European Journal of Wood and Wood Products最新文献

Wildlife bridges represent a major component of any sustainable strategy to counteract the negative consequences of cutting the natural habitat of wildlife into disconnected parts by motorways and rail. This is especially true for a small and densely populated country such as Switzerland with diverse wildlife scattered through its territory. Up to now all wildlife bridges in Switzerland have been made of concrete with steel reinforcement. The wildlife bridge under investigation here is the first one in Switzerland made of wood-based materials. The idea of building a wildlife bridge by using wood-based materials represents besides a challenging technological endeavor also an ecological progress regarding embodied energy. A further advantage which resulted after realizing the construction, was the short interruption time it needed for installation on a motorway in operation. The most urgent question with respect to the wood-based elements is their moisture uptake when subjected to weather conditions. The present paper reports on a long-term monitoring of this wooden wildlife bridge over a period of approximately 2 years. Different kind of sensors, data from a nearby meteorological station, data regarding hourly number of different kind of vehicles passing beneath the wildlife bridge as well as lab measurements have been used to enable a robust and reliable statement on wooden wildlife bridges subjected to Swiss flatland weather conditions.

Round bamboo is easy to be bent at high temperature. However, there’s a dearth research on bending properties of round bamboo in heating state. In order to investigate the optimal bending parameters in thermal treatment of round bamboo, this study assessed the influence of heating temperature, duration, and moisture content on the bending properties of round bamboo by examining the modulus of elasticity (MOE), modulus of rupture (MOR), and displacements. The findings indicated that the temperature of 160 °C could be considered as a priority, as it resulted in a 67.7% decrease in MOE, a 50.8% decrease in MOR, a 134% increase in elastic displacement (D_e), and a 160% increase in plastic displacement (D_p) compared to the control. Heating durations ranging from 5 to 15 min may be suitable for balancing cost and efficiency. Moreover, a moisture content (MC) exceeding 10% was found effectively to enhance the bendability of round bamboo. Specifically, when MC increased from 0 to 45%, the MOE decreased by 85.6%, the MOR decreased by 68.3%, D_p increased by 8.3%, and D_e increased by 110.3%. Based on these results, it can be inferred that round bamboo with MC above 10%, heated at 160 °C for a duration of 5 min to 15 min, can be easily bent.

The aim of the study was to investigate the densification characteristics of raw, milled, and cut-milled pine and poplar shavings and determine the strength parameters of pellets, pastilles, and granules. In producing agglomerates from hard pine shavings compared to plastic poplar shavings, 19% more specific compaction work was required with over 2-times more specific work to push the agglomerate out of the die opening. Pine agglomerates exhibited lower linear expansion than poplar agglomerates, achieving a higher single density. Due to the elevated content of thermoplastic lignin in the wood (30.7 and 18.4%, respectively), pine agglomerates demonstrated superior radial compression strength parameters, including specific deformation energy, maximum tensile stresses at which agglomerates cracked, and the highest modulus of elasticity. Agglomerates made of cut-milled shavings had the highest single density, but their tensile strength was significantly lower than that of agglomerates made from raw shavings. The susceptibility to densification of the shavings during sequentially repeated densification of small doses during pellet production was the highest, resulting in pellets characterised by the smallest linear and radial expansion, as well as the highest single density of 1081 kg·m^–3 and tensile strength among agglomerates. The smallest single density and strength were observed in granules produced with parameters recommended for particleboard production: a temperature of 170 °C and an agglomeration pressure of 12 MPa, compared to 93 °C and 70 MPa for pellets and pastilles, respectively. The higher temperature did not compensate for the much lower pressure. Shavings compaction parameters for granules are not recommended for particleboard production without a binder, typically urea–formaldehyde resin.

The biological resistance of rubberwood (Hevea brasiliensis Muell Arg.) treated with linseed oil and paraffin wax nanoemulsions containing zinc oxide (ZnO) and copper oxide (CuO) nanoparticles against a white-rot (Trametes hirsuta) and a brown-rot (Oligoporos placenta) fungus was investigated. Rubberwood specimens were treated with nano preservative formulations prepared by dispersing nano particles of ZnO and CuO (conc. 0.5–2.0% w/v) and exposed to brown-rot and white-rot fungus following IS-4873:2008 standard. The nanoemulsions containing ZnO and CuO nanoparticles exhibited good resistance to fungal decay, the efficacy of wood treated with CuO nanoparticles dispersed nanoemulsion was better than wood treated with ZnO nanoparticles dispersed nanoemulsion. Scanning electron microscopy and Fourier transform infrared (FTIR) spectroscopic analysis of decayed wood confirmed less degradation in nanoemulsion-treated wood compared to untreated specimens. This study depicts the nanoparticles dispersed wax and oil nanoemulsions as effective wood preservation strategy for enhancing the resistance of wood against wood decaying fungi.

