicated the loss of acetyl groups from lignin, which suggests that the loss of acetyl groups is not only due to the degradation of acetylated carbohydrates. The degradation of acetylated wood required further investigation, but it is clear that extensive deacetylation is not a requirement for brown rot degradation.

Four new peltogynoid monomers (3, 7, 10, 11) and a new peltogynoid dimer (9) were isolated from the heartwood of Peltogyne mexiacana, along with six known compounds (1, 2, 4, 5, 6, 8). Among the known compounds, the absolute configurations of two flavanones (5, 6) were determined. The structures of the isolated compounds were determined using NMR and MALDI-TOF MS analysis. The discoloration of the methanol solutions of the isolated peltogynoids and flavanones was examined by exposing them to room light in the air. The methanol solutions of (+)-peltogynol (1) and (+)-mopanol (4) discolored to reddish and bluish purple, respectively. After discoloration, the b* values of these compounds decreased significantly from 12.1 to 19.1 to -0.7 and − 1.8, respectively. These precursors of pigment compounds 1 and 4 have a catechol moiety in the B ring, and a hetero-six-membered ring (D ring) connecting the B and C ring of flavan-3,4-diol via an oxyethylene bridge, which is similar to the structure of leucoanthocyanidin. These results led to the hypothesis that the metabolized pigment compounds have anthocyanidin-like structures with peltogyne skeleton.

Wood is an important construction material, but a significant problem hindering its widespread use is susceptibility to biodeterioration and biodegradation. To protect wood against degradation, a surface coating can be used, and it is important to be able to predict the ability of the coating to prevent fungal growth. The currently available standard method to determine the antifungal efficiency of a coating has two weaknesses, viz. no evaluation of the moisture content in the wood material, and no possibility to study antifungal effect of the coating towards an individual fungus. A new quantitative method of determining the antifungal efficiency of coatings is therefore proposed, where a coating is applied to wood and exposed to an individual fungus in a Petri dish. Six commercial water-based coatings containing synthetic biocides were studied on filter paper (EN 15457) and with the new test method on wood blocks. The results show the importance of studying the antifungal efficiency of a coating using individual fungi instead of a mixture of fungi, since individual fungi interact differently with a given biocide in the coating. The moisture content of the wood substrate during the test was affected by how the fungus was established on the coating. This new test approach shows promise in screening the antifungal efficiency of wood coatings containing preservative substances applied to wood material surfaces.

Products made with veneers such as Laminated Veneer Lumber can reach higher properties than solid wood because the defects such as knots (but not only) are distributed among the various layers. Visual sorting, even using automatic grading, is only partially efficient for evaluating mechanical properties, which mainly depends on the fiber orientation and the density both at local scale. An experimental protocol has been established to correlate the nondestructive (fiber orientation and density) estimation and the destructive (tensile test) measurement of beech veneer wood. The aim is to understand the impact of the small imperfections on clear wood in fiber orientation on the mechanical properties. In the present study, wood veneer is assumed to be a transverse isotropic material due to the predominant wood fiber direction in the growth direction of the tree. Experimental measurements of modulus of elasticity are based on Digital Image Correlation (DIC) and virtual extensometer. The Young modulus model is based on a composite material model that considers fiber orientation and density. The Young modulus model is used to determine longitudinal, transverse, and shear moduli, for specimens with angles ranging from 0 to 45°. Mechanical properties are obtained by mathematical minimization between experimental and model data. The coefficient of determination obtained was 0.97. The measure of the fiber angle with a resolution of 1 × 1 mm² and the tensile test with the DIC, both local, significantly improve Young modulus measurement compared to previous studies’ assessment accuracy and allow for a better understanding of the wood behavior.

