Wood Science and Technology最新文献

Formaldehyde released from particleboard poses a serious threat to indoor air quality, and there is an urgent need to develop efficient adsorbents to reduce its release. This study introduces micro-nano chitosan (multiscale chitosan cross-linked polymers, MNCs) as a novel adsorbent, synthesized via ionic gelation and systematically characterized in terms of their specific surface area (0.301 m²/g), average particle size (19.96 μm), spherical morphology, and surface functional groups. The formaldehyde emission from particleboard treated with 3% MNCs was found to be reduced to 70.7% of that of the control group on day 28 by the 1 m³ climate chamber experiment, which was a significant emission reduction effect. The adsorption kinetic analysis showed that the adsorption of formaldehyde by MNCs conformed to the pseudo-second-order adsorption kinetic model, and its chemical adsorption mechanism was attributed to the Schiff base reaction between the amino group on the chitosan ring and formaldehyde. In the C-history experiment, the C_m0 of control panel was measured to be 1.94 × 10⁵ mg/m³ and D_m to be 2.7 × 10⁻⁸ m²/s, whereas after treatment with 3% MNCs, the C_m0' was reduced to 0.29 × 10⁵ mg/m³, the D_m' was reduced to 4.31 × 10⁻¹⁰ m²/s and the partition coefficient K was enhanced from 243.9 to 855.5 in the original panels, indicating that the addition of MNCs significantly inhibited the diffusion of formaldehyde, enhanced the retention capacity of formaldehyde in the particleboards, and reduced the initial volatilizable formaldehyde reserves. This study provides theoretical basis and experimental support for the application of MNCs in the pollution control of wood-based panels, whose efficient emission reduction performance originates from the unique nanoporous structure and the active amino sites in chitosan molecules.

Agarwood is a highly valuable, fragrant resinous wood produced by Aquilaria trees in response to infection or injury. Agarwood obtained through the infestation by the insect Neurozerra conferta generally is in higher demand. It receives higher prices than artificially induced agarwood and is usually preferred by farmers and traders. Although different grades of insects infested and artificially induced wood are available in the market, no study exists that compared them to recognize the underlying reasons. Therefore, the present study, for the first time examines the difference between the insect-infested and artificially induced agarwood. Insect-infested and artificially induced resinous agarwood tissues were firstly segregated visually into grades and after that studied biochemically. The findings revealed significant differences in their phytochemical and polysaccharide constituent. GC-MS profiling with Principal Component Analysis (PCA), and Heatmap analysis not only validated the visual grading of agarwood but also the existence of key biochemical variations (mainly cellulose, and lignin) between the two types of wood. Furthermore, the findings indicate the possibility of repression of the defense mechanism in Aquilaria malaccensis trees by the insect N. conferta and thereby regulates the synthesis of other compounds which could be the possible reason that makes it better in its quality. Although the selective infestation of the A. malaccensis trees by the insect in contrast to blanket artificial induction creates limitations on the extent of commercial agarwood resin induction, yet the same selectivity helps in selecting suitable trees that can confer a clear qualitative advantage in agarwood resin development.

A three-dimensional level set-based image segmentation method is presented for a robust identification and accurate characterization of the different cell types defining complex wood micro-structures. The method can be applied to arbitrary wood species, and in this contribution is elaborated for oak. The evolution of the level set function and the corresponding boundary conditions are rigorously derived from a variational framework based on the Local Chan-Vese energy functional. The application of the level-set image segmentation approach enables to distinguish the cell wall material from the cell cavities. The cell material objects are subsequently segmented into axial cell objects and ray parenchyma cell objects that are oriented in the longitudinal and radial material directions of oak wood, respectively. This additional segmentation step facilitates the collection of statistical information on the inner cell dimensions and wall thickness of axial cells and ray parenchyma cells from images taken across principal material planes of the oak micro-structure. The performance and results of the image segmentation method are analyzed by using as input detailed micro-structural images of two representative oak samples containing a single growth ring, as obtained from X-ray micro-computed tomography experiments. The assessment of the robustness and convergence behaviour of the image segmentation method shows that the method converges very fast into a unique oak micro-structure that is independent of the initial configuration selected. The accuracy of the image segmentation result is shown through a comparison with the results obtained by two other image segmentation methods presented in the literature, and by visualizing and identifying small-scale morphological features within oak growth rings in great detail. The computational cost of the image segmentation method is evaluated by comparing its performance on CPU and GPU hardware. Additionally, a statistical analysis is carried out of the maximum and minimum inner cell diameters and the cell wall thickness of the various axial cells—fibers and axial parenchyma, earlywood vessels, latewood vessels—and ray parenchyma cells defining the micro-structure of the oak growth ring samples. The density histograms constructed for these geometrical parameters provide their statistical spread and most frequent value, which are quite similar for the two oak samples and are in good agreement with other experimental data reported in the literature. The oak micro-structures identified and characterized by the present image segmentation method may serve as input for dedicated finite element models that compute their mechanical/physical behaviour as a function of the geometrical and physical properties of the individual cells.

