European Journal of Wood and Wood Products最新文献

The use of aluminum sulfate (AS) as a chemical treatment for plant fibers aims to protect them against the aggressions of the alkaline environment provided by cement. This research aimed to understand the effects of treatment with AS (chemical modification) at concentrations of 0%, 4% and 11% on the surface of Kraft pulp of Pinus spp. and to evaluate the composites generated on the 28th day of curing and after 200 cycles of accelerated aging. The results suggest that AS is a surface modifying agent and will be homogeneously deposited on the surface of plant fibers. In addition, the experimental data showed that treatment with AS reduced water absorption by approximately 3% and apparent porosity by 10% in cementitious composites. In contrast, the limit of proportionality increased with both AS concentrations. Furthermore, the modulus of elasticity of the composites produced with the fibers treated with AS increased considerably in relation to that of the fiber-cement sample with 0% AS. The modulus of rupture (MOR) of the 4% AS treatment sample was considerably greater than that of the control sample, both on the 28th day and after the aging cycles. On the other hand, no considerable changes were observed in the MOR of the composites produced from fibers treated with 11% AS compared to the control. The specific energy of the fiber-cement composites with 4% and 11% AS was considerably lower than that of the control sample. These data reflect the methods of applying cementitious composites, which can be used in the manufacturing of covering tiles that yield better results in terms of the modulus of elasticity (MOE). On the other hand, those composites that obtained higher MOR and specific energy (SE) values may be suitable for the production of both tile and flat plates.

The recent publication of the European Regulation on deforestation, linked to the import and export from the European Union (EU) of certain commodities and products associated with deforestation and forest degradation, controls sustainable and legal sourcing of wood and wood-based products in EU. In this context, the accurate verification of wood species and their origin has become increasingly crucial. In this work, a multispectral camera was adopted to retrieve high resolution remotely sensed imagery of different wood samples exploring the spectrum between 440 and 860 nm. Eighteen wood species spectra were investigated. Starting from these spectra, linear discriminant analysis (LDA) proved that the band at 665 nm is the first discriminative feature, followed by 490 nm and 560 nm, respectively. Bands at 783 nm or higher wavelengths, i.e. the NIR region, discriminate selected species poorly. Using the first 4 linear discriminants, a classification of wood species was performed using the minimum Mahalanobis distance algorithm. The majority of species showed class accuracies between 0.7 and 0.9. However, some species showed poor performances. Cluster analysis involving all available spectra proved that the higher classification errors occurred between species of the same spectral cluster. This work shows the potentialities of adopting cheap and rapid screening tool (cameras) for separating selected wood species opening new scenarios to support industrial and commercial control processes.

Unlike the conventional resin tapping processes throughout long periods of time or the complete life of the trees, in which the cellular and physical–mechanical characteristics of the whole wood could be modified, the resin tapping system, only in the last years before the ideal-timber cutting shift, shows no significant influence on some physical–mechanical timber properties. Samples of one-face and two-face resin-tapped trees were compared with samples of untapped tress. Using wood density as a reference property in solid wood and after checking the normality of the samples, no significant differences were observed. Therefore, according to the results of this work, the tapping process in the last three years combined with timber logging should not affect or limit its use as solid wood. For a better adjustment in the study, untapped wood and wood from resin tapping logs of the furthest (upper) and closest (lower) part from the tapping area were compared. The wood density mean values were, respectively for the upper and lower areas: 557 kg/m³ and 570 kg/m³ for one-face resin-tapped wood; 567 kg/m³ and 564 kg/m³ for two-face resin-tapped wood; and 556 kg/m³ and 560 kg/m³ for untapped wood. The tapping techniques used in the study are identified as common extract methods, and, according to the results, adequate added value with multifunctional forest use without a potential depreciation in the mechanical properties was found.

