Wood Science and Technology最新文献

During the dehydration of waterlogged archaeological wood (WAW), shrinkage inevitably occurs due to capillary force and hydrogen bond recombination as WAW loses free and adsorbed water. Existing drying techniques, including solvent displacement, freeze-drying, and supercritical fluid drying, only take effect by reducing or eliminating the surface tension of liquid. Nonetheless, the contribution of hydrogen bond recombination in shrinkage has long been neglected and a countermeasure concerning this problem is needed. In this study, we propose a simple aqueous phenylboronic acid (PBA) treatment that can help improve dimensional stability and reduce hygroscopicity of WAW. Analysis by Fourier transform infrared spectroscopy, density functional theory calculation and dynamic vapour sorption reveal that PBA can incorporate with hydroxyl groups (–OH) on cellulose through coordination and hydrogen bonds, occupy the water-cellulose binding sites, and possibly inhibit the formation of hydrogen bonds between adjacent cellulose chains.

The transient dimensional changes during hygro-expansion and hydro-expansion of freely and restrained dried, softwood and hardwood sheets and fibers is monitored, to unravel the governing micro-mechanisms occurring during gradual water saturation. The response of individual fibers is measured using a full-field global digital height correlation method, which has been extended to monitor the transient hydro-expansion of fibers from dry to fully saturated. The hygro- and hydro-expansion is larger for freely versus restrained dried and softwood versus hardwood handsheets. The transient sheet-scale hydro-expansion reveals a sudden strain and moisture content step. It is postulated that the driving mechanism is the moisture-induced softening of the so-called ”dislocated regions” in the fiber’s cellulose micro-fibrils, unlocking further fiber swelling. The strain step is negligible for restrained dried handsheets, which is attributed to the ”dislocated cellulose regions” being locked in their stretched configuration during restrained drying, which is supported by the single fiber hydro-expansion measurements. Finally, an inter-fiber bond model is exploited and adapted to predict the sheet-scale hygro-expansion from the fiber level characteristics. The model correctly predicts the qualitative differences between freely versus restrained dried and softwood versus hardwood handsheets, yet, its simplified geometry does not allow for more quantitative predictions of the sheet-scale hydro-expansion.

Considering the bioactive composition and therapeutic interest of Ficus carica, much research has been conducted on its fruits and leaves. However, there has been relatively little investigation regarding the wood bark, despite its potential as a rich source of phytochemical compounds with diverse biological activities. The aim of this work is the determination of the phenolic composition of the wood bark extracts of F. carica from three cultivars (Aberkane, Aghanime, and Bakour) and the assessment of their potential cytotoxicity and bioactive capacities such as antioxidant, anticancer, and anti-inflammatory activities. The phytochemical compounds were identified and quantified using UPLC-ESI-MS. The results revealed that Aberkane wood bark cultivar had the highest content of total polyphenols and ascorbic acid, while Aghanime cultivar had the highest content of flavonoids. The wood bark of the Aberkane cultivar exhibited the highest DPPH and ABTS scavenging activities (48.55% and 71.81%, respectively). This extract exhibited strong cytotoxic effects against cancer cell lines MCF-7 (IC₅₀ 143.30 µg/mL) and carcinoma HepG2 (IC₅₀ 240.18 µg/mL), as well as potent anti-inflammatory activity demonstrated by the BSA assay and inhibition of NO production in RAW 264.7 cells. Aghanime wood bark extract exhibited the highest ORAC value (446.078 µmol TE/g). However, the Bakour wood bark cultivar was particularly noteworthy for its iron-chelating properties. The UPLC-ESI-MS analysis revealed the presence of various phenolic compounds, notably chlorogenic acid and rutin. These findings demonstrate that the wood bark extract of fig possesses a diverse range of beneficial biological activities, which are associated with its phytochemical composition.

Trees living in subfreezing environments for extended periods are susceptible to brittle fracture and freezing injury, which limits wood quality and final utilization. This study investigates the effects of temperature and cooling rate on the freezing of water in wood using dielectric spectroscopy. Dielectric parameters such as dielectric constant, loss factor, and relaxation strength were observed during cooling process of wood. The effects of subzero temperature and cooling rate on the dielectric parameters were found significant. The dielectric parameters at a slow-cooling rate were generally higher 12%∼143% than those at a fast-cooling rate. During the cooling process from 20°C dropped to − 80°C, the freezing process of water in wood was divided into four stages based on the dielectric parameter change and its impact on wood cell wall was characterized using SEM and DSC methods. The findings of this study provide the basis to explore the freezing behavior of water in wood and further to determine the cause of freezing injury in trees.

The low efficiency of montmorillonite (MMT) as a nano-flame retardant has limited its widespread application. In this work, a clay-based flame retardant was developed by modifying MMT with ammonium polyphosphate (APP) and 3-Aminopropyltriethoxysilane (SCA). Subsequently, wood composites treated with the clay-based flame retardant were prepared, and their char formation and smoke suppression behavior were investigated. MMT sheet effectively absorbed a significant amount of APP, and the broken edges of the sheet were successfully grafted with SCA. This promoted the formation of polyphosphoric acid and improved the interface compatibility among the components of wood composites. The clay-treated wood composites exhibited a reduction in total heat release (by over 27.0%) and a significant increase in char residues (up to 111.9%) compared to the control. Moreover, the second peak of the smoke production rate and mean CO yield were decreased by up to 43.2% and 63.2%, respectively. The formation of continuous, compact, and cross-linking (e.g. C-Si and Si-O-P) char layers endowed wood composites with thermal insulation, delayed the spread of flammable or poisonous gases (e.g. CH₄ and CO), and suppressed the release of toxic smoke. Therefore, a simple and effective method for fabricating a clay-based flame retardant was proposed, which holds potential application in wooden construction materials.