Kraft lignin is generated as a side stream of the kraft pulping process that is normally burnt to produce steam and energy. However, given its high availability as the second most abundant biopolymer, a lignin biorefinery is a promising approach to reach a sustainable bioeconomy. Nevertheless, this is still challenging because of lignin’s complex structure, low reactivity, and heterogeneity. The modification of lignin to produce lignosulfonates is a possible use once they have already been validated by the market as plasticizers in concrete mixtures, surfactants, etc. This work aimed to produce lignosulfonates from commercial eucalypt kraft lignin and heat-treated lignin by a sulfomethylation reaction, analyze their use as a concrete plasticizer, and compare them with a commercial admixture. The produced lignosulfonates presented a higher concentration in sulfur content, as no purification step was employed, but still a significant increase in water solubility from 7.2% to 98.8% when compared to kraft lignin. Cement pastes, as well as fresh and hardened concrete specimens were produced for the evaluation of the plasticizing performance. Moreover, the consistency (slump test) of fresh concrete, the axial compression strength of hardened concrete, and the viscosity of cement pastes were analyzed. In concentrations of around 2.2%, both kraft lignosulfonate and heat-treated lignosulfonate were found to display an increase in concrete workability from 75 to 95%. Therefore, both lignosulfonates were found to be promising since they present the potential to not only reduce water consumption in concrete preparation while maintaining similar resistance, but also improve waste management in kraft mills.

In order to investigate the mechanical behavior of curved glulam structures, five-point bending tests were conducted on three typical glulam structures, i.e., glulam curved beam, arch, and beam string. Different failure modes can be observed in the test results, which changed from brittle tensile failure to ductile compressive failure. A series of three-dimensional finite element models were established and verified to be effective. Theoretical analysis was conducted to illustrate the failure mechanism of different structures. The results indicated that glulam beam string can bring into full play the compressive characteristics of glulam. The bearing capacity of glulam string is 820.47% higher than that of curved glulam beam and 204.14% higher than that of glulam arch.

Phenol-formaldehyde resins can be used for wood modification through an impregnation process and subsequent curing within the wood cell wall. Phenol is gained from non-renewable resources, and its substitution by renewable chemicals has been a research goal. A promising example for renewable phenol substituents are lignin-derived organic chemicals. Phenol-formaldehyde resins with such substitutions have been studied, however, knowledge of their application for wood modification is deficient. While there are attempts to modify pine and beech wood with this method, studies on other wood species are scarce. Considering the increasing use of different wood species in wood industry, determining the influence of the wood species on the modification quality is an important research goal. Therefore, in this study, vacuum-pressure impregnation of five wood species – Scots pine sapwood (Pinus sylvestris), Norway spruce (Picea abies), European beech (Fagus sylvatica), Silver birch (Betula pendula), and European aspen sapwood (Populus tremula) – with phenol-formaldehyde resins is described. Here, up to 45% of the phenol in the synthetic resin is substituted by vacuum low-temperature microwave-assisted pyrolysis cleavage products from commercial softwood kraft lignin. The solution uptake, weight% gain, leaching, and anti-swelling efficiency of the modified wood are analyzed and compared. The results indicate that up to 30% of the phenol can be substituted without significant decreases in the performance of the modification. The method gives comparable results for most of the wood species described herein, with exception of beech wood, for which the modification had a lower quality. The results could help to develop more environmentally friendly wood modification methods for several common European wood species.

Generally, ethanol is the alcohol commonly used in the SO₂-alcohol-water (SAW) fractionation process. In this study, Eldar pine (Pinus eldarica) was fractionated with different alcohols (methanol, isopropanol, and 2-methyl-2-propanol, in comparison to ethanol) at 135 °C, duration (60–120 min.), and liquor composition (SO₂:alcohol:water = 12:44:44, w/w%) to achieve a consistent kappa number (∽25). The field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to analyze the changes in physical and chemical structure characteristics of selected pulps. The use of isopropanol, as opposed to ethanol (common alcohol in SAW fractionation), showed a beneficial effect on the delignification rate. Meanwhile, both methanol and 2-methyl-2-propanol reduced the delignification rate. Moreover, isopropanol pulp required fewer beating revolutions to achieve a similar freeness (∽385 mL CSF) compared to other alcohols. Handsheets produced from isopropanol fractionation exhibited superior characteristics, including air permeability, apparent density, and tensile, tear, and burst indexes, when compared to those obtained from other alcohols. Overall, isopropanol is a highly suitable alternative to ethanol in SAW fractionation.

Gluing wood in the wet state can reduce warping, splitting, and increase processing volume recovery. Adhesive open time and moisture content may play an important role in bond line strength, but there are no specifications for wet wood bonding. Wood specimens at two different moisture contents were glued with three polyurethane adhesives and tested in shear on the bond line. Open time of 15 min was superior to 4 and 40 min. All adhesives performed better when wood was glued at 30% moisture content than at 101%, but only the 15- and 40-min open time met the minimum shear requirement.