In this paper, a dynamic vapor sorption analyzer in conjunction with the Dino-Lite Edge Digital Microscope was utilized to study the moisture sorption and thickness variation characteristics of the surface and core layers of impregnated paper coated fiberboards (IPCF) and its substrate high density fiberboards (HDF) at different temperatures. Results showed that the equilibrium moisture content (EMC) of both the surface and core layers of IPCF was reduced by the impregnated paper coating, and their dimensional stability as well as dimensional recovery performance after swelling was enhanced. A different phenomenon from previous studies was observed, the EMC of both the surface and core layers of IPCF and HDF increased with the increase of temperature. It can be affirmed that this phenomenon is not related to capillary condensation water. In addition, both the surface and core layers of IPCF and HDF exhibited moisture sorption hysteresis and swelling hysteresis during the moisture sorption cycle, both of which showed opposite responses to temperature. The sorption hysteresis and swelling hysteresis were affected by the degree of melamine-urea–formaldehyde (MUF) resin crosslinking and porosity, respectively. The higher the crosslinking degrees of the MUF resin in fiberboard, the greater the absolute hysteresis; swelling hysteresis is negatively correlated with porosity.

Cryptomeria japonica (Japanese cedar) in Japan plantations are aging, and the main supply of timber in the market is shifting from small- and medium-diameter to large-diameter logs. The effective utilization of these logs has become an important issue in the timber industry. When producing timber-without-pith from large-diameter logs, an unavoidable warp occurs because of the release of residual stress within the logs. Utilizing high-temperature drying with a load on these timbers has achieved significant drying effects, and the residual stress-induced warp was corrected. However, high-temperature drying has drawbacks, such as high energy consumption and the potential for thermal degradation. We applied low-vacuum-medium-temperature drying (LVMT-drying, 10 days, 40 kPa, 80/55 °C (DB/WB)—90/65 °C (DB/WB)) with load (650 kgf/m²) to the stacked timber sawn from large-diameter logs to address these questions. When LVMT-drying was successful, residual stresses in timber-with-pith were reduced to nearly zero, and warps in timber-without-pith were reduced to less than 8 mm, i.e., below the Japan Agriculture Standard "Level 1" for 4000 mm timber, and the acceptance rate for "Level 1" increased from 45% (green timber) to 85% (treated timber) in the most successful sample. LVMT-drying is a practical drying method for timber from large-diameter logs because it is effective in reducing residual stress and correcting warps while shortening the treatment period and avoiding thermal degradation.

The growing demand for polymeric materials has made them significant in both industry and the environment, and the task of making them sustainable is becoming increasingly challenging. Cellulose presents an opportunity to minimize the effect of nondegradable materials. Cellulose nanofibers (CNFs) are a class of cellulose fibers with superior performance due to their high strength and stiffness combined with low weight and biodegradability. This work aimed to produce composites using low-density polyethylene (LDPE) as a matrix and CNFs from Pinus sp. (Pinus) and Eucalyptus sp. (Eucalyptus) as reinforcements. The CNFs were obtained by mechanical defibrillation of the cellulose, and subsequently, the water was removed by centrifugation to produce a master with CNFs and LDPE using a thermokinetic homogenizer. The master was milled and blended with LDPE to obtain booster concentrations of 1, 2 and 3% by weight (wt%). To characterize the composites, tensile and flexural tests and thermal and rheological analyses were performed. An increase of between 3 and 4% in the crystallinity of the composite was observed with the addition of Pinus CNF, and a decrease of 2 to 3% in the crystallinity index was observed with the addition of Eucalyptus CNF. The thermal stability increased for all the compositions. For the mechanical properties, increasing the CNF content increased the stiffness and tensile strength. In general, this process is an effective alternative for producing composites of LDPE with cellulose nanofibers.

In recent years, laser wood processing has become increasingly common. However, to ensure the longevity of wooden materials, it is necessary to cover their upper surfaces. This study investigates the effects of laser beam-induced changes on various preferred types of wood surface treatments using CNC laser wood processing technology. Beech wood test specimens were coated with cellulosic varnish, synthetic varnish, polyurethane varnish, and acrylic varnish and their layer thickness was measured. Based on the data obtained, it was evaluated how different varnish layers affect kerf depth and upper kerf width in laser cutting compared to control samples without varnish. Additionally, the impact of varnish layers on laser wood engraving was examined. The findings suggest that certain varnishes can compromise the laser cutting performance of the control samples, while others can enhance it. Furthermore, all varnish types positively influence laser cutting performance by reducing the upper kerf width of the laser cutting notches. However, in laser wood engraving, all varnish types weaken the laser engraving performance.

