European Journal of Wood and Wood Products最新文献

In this study, the effect of natural weathering on the physical and mechanical properties of two types of bamboo, Dendrocalamus asper, and Phyllostachys edulis was investigated. Twelve bamboo culms of each species were prepared, with six from each group treated with an 8% w/v disodium octaborate tetrahydrate (DOT) solution. The culms were half-buried in the soil for 33 months. After this period, the samples were removed, and the appearance condition of the exposed and buried parts was investigated regarding cracks and degradation. For microstructure characterization, the images were analyzed by SEM (scanning electron microscopy) to assess the changes in untreated and treated samples after natural aging. Physical and mechanical tests were carried out on all the samples, pre- and post-weathering. The results indicated no significant difference in the flexural strength of exposed parts between treated and untreated samples. For the buried section of both bamboo species, all untreated samples had rotten. Although the treated culms exhibited less degradation than the untreated ones, their use is not recommended, as the buried portions of the treated bamboo demonstrated more fragile behavior than the exposed parts. Despite the maintenance of mechanical properties in the exposed sections after ageing, the appearance of cracks caused by humidity variation and UV exposure could lead to weak points on the structure.

Developing eco-friendly, high-performance fibers requires a deep understanding of the interplay between chemical and physical properties and processing conditions. Peracetic acid (PAA) pulping offers a sustainable alternative to conventional methods, decomposing into water and acetic acid, while providing higher selectivity for lignin removal and lower energy demand. This study aims to optimize PAA pulping conditions to maximize lignin removal while retaining hemicellulose and cellulose, thereby improving fiber quality for applications in biocomposites and paper products. PAA pulping was conducted under systematically varied conditions, with temperatures ranging from 70 to 90 °C and reaction times from 60 to 180 min at a 3 wt% solid load. The conditions were selected based on the reaction spectrum of PAA, which becomes feasible for pulping above 70 °C. To operate at atmospheric pressure and avoid excessive degradation, temperature was limited to 90 °C. The study (1) investigates the effect of these parameters on pulping efficiency, (2) evaluates chemical composition and structural changes through lignin content analysis, carbohydrate profiling, and fiber morphology characterization, and (3) determines mechanical performance through tensile testing of paper sheets before and after hot pressing. Optimal results at 80 °C for 120 min led to increased inter-fiber bonding (106.13 Nm/g), significant hemicellulose retention, and substantial lignin reduction. These findings underscore the potential of PAA pulping as an energy-efficient, sustainable method for producing tailored holocellulose fibers with applications in biocomposites and other renewable materials, highlighting a promising strategy for valorizing wood byproducts and reducing carbon emissions.

Natural weathering gradually turns wood light grey over years, driven by exposure to sunlight, precipitation, and biological agents. Nontoxic chemicals have been used to accelerate artificial weathering-induced colour changes in wood. This study aimed to evaluate the effectiveness and underlying mechanisms of various surface treatment chemicals and a commercial silicon-based product in accelerating UV-induced colour changes in birch and aspen under artificial weathering conditions. Weathering was conducted by using an artificial weathering testing instrument with or without spraying the samples with water. Colour changes were measured with a portable spectrophotometer. Hyperspectral imaging data were included to visualise spatial variations of colour in wood samples. The use of water was a significant factor in determining the colour change in wood. Mostly photodegraded lignin constituents leached out of the wood with water spraying but remained if it was not used. The treatment chemicals caused distinct colour changes: Iron (II) sulphate caused dark grey staining, citric acid a unique red colour, sodium hydroxide darkening and brown hue, and hydrogen peroxide the most uniform colour. Commercial silicon-based product caused either little or no noticeable colour change over control samples. The greatest potential for colour change occurred during the first hours of artificial weathering. Spatial data of hyperspectral images allowed for more accurate estimation of variability over spectrophotometer data, and use of hyperspectral imaging in further research is therefore suggested.

The aim of the present work was to decrease formaldehyde emission and improve the dimensional stability of the wood-based panels bonded with urea-formaldehyde resin modified by deep eutectic solvent (DES) nanolignin. For this reason a deep eutectic solvent composed of Choline Chloride–ZnCl2 (ChCl-ZnCl2) was employed to pretreat nanolignin. The DES- modified and unmodified nanolignin were used to replace a part of urea (10%, 20%, and 30%) to prepare the lignin-urea- formaldehyde (LUF) wood adhesive. The changes in curing temperature and chemical structure of the LUF resin were determined by Differential Scanning Calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), respectively. The physico-chemical analysis showed that the UF resin with DES-modified nanolignin had higher solid content, viscosity and faster gel time than those using unmodified nanolignin. FTIR analysis indicated that the methoxy groups decreased and the phenolic hydroxyl groups increased by DES nanolignin modification. The DES-treated nanolignin LUF resin showed a lower peak temperature than those prepared using unmodified nanolignin. Moreover, the panels made from modified nanolignin presented a better mechanical strength (internal bond (IB) strength, flexural strength and flexural modulus) and dimensional stability as well as lower formaldehyde emission than those with unmodified nanolignin. The control UF resin presented a faster gelation time and higher viscosity than both unmodified and modified LUF resins. The mechanical strength of the particleboard bonded with the control UF resin was also better than the panels bonded with both modified and unmodified LUF resins. It should nonetheless be noted that the IB and flexural strengths of the panel bonded with a UF resin with 10 wt% DES-modified nanolignin were comparable to those bonded with the control UF resin. Based on these results, increasing the substitution degree of urea with DES-modified nanolignin significantly improved the dimensional stability and the formaldehyde emission of the particleboards bonded with a UF resin.