The damage zone and its effects on orthotropic deformations and elastic constants of beech blocks when subjected to compressive loading were investigated. The impact of surface treatment (sanded and speckled) on strain contours was examined first, followed by evaluating the effects of grain orientation, damage zone location, and load level on the length of damage zone. Subsequently, the effects of damage zone location on measured elastic moduli of beech blocks in various directions were evaluated. Finally, the factors on the elastic constants of beech blocks were investigated by considering six different strain-measuring methods. Experimental analyses found that sanded and speckled blocks had nearly identical strain contours when subjected to compressive loading in radial (R), tangential (T), and RT45° grain orientations, respectively. The length of the damage zone was significantly affected by grain orientation, load level, and damage zone location. The ratios of the length of the damage zone to the length of the tested block in different grain orientations ranged from 0.041 to 0.074 at proportional limit load and 0.045–0.078 at yield load. The mean ratio of each of the three elastic moduli measured in two ends of a tested beech block to one measured in its middle section ranged from 0.41 to 0.58. The length of the damage zone measured in tested beech blocks tended to show a negative correlation to its measured elastic moduli. These findings could provide a basic understanding of damage zones to analytical and numerical modeling of orthotropic deformations of beech wood.

The interaction of cellulose paper with water is a major hindrance to its broader application. This study, which introduces a novel approach to understand water vapor diffusion in both untreated and treated paper, aims to identify the diffusion coefficient, a crucial property in improving the hydrophobicity of paper. The treatment process utilized an aqueous solution of starch or starch modified with methyltrimethoxysilane (MTMS). While the initial sorption method is frequently used to determine the diffusion coefficient, this study found that it could lead to significant errors due to the non-Fickian behavior exhibited by lignocellulosic materials. This behavior causes that the hygroscopic equilibrium is not instantly obtained by surface of paper. It also induces slowing down moisture diffusion in its final stage due to molecular relaxation. For the first time, the modified convective boundary condition was introduced into the moisture diffusion model in paper materials. The results from vapor sorption experiments demonstrated this non-Fickian behavior, particularly at high values of air relative humidity. The study also revealed that the commonly applied first kind boundary condition is not applicable, even for thin paper samples, inhibiting the use of the initial sorption method for determining the diffusion coefficient. While the treatment with starch and MTMS significantly improved the hydrophobic properties of paper, it didn’t alter substantially its hygroscopic properties, potentially due to not blocking active sorption sites of cellulose fibers. This research underscores the need for further investigation into the chemical modification of cellulose fibers to improve the hydrophobicity of paper.

This study investigates lignin nanoparticles (LNPs) from spruce and Eucalyptus kraft lignins as sustainable additives for sunscreen formulations. The lignins and their nanoparticles were characterized using spectroscopic, chromatographic, and microscopic techniques and incorporated into oil-in-water sunscreen emulsions, where they were evaluated for UV-blocking efficiency, stability, and rheological properties. Results demonstrated that LNPs significantly enhanced UV protection, with spruce kraft lignin nanoparticles providing superior broad-spectrum coverage (280–400 nm) and an SPF of 12.94, compared to Eucalyptus lignin nanoparticles, which primarily absorbed in the UVB range (280–320 nm) and reached an SPF of 7.00. Additionally, LNPs improved emulsion stability through Pickering stabilization and enhanced rheological properties, making them promising eco-friendly and multifunctional sunscreen additives.