The aim of this study was to compare the antioxidant capacity of hydrophilic extracts of different tissues of wet-hearted silver fir (Abies alba Mill.) logs. Wet heart is a wood defect of silver fir and lowers the value of wood. The exploitation of extractives could increase utilization and financial returns. The bark, sapwood, heartwood and knotwood were investigated by using two green extraction methods: ultrasound assisted extraction (US) and accelerated solvent extraction (ASE), with aqueous ethanol as solvent. Total extractive content (TEC), total polyphenol content (TPC) and antioxidant capacities (FRAP, DPPH, ABTS) from the extracts were determined and compared. The highest contents of total hydrophilic extractives were measured in knotwood (23.07%, ASE) and bark (10.31%, ASE), and the lowest values were determined for sapwood (2.00%, ASE) and heartwood (3.56%, ASE). The ASE method resulted in significantly higher TPC (0.65–10.58%) than the US (0.46–9.19%) method. Nevertheless, the simplicity of instrumentation and costs can make US also a potential candidate for future extraction and utilization. The highest antioxidant capacities were measured in knotwood (FRAP: 159.75 mg AAE/g, ABTS: 316.15 mg TE/g, DPPH: 189.23 mg TE/g) and bark (FRAP: 159.75 mg AAE/g, ABTS: 126.81 mg TE/g, DPPH: 74.52 mg TE/ g) extracts, prepared with ASE, which complements well the existing literature data on silver fir extractives. The knotwood and bark of wet-hearted silver fir is an abundant source of antioxidant polyphenols, whereas sapwood and heartwood are poor in these extractives and potentially unsuitable for the valorization by the extraction of natural antioxidants.

The aim of the research was to investigate the possibility of producing bio-composite particleboard with a density reduced to 500–550 kg/m³, containing 25% and 50% of walnut shells. In addition, the study also concerned the possibility of using these materials in sandwich systems. Based on the results, it was found that partial replacement of wood particles with ground shells leads to a significant reduction in the strength of the boards bonded with urea-formaldehyde (UF) resin. However, the implementation of a hybrid gluing method consisting of gluing wood particles with UF resin and walnut shells with 4,4′-methylenediphenyl isocyanate (pMDI) caused a significant improvement in the strength of the boards, especially for the variant with the highest shells content. Despite that, the manufactured materials still do not meet the requirements for furniture boards. The next step of the research has shown that these boards can perform well as a core layer in the sandwich boards covered with high-strength HDF boards. Moreover, it was found that increasing the share of walnut shells positively affected the dimensional stability of the resultant boards (thickness swelling and water absorption). However, substitution of wood with shells accelerated the ignition and flameout times of the boards. It increased the heat release without significantly affecting the percentage loss of the boards’ mass during exposure to fire.

The importance of creating eco-friendly and health-conscious materials has become paramount in striving to attain long-term development goals. For the past decades, constant efforts have been made to tackle the issue of formaldehyde release from wood-based panels which, to date, are still mainly produced from unsustainable synthetic adhesives. In the pursuit of sustainable and environmentally responsible adhesive solutions for the wood industry, sodium bisulfate, sodium bisulfite, and sodium nitrite were used under different heat treatment conditions as crosslinkers for canola protein-based bio-adhesive formulations. The developed adhesive formulations showed outstanding mechanical properties, with a viscosity below 4000 mPa/s despite the relatively high solid content, as well as excellent bonding performances. The one-layer particleboards bonded with the canola-based adhesive demonstrated outstanding mechanical properties, with the internal bonding and the bending strength values surpassing 0.60 N/mm² and 10 N/mm², respectively. Notably, the sodium nitrite-crosslinked variants exhibited significantly superior performance compared to the UF-bonded control boards. Longer incubation times generally improve bonding strength, with sodium nitrite showing the most pronounced effects. The results of this research showcase not only the possibility of developing a plant protein-based wood adhesive with high solid content, but also the potential superiority of canola protein-based wood adhesives when compared to conventional, synthetic counterparts. These findings offer valuable insights for optimizing bio-based adhesives in wood composite manufacturing, highlighting sodium nitrite as a promising crosslinker for enhancing the adhesive’s performance.