To obtain more information on possible reasons for the increased durability of surface charred wood, the chemical changes of surface contact-charred Norway spruce (Picea abies L.) were investigated by ATR-FTIR spectroscopy and pH value measurements. Temperatures of 300 °C, 350 °C and 400 °C were used to carbonize the surfaces of specimens for a duration of ≈ 3 min per surface. Measurements were conducted not only on the surface of the specimens but also on areas underneath the surface by removing material in steps. By that a “depth profile” of chemical changes could be created. Overall, the results of the applied methods seem to confirm the literature regarding the occurrence of different temperature zones in areas below the surface where different chemical changes occur. Concerning possible reasons for the increase in durability of charred wood, the formation of phenolic compounds during pyrolysis could be determined.

This study investigates the mechanical properties and the deformation pattern of silver birch (Betula pendula) and black locust (Robinia pseudoacacia) wood species under impact loading conditions. A drop-release impact testing machine tested the specimens in 3-point bending while a high-speed camera recorded the impact events. Subsequently, the recorded images were processed using the digital image correlation method to analyze deformation and strain behaviour. Basic physical properties of the specimens were determined, alongside test results such as maximum dynamic applied force, maximum deflection, and maximum normal tensile strain up to breakage. Also, the impact bending strength of the specimens was assessed. The maximum deflection and normal tensional strain of them were comparable. Both species had a similar impact bending strength value. Additionally, both species’ normal and shear strain distributions were determined for three levels of deflection in bending. This research contributes to a deeper understanding of these two wood species’ response to dynamic loadings, facilitating the development of more accurate predictive models and engineering designs.

High shape-stable phase change materials (PCMs) are critical for the application of thermal insulation or storage of building energy systems. In this work, the highly shape-stabilized PCM composites were prepared by using hierarchical porous bamboo supporting materials to stabilize polyethylene glycol (PEG). A rapid pretreatment method combining low-intensity microwave processing was employed for the first time to achieve porous bamboo with great structural integrity in which the PEG mass loading could be as high as 210%. The morphological, chemical, and hierarchical porous properties of bamboo supporting materials during the pretreatment process were systematically investigated. Due to the greatly developed pore structure and surface-active functional groups of bamboo supporting matrix, the formation of strong hydrogen bonds along with capillary actions between bamboo and PEG contributes to the excellent thermal storage properties of obtained bamboo-based PCM composites. The differential scanning calorimetry and liquid leakage tests of the composites exhibited high-stable shape and leak-proof performance with the phase change enthalpy high up to 100.6 J/g. This study provided a novel, rapid pretreatment method for bamboo and provided valuable insights for the future application of bamboo-based energy conservation materials.

Annual rings can record natural information such as regional temperature, humidity, and rainfall. However, they are often damaged by cracks, knots, and wormholes, making it difficult to obtain accurate data from them. In this study, O-Net is developed for the segmentation of annual rings in wood transverse sections containing cracks, wormholes, and knots. The O-Net framework is constructed by integrating parallel U-shaped encoder-decoder paths, utilizing convolutional kernels of two different sizes to capture multi-scale features of annual rings. Subsequently, the Efficient Channel and Spatial Attention (ECSA) mechanism is incorporated into the encoder to enhance the model’s ability to extract annual rings features near defects from both channel and spatial dimensions. Finally, a residual path is introduced through ablation experiments to refine the model’s architecture. The results demonstrate that O-Net effectively distinguishes between crack and knot boundaries and accurately segments annual rings, even in the presence of cracks and minor wormholes. O-Net is capable of extracting transverse sectional annual rings from wood containing cracks, wormholes, and knots, addressing the limitations of traditional methods in accurately extracting damaged annual rings with defects.

Wood samples treated with ultraviolet (UV) radiation (200 h, 80 °C) and mild thermal treatment (200 h, 80 °C) were stored under laboratory conditions in complete darkness for 14 years. 15 wood species used by the carpentry industry were involved in the tests. Colour changes were monitored and presented using the CIE L*a*b* colour measurement system. Samples with low extractive content (e.g. spruce, poplar, maple and ash) presented the greatest increase in redness and yellowness during UV irradiation. Cherry, larch and American cherry showed the best stability against photodegradation. These tree species have the highest natural extractive content responsible for redness. Both UV irradiation and the subsequent natural ageing in dark conditions resulted in a greater increase in redness than in yellowness. Long-term storage in total darkness resulted in much greater redness and yellowness increases for UV irradiated samples than for slightly thermally treated samples. Thermal treatment at 80 °C followed by the long-term storage in darkness produced only small alterations in lightness, redness and yellowness.

Wood-based panels bonded with urea-formaldehyde (UF) adhesive serve for construction and furniture manufacturing with excellent physical properties and cost-effectiveness. However, the moisture susceptibility of wood limits its applications and service life. The paraffin emulsions can provide waterproofing, whereas excessive paraffin weakens the bonding strength of wood-based panels. In this study, the modified paraffin with superior dispersion was prepared and the accompanying effects on the bonding performance was investigated. Results indicated that the modified paraffin emulsion with a mean particle size of 3.17 μm, which decreased by about 84.6% as compared to the commonly used paraffin. FTIR, XPS, SEM, and contact angle measurements showed that the modified paraffin reduced hydrophilic groups and enhanced the hydrophobicity. The commonly used paraffin particles are prone to agglomerate, which reducing the adhesive penetration depth of UF adhesive into wood. After modification, the penetration depth of UF adhesive into wood was increased by about 52.3%. The improved permeability of UF adhesive into wood contributed the highest tensile shear strength of glued wood with modified paraffin under both dry and wet conditions. Shear strain distribution during the test indicated that the modified paraffin enhanced stress transfer capacity within the glueline, improving mechanical performance. These findings are beneficial to develop the wood-based panels with high bonding performance and moisture-resistance for outdoor applications.