Chestnut Red Stain (CRS) is a heartwood discoloration that widely affects Castanea sativa Mill. productive coppice stands in the northeast of Spain. At the early stages of infection, the structural properties of the wood are not affected, but still its economic value drops up to 70% due to the rejection of this wood. This disease is caused by the fungus Fistulina hepatica (Schaeff.) With. and causes uncertainty to forest managers since the fungal infection is virtually impossible to detect before felling. The objective of this work was to develop an efficient detection method to evaluate the presence of F. hepatica in early stages of productive periods. A total of 72 chestnuts were analyzed through molecular methods to determine the presence of F. hepatica and with an IML resistance drill to characterize their wood. Thirteen wood quality indices were calculated and their correlation with the presence of the pathogen was evaluated using linear mixed models. We found clear differences between healthy and infected trees in four indices. A new specific index (Chestnut Red Stain Danger index) was designed to estimate the probability of infection by F. hepatica. The results support the hypothesis that the early presence of F. hepatica is detectable through inexpensive and fast mechanical methods early in a rotation. The results of this work will help forest managers evaluate the incidence of CRS, as well as it establishes a novel methodology for further development of resistance drilling techniques for heartwood rot detection.

Chemically and biologically degraded Scots pine wood was prepared as a model material for the research on new conservation agents for waterlogged archeological wood. In this study, the model wood was characterized using a 2D¹H–¹³C solution-state NMR technique without derivatization, isolation, or extraction to assess the effect of applied degradation processes on its chemical composition and structure. The results clearly show how the two artificially degraded model wood types are chemically different. Biological decay by the brown-rot fungus Coniophora puteana caused degradation of wood polysaccharides, with heavy depletion in arabinan, mannan, and galactan, along with an increase in the cellulose's reducing ends (i.e., lowering the degree of polymerization) and partial deacetylation of mannan. The fungus cleaved roughly one-fifth of the β-aryl ethers in lignin, leading to a broadening effect on the lignin aromatic unit contours; other lignin sidechains were left untouched. Chemical degradation by NaOH hydrolysis resulted in a depletion in mannan, galactan, and glucan, as well as efficient deacetylation of mannan. It also decreased lignin content, causing changes in its structure; minor β-aryl ether cleavage along with substantial phenylcoumaran cleavage were evident. Detailed knowledge about the chemical composition and structure of artificially degraded model pine wood obtained in this research is necessary to understand the reactivity of these wood types with chemicals used for their conservation. This research will help explain the differences in the stabilization effectiveness observed between these wood types treated during conservation and understand the stabilization mechanisms, thus contributing to developing new, more effective conservation agents for wooden artifacts of Cultural Heritage.

Cellulose nanofibers (CNFs) were isolated and prepared from six different plant sources (Nordic pine, poplar, cotton, flax, bamboo, and pineapple leaf fibers) through a carboxymethylation-homogenization treatment. The surface morphologies, size distributions, and chemical structures of the CNFs and their microfibers were investigated in detail. Atomic force microscopy (AFM) analysis showed that all kinds of CNFs had uniform diameters of less than 10 nm. However, the length and aspect ratio of CNFs exhibited significant differences due to the differences of anatomical characteristics from pulp species. Among these six nanofibers, the pineapple leaf-based nanofibers had the highest length of ca. 2.21 μm and aspect ratio of ca. 1263. Meanwhile, the resulting pineapple leaf-based nanocellulose film possessed the strongest tensile strength (229.0 ± 9.8 MPa) and toughness (33.9 ± 2.9 MJ/m³). Interestingly, the aspect ratio of cotton nanofibers was only 556, lower than that of bamboo, Nordic pine, and flax nanofibers, but the tensile strength (210.6 ± 4.8 MPa) and toughness (22.4 ± 0.6 MJ/m³) of cotton-based nanocellulose film were second only to the pineapple leaf-based nanocellulose film. The critical reason is that the cotton-based nanocellulose exhibited the highest crystallinity index (76.6%), superior to the other source-based nanocellulose. These results suggested that the high aspect ratio or high crystallinity are responsible for the excellent mechanical strengths of the nanocellulose film. This work sheds light on the preparation and selection of highly spindly or crystalline nonwood nanofibrils, suggesting that the pineapple leaf or cotton nanofibers have great potential as strength additives for nanocomposites.

