European Journal of Wood and Wood Products最新文献

Manufacturing green and sustainable bio-based adhesives is an effective strategy to alleviate both serious energy and environmental issues. Herein, based on the aldehyde–amine covalent reaction between dialdehyde starch (DAS) and polyamine (PA_6N), a hyperbranched crosslinked starch-based adhesive was prepared, which overcomes the disadvantage of poor water resistance of conventional starch-based adhesive. The imine groups (C = N) and aminal groups (N–C–N) produced by the reaction of dialdehyde starch and polyamines stably “weld” the molecular chains of dialdehyde starch and polyamine. In addition, the dense cross-linking network formed by the molecular chains stacking and entanglement also plays a crucial role in enhancing the water resistance of the adhesives. The FTIR, XPS, and ¹³C NMR indicated that the imine and aminal covalent bonds were formed between the starch molecular chain and the polyamine. The dry bonding strength of the modified starch adhesive reached 2.12 MPa, which was increased by 162% compared to the natural starch adhesive. The wet strength of the adhesive after 63 °C of hot/boiling water soaking for 3 h broke from 0 to 1.92/1.34 MPa. The proposed DAS-PA_6N starch-based adhesive has the advantages of low cost, high performance, and green sustainability, suggesting broad application prospects in aldehyde-free bio-based wood adhesives.

Termites are a major cause of damage to wood, and the use of synthetic insecticides for their control constitutes a significant challenge to environmental health. This study assessed the damage to the wood of four Eucalyptus species upon exposure to subterranean termites, as well as the efficacy of three plant oils and a synthetic wood preservative. The physical properties responsible for wood resistance were determined using standard procedures. Pearson correlation, Analysis of Variance (ANOVA), and Tukey’s Honestly Significant Difference (p < 0.05) were used for data analysis. The results showed that the greatest and least wood damage was recorded in Eucalyptus tereticornis and Eucalyptus cloeziana, respectively. The wood hardness recorded in E. cloeziana was higher than in E. tereticornis and correlated significantly with the percentage of wood loss. Solignum, a synthetic wood preservative, reduced the wood loss due to termite infestation more effectively than the plant oils. Oil extracts from neem seeds, Jatropha seeds, and palm kernels significantly reduced wood loss compared to the control treatment. However, the potency of the plant oils decreased over time. The wood of E. cloeziana demonstrated a high level of resistance against termite infestation, and neem oil, Jatropha oil, and palm kernel oils possess the potentials as alternatives to synthetic wood preservatives for wood protection.

The paper presents a complex solution for testing loaded structural-sized glue laminated timber and innovative wood-carbon fibre reinforced polymers (CFRP) composite beams exposed to local fire. It shows the entire procedure from predicting a static behaviour and a combustion time (from reaching 300 °C temperature of the element up to its fracture) of the tested elements, designing and building an experimental stand, through conducting preliminary tests and discussing the results. The research included combustion of three glue laminated timber (BSH) and three wood-CFRP composite (BSH-CFRP) structural-sized beams in the most loaded section (region of highest bending moment) under three-point bending. A furnace was set under the centre of the beam on one-third of its span. The dimensions of the basket are based on physical properties of firewood providing proper burning conditions of the elements. The self-designed and self-constructed experimental stand enabled applying high load and provided a stable loading during local fire exposure. The preliminary tests showed that using CFRP tapes inside the section may both increase or decrease fire resistance of wooden members depending on the width of wood material covering CFRP tape. CFRP tapes provide a different nature of beam failure, which is changing from sudden fracture (BSH) to plastic flow of the material (BSH-CFRP).

Tracheid effect is a well-known phenomenon, widely studied and industrially applied for softwoods. However, studies of this effect on Malaysian tropical hardwoods are scarce to non-existent. This paper investigates the light scattering characteristics of light red meranti (LRM) (Shorea spp.), Malaysia’s most common commercial timber species. Diode laser dot projectors at wavelengths of 650 nm (red) and 808 nm (near infrared, NIR) were used, imaged by a Hikrobot MV-CE200-10UC colour industrial area-scan camera. The laser dots on the wood were imaged at 30° intervals. Eccentricities and angles of the ellipse generated by the tracheid effect were obtained using principal component analysis (PCA). Red channel of the images scored the best results for both NIR and red laser for LRM. Angle detection accuracy and linearity for NIR laser on milled LRM surface (root mean squared error, RMSE = 2.892°, coefficient of determination, R² = 0.9996) were comparable to those of pine (RMSE = 1.5330°, R² = 0.9998). For rough sawn LRM surfaces, NIR performed poorly with large errors (RMSE = 11.4948°, R² = 0.9887). The red laser fared mediocrely with LRM milled surface (RMSE = 7.8922°, R² = 0.9947) compared to pine (RMSE = 1.1582°, R² = 0.9997), and was practically unusable on rough LRM surfaces. Approximation of grain directions using NIR lasers on rough surfaces, or 650 nm red lasers on milled surfaces, is also possible albeit with substantially degraded accuracy. This study informs future studies of the viability of using tracheid effect to research on related characteristics and properties of LRM using visual methods.