The aim of this study is to investigate the effects of different cellulose nanofibers (CNF, 0–20% w/w) and aluminum oxide nanoparticles (Al₂O₃ NPs, 0–4% w/w) concentrations on the properties of deacetylated konjac glucomannan (DKGM) base film, as well as the protective performance of DKGM-based composite film on wood. The addition of CNF primarily improves the mechanical properties of the film. Compared to the KGM base film, the DKGM/CNF composite base film (DKC) exhibits excellent tensile strength and elongation at break, with increases of 44.39 MPa and 19.87%, respectively. After application to the wood surface, the glossiness of the wood increased by 43.48%, and the moisture absorption dimensional change rates reached 0.07% (radial) and 0.11% (tangential), while the moisture absorption coefficients decreased to 0.008 (radial) and 0.019 (tangential). The addition of Al₂O₃ NPs primarily improves the film’s resistance to ultraviolet light and water. Compared to the DKGM base film, the water contact angle, water solubility, and water vapor barrier performance of the DKGM/ Al₂O₃ composite base film (DKA) significantly improved. When applied to the wood surface, the wood wear resistance and aging resistance increased by 62% and 69.67%, respectively. Therefore, DKGM base films doped with CNF and Al₂O₃ NPs have broad development prospects in the field of wood protection.

Shorter processes and lower temperatures are critical to reducing thermally modified wood costs. In this study, the exogenous H₃PO₄ was infiltrated into poplar (Populus × euramaricana) and then heated at low temperatures of 130–170 °C to speed up the thermal modification process of wood with better performance. The hygroscopicity was analyzed by dynamic vapor sorption detection and its constituents of modified wood were characterized by high-performance liquid chromatography and solid-state CP/MAS ¹³C NMR. The results showed that acid combined with low-temperature thermal modification (acid-LTM) resulted in lower equilibrium moisture content compared with the high-temperature thermal modification (HTM) wood. The addition of H₃PO₄ triggered severe degradation of the carbohydrates in the wood, and the mass loss of cellulose and hemicellulose were 11.9% and 24.1% when modified with 3.0% H₃PO₄ at 150 °C, respectively, thereby reducing the quantities of water sorption sites. Besides, the degradation products of carbohydrates crosslinked with the thermally stable lignin to form “pseudo-lignin” substances, leading to an increase in the lignin content of acid-LTM wood. The increase in the crystalline index and crystallite size of cellulose in acid-LTM wood was also conducive to reducing the wood hygroscopicity. The better hydrophobicity of acid-LTM poplar was further verified by its decrease in the water sorption site density and the theoretical OH content compared with HTM wood and unmodified wood. This study will offer a potential process to manufacture thermal-modified wood at a low cost.

Holocellulose fibers provide great potential to make paper with high performance. However, inappropriate reaction conditions may limit its improvement in paper performance due to the lack of sufficient research data. In this work, paper is prepared from the birch holocellulose fibers based on peracetic acid treatment and the papermaking process. The features of resulting holocellulose fibers are evaluated for different peracetic acid treatment conditions such as temperature and time. It reveals that high temperature and long treatment time lead to the degradation of hemicellulose/cellulose and the destruction of fibers, which further results in the poor mechanical performance of paper. By optimization for the treatment condition of holocellulose fibers, the corresponding paper exhibits the highest tensile strength (93 MPa), good bursting strength (601 kPa), and tearing strength (647 mN). The determination of optimum conditions will provide guidelines for the industrial production of holocellulose fibers and paper.

The interaction between bamboo and moisture leads to mechanical properties and dimensional changes, which is an important issue affecting the processing and utilization of bamboo. Fibers and parenchyma cells are the main components of bamboo, and there are differences in hygroscopicity, but the main factors influencing the differences are unclear. Therefore, this study investigated the relationship between cells, chemical component content, pores and hygroscopic behavior of fibers and parenchyma cells, and analyzed the moisture types and the interaction of functional groups with moisture. The results showed that there was little difference in hygroscopicity between fibers and parenchyma cells at low relative humidity. At humidity greater than 60%, the difference in moisture absorption was significant. The maximum difference in moisture content between fibers and parenchyma cells was 8.81%. At low relative humidity, the abundance of pores did not show advantages, and the humidity had a greater effect on moisture content of parenchyma cells. In addition, moisture absorption at low relative humidity was selective, with moisture favorably bound to lignin. This study, by analyzing the differences in moisture types and absorption sites of fiber and parenchyma cell, could provide a better understanding of the binding mechanism between bamboo and moisture, to provide a theoretical basis for the subsequent research on hygroscopicity of bamboo.

Bamboo pith ring (BPR) is regarded as a particular tissue affecting bamboo processing and is usually discarded, resulting in waste and low utilization of bamboo. To improve the utilization of bamboo and make full use of BPR, the fundamental properties, including morphology, chemical properties, and mechanical properties of BPR by confocal laser-scanning microscope, SEM, IR-image, and nanoindentation, were investigated in this study. On the macroscale, the stone cells in BPR are round or square and closely arranged, and the average thickness of BPR is 404.6 μm. On the cell scale, with the increase in distance from the pith cavity, stone cells show different shapes and sizes. On the cell wall scale, the stone cell in BPR show a multi-layer structure with alternating thick and thin walls, and there are dense pits on the wall layer. Stone cell is mainly composed of cellulose, hemicellulose, and lignin, and hemicellulose and lignin contents are higher than parenchyma cell. The elastic modulus and hardness of the stone cell wall were 6.98 GPa and 491.8 MPa, respectively. Studying BPR morphology, chemical, and mechanical properties are expected to lay a foundation for, among others, bamboo gluing, mechanics research, and drying cracking.