Condensed tannins (CTs) characterized by a low degree of polymerization (DP) are recognized to have substantial value for applications across diverse industrial sectors, including food production, pharmaceuticals, and wood adhesive manufacturing. To acquire CTs with a low DP, the depolymerization of bayberry tannins (BTs) through a novel approach utilizing UV light-driven photocatalytic degradation, facilitated by the ultrasonic dispersion of TiO₂ nanoparticles was investigated. Under the optimal degradation conditions (a tannin concentration of 6%, a TiO₂ nanoparticles loading amount of 0.20%, and a degradation time of 4 h), the study delineated a discernible linear relationship correlating both the degradation time with the formaldehyde reactivity of the photocatalytic degradation products, and the formaldehyde reactivity with the mean degree of polymerization (mDP) of these photocatalytic degradation products. With the establishment of these correlative relationships, it is feasible to systematically control the degradation process of BTs. The photocatalytic degradation process adhered to the following mechanism: The degradation process of BTs is initiated by the cleavage of the C4-C8 bond which, at the incipient stage of degradation, results in the elimination of one gallocatechin gallate unit and one gallocatechin unit, or alternatively, the removal of a gallocatechin dimer. During the advanced stages of degradation, the opening of the C ring gives rise to different derivatives. Upon establishing optimal degradation parameters, it was observed that the primary constituents of the photocatalytic degradation products were dimers. The utilization of photocatalytic degradation exhibited an ability to break down condensed tannins in a manner that is both controllable and in an environmentally friendly way.

The exploitation of low-cost, non-fossil membrane materials with flourishing pore structure is essential to complete an organic dye wastewater treatment in Fenton-like catalytic technology. The accessible and scalable veneer functionalized Fenton-like catalysis has been manufactured to decolorize the effluents by a hydrogen peroxide-Mn-based oxides system. The nanocatalyst of Mn-based oxides has been loaded on the veneer surface by the hydrothermal in-situ growth, which could accomplish the coupling of Fenton-like catalyst and membrane technology. Fir and poplar veneers with unique three-dimensional porous structure have been investigated in detail to manifest the respective performance of decolorization during the dye wastewater treatment. This work not only has invented a promising membrane material coupling with Fenton-like catalysis to dispose dye wastewater, but also provides a reference in high-performance membrane design of biomimetic membrane.

Turning lignin from black liquor waste into value-added bioactive agents is one of the possible routes for improving the sustainability and profitability of lignocellulosic industry. However, due to chemical and structural variability of lignin, it is necessary to isolate specific lignin fractions from black liquor with the purpose to achieve samples with unique chemical and structural characteristics and therefore, specific biological activities. In this study, poplar lignin fractions isolated from Kraft black liquor by sequential acid precipitation at pH´s 7.5, 5 and 2.5 (denoted as P-7.5, P-5 and P-2.5) were characterized according to their physicochemical, antioxidant and antibacterial properties. In general, lignin fractions displayed a wide elimination of lateral chains (aryl-β ether and C–C) and, therefore a high phenolic content and low molecular weight, as the pH sequential precipitation was decreased from 7.5 to 2.5. Moreover, thermal analysis revealed that the P-7.5 lignin fraction showed higher thermal stability than P-2.5 and P-5. In terms of antioxidant activity, the P-7.5 lignin fraction, with a higher S/G ratio and a less oxidized structure compared to P-5 and P-2.5, exhibited higher antioxidant activity. In addition, lower antibacterial effect was observed for all lignin fractions against Escherichia coli compared to that obtained against Staphylococcus aureus. Among them, the P-2.5 and P-5 fractions, with higher phenolic content and lower molecular weight values than P-7.5, showed a greater antibacterial effect against S. aureus.