Wood materials from tropical forests are particularly prized for their characteristics and properties. In this regard, wood from the West African forests comes up with an established reputation in the international wood market. Despite this, there has been little research on the properties of timber wood species in this geographical region. This study aims to characterize the main chemical contents and molecular structures of four timber wood species (Daniellia oliveri, Isoberlinia doka, Khaya senegalensis, and Pterocarpus erinaceus) from forests in southern Mali. The wood samples used in this study consisted of 11 wood cross-sections taken from individual planks of commercialized timber originating from three different localities (Kita, Kéniéba, and Sibi). Fourier transform infrared spectroscopy was applied to record 20 spectra per cross-section over 10 cm in the heartwood region. Next, a database made of 220 infrared spectra was analyzed using relative absorbance, FTIR ratios, and multivariate data analysis methods. The results showed that the molecular structure and functional groups in carbohydrate and lignin compounds are suitable to characterize the studied wood species. FTIR signals of polysaccharide compounds with crystalline structures are more abundant in the wood samples of D. oliveri, whereas wood samples of P. erinaceus contain the highest relative amount of lignin compounds with guaiacyl structures. Hemicellulose components are relatively more prolific in I. doka as well as in K. senegalensis. Finally, the results provide valuable details about the chemical properties of the studied wood species, which may be relevant for the assessment of the quality and for the definition of the adequate end-uses.

The lack of quantitative methods for surface-checking measurements may hinder improving the product characteristics of engineered wood flooring products built with sliced top-layer lamellae. This study evaluated the digital image correlation method for its applicability to surface checking measurements in engineered wood flooring elements with the top-layer comprising the plain sliced lamellae of oak (Quercus spp.) species with nominal thicknesses of 1.5–4.5 mm. The method involves observing full-field surface displacements of the sliced lamellae-based wood flooring specimens subjected to an accelerated sorption/desorption cycle. Detection of surface checks relates to discontinuities in surface displacements which can be interpreted from the output strain data as strain peak regions. Additionally, a surface-checking index was defined to describe the extension of surface-checking. Exposure tests were performed on a combination of coating presence and a different number of testing cycles. The main findings provide insight into the method procedure parameters, such as exposure duration, climate conditions, analysis parameters and recommendations regarding the digital image correlation setup settings and specimen manufacturing.

Flattened bamboo has a higher material utilization rate and a lower content of adhesives, which exhibits enhanced stiffness and anti-hygroscopicity, compared with original bamboo. To promote flattened bamboo to be an engineering material, the dimensional stability of flattened bamboo is required to be further improved. In this study, natural tung oil was used to modify flattened bamboo under different temperatures (23–160 °C). It was found that the water-swelling and shrinkage of the flattened bamboo reduced more than 43.00% and 20.93%, respectively, after modification with tung oil at 160 °C. The tung oil film was identified to adhere to the cell lumen, intercellular space, cell wall layer and pit channel. Furthermore, many pits in vessels were shrunk, and the crystallinity of cellulose was increased during modification of flattened bamboo by tung oil treatment at 100–160 °C. Altogether, these findings suggest that tung oil improves the dimensional stability of flattened bamboo by delaying water transport in the transverse direction and retarding the bonding of water molecules to the cell wall. Additionally, tung oil modification has little impact on the visual effects of flattened bamboo.

Packaging materials play the role of isolation and protection in product storage, transportation, sales, and other links. However, wood fiber-based and polymer-based packaging materials used for carrying, packaging, bedding, supporting, and reinforcing goods have the drawback of low ignition point, and flame retardant treatment is required for these materials. Aiming at the flame retardant treatment of wood fiber-based packaging materials and polymer-based packaging materials, the application of biobased flame retardants limits or eliminates the detrimental effects on wellbeing and environments which are usually the result of petroleum-based counterparts. In this paper, combined with the development status of biobased flame retardants in the flame retardant treatment of packaging materials, different biobased flame retardants are classified according to the types of functional groups, like bio-based polysaccharide, amino acid flame retardants, phosphate, and phenolic flame retardants. The modification methods, decomposition process, and flame retardant mechanism of different biobased flame retardants have been analyzed. What’s more, the advantages and problems in the development and application have been summarized, and new ideas are provided to develop biobased flame retardants with better performance and more environment-friendliness.

Sorption properties of paper products are important when applying paper as the packaging material. Hydrophobicity, i.e. reduced affinity of paper surface to liquid water, is of particular importance from the point of view of the direct impact on packed goods. However, hygroscopicity of the material is significant during storage of goods. The analysis of changes in the hygroscopic properties of paper products induced by the treatment with silane modified starch was presented. The results on the hygroscopicity of treated paper were related to the previously published results on the hydrophobicity. The discrete values of equilibrium moisture content allowed constructing adsorption and desorption isotherms. The three-parameter Guggenheim, Anderson, and De Boer (GAB) model, the four-parameter Generalized D’Arcy and Watt (GDW), and Yanniotis and Blahovec (Y-B) sorption isotherm models were used to quantify the hygroscopic properties for all options of untreated and modified paper samples. The effectiveness of silanes for improving hygroscopic properties was determined and compared to their impact on hydrophobicity of the studied materials. It was found that 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane was the only silane improving hydrophobic and hygroscopic properties. The analysis of the applied models of sorption isotherms depicted that the GAB model was not valid for describing water sorption isotherms in the case of the tested materials, while the GDW and Y-B models provided a much more realistic description of water sorption mechanisms. The evaluation of the results of fitting the GDW model indicated that water molecules bonding to the primary sites was the dominating mechanism of sorption.