Pressurized heat treatment is an effective modification method for reducing the deformation recovery of compressed wood. In this study, the set recovery behavior, physicochemical and mechanical properties were studied for Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) subjected to surface compression treatment followed by pressurized heat treatment. The surface compression of wood was conducted in an open hot press with compression ratio of 33% as the first step, followed by pressurized heat treatment at 180 °C with different heating medium (nitrogen, steam, and nitrogen-steam mixed gas) under varying pressures of 0.1 MPa, 0.3 MPa, and 0.5 MPa as the second step. The results showed that the compressed layer density, the modulus of rupture (MOR), and the modulus of elasticity (MOE) of surface-compressed wood increased by about 55.56%, 56.60% and 30.90%, respectively, compared with the uncompressed wood. At higher heating medium pressures of 0.5 MPa with steam, the set recovery of surface-compressed (SC) wood induced by immersion and boiling in water was reduced by 88.03% and 70.11%, respectively, compared to the SC wood without pressurized heat treatment. Under the same medium pressure, SC wood treated with steam exhibited reduced set recovery compared to that treated with nitrogen and a nitrogen-steam mixed gas. It should be noted that incorporating nitrogen as a heating medium during the steam heat treatment process can reduce surface discoloration and improve mechanical properties while permanently fixing more than 70% of the compressive deformation of wood.

Humidity fluctuations are a leading cause of damage in wooden constructions. In the case of glulam products, the multitude of possible layups concerning pith locations, diverse material properties across wood species, and the high computational cost associated with multi-field analysis have constrained many research efforts to focus on one specific glulam layup, consequently limiting the generalizability of the findings. To address this challenge, Monte Carlo simulations were employed to assess the significance of various factors. Based on which, two levels of simplification are proposed. The first level reduces the multi-layer problem to a single-layer one by applying appropriate boundary conditions. It substantially reduces the simulation costs and consequently facilitates sophisticated damage analysis, revealing the varying damage pattern across different board types. The second level of simplification further reduces the problem to a single-element model, enabling an analytical estimation of moisture stress. This level of simplification elucidates how factors such as moisture difference, material rotational angle, and other material properties influence the moisture-induced stress. Most importantly, it facilitates a rapid estimation of the critical moisture fluctuation range and the preferred sawing location of boards for different wood species, which can provide guidance to the production of higher moisture resistant glulam.

This article provides an in-depth review of thermogravimetric analysis, highlighting the principle of pyrolysis and the analytical technique, as well as their significance for wood’s thermal degradation kinetics. The influence of the operating conditions and the material parameters on the thermal decomposition behaviour has also been discussed. Besides that, the comparative analysis of different treatments and operating conditions applied across various wood species has been thoroughly reviewed, where treatments such as torrefaction improved its thermal stability. Moreover, different approaches to improving wood’s thermal stability and their effects on the thermogravimetric analysis have been critically reviewed, and the mass loss, onset temperature, and char yield during the experiment show notable changes. This comprehensive review aims to provide insights into the important role of this analytical technique in assisting researchers and practitioners in selecting appropriate treatments to improve wood’s properties for safer and more sustainable use in a wide range of applications.

During brushing, friction between the brush and solid wood causes surfaces to become electrically charged through triboelectric effects. Wood, being a semi-conductive material, has its electrical conductivity influenced by factors such as moisture content, density, and anatomical structure. This study investigates the extent of triboelectric activation on wood surfaces using a wood brushing machine, with continuous detection of triboelectric surface field strengths. The effects of various wood modification technologies were assessed by comparing untreated control samples of two wood species, beech and poplar, to samples subjected to (1) densification, (2) steaming, and (3) thermal treatment at 120 °C and 180 °C. Positive triboelectric field strengths were recorded across all samples, with both nylon and steel wire brushes. The highest mean field strengths, 29.33 kV/m with the nylon brush and 7.86 kV/m with the steel brush, were observed in thermally treated at 180 °C and steamed poplar wood. Although surface field strength could not be directly correlated to density, a dependency on moisture content was established. These findings suggest that tailoring surface charges by controlling triboelectric effects could offer new opportunities for technical applications, such as chemistry-free primer modifications prior to wood coating.