European Journal of Wood and Wood Products最新文献

This review paper discusses the potential of laminated strand lumber (LSL) as a structural and building material, with a focus on Hungarian hardwoods such as Turkey oak, hornbeam, beech, and domestic poplar. LSL is an engineered wood product made from thin strands of wood that are glued together in layers. The study compares the physical and mechanical properties of LSL made from these hardwood species with those of other conventional structural materials. In addition, the paper discusses various aspects of LSL such as thermal, morphological, and durability, to provide a comprehensive analysis of the LSL material. Furthermore, a SWOT (strengths, weaknesses, opportunities, and threats) analysis is conducted to understand the strengths and weaknesses of LSL products. This analysis sheds light on the pros and cons of utilizing LSL crafted from certain hardwoods and provides suggestions for improving their performance in various settings. Overall, the report demonstrates the potential of utilizing LSL made from these particular hardwood species and offers recommendations for future studies to benefit LSL manufacturers and researchers significantly.

Drilling resistance (DR) measurements constitute a common method to evaluate the properties and internal conditions of wood. Generally, DR is used to monitor and assess the structural health of timber constructions. This study aimed at evaluating the influence of 3-mm holes left after drilling resistance measurements on the residual failure load of the wood specimens tested under the bending and compression conditions. Laboratory tests were performed using defect-free conditioned specimens of Scots pine (Pinus sylvestris L.) with various cross-sections. Drilling holes were made with an IML-RESI PD 400 tool and a new standard spade drill bit (IML System GmbH, Wiesloch, Germany) in different locations of the cross-section. We used a finite element modelling software to simulate the bending of drilled specimens and assess the accuracy of experimental data. For wood assessment, an orthotropic body model was used with regard to the non-linearity of the load deflection curve. The failure load in static bending was significantly influenced by the presence and location of holes in the specimens. However, this effect varied across the different cross-sections. It is recommended to use DR for the evaluation of structural timber in the areas of wood elements that are not exposed to the maximum tensile stresses. The influence of holes after DR measurements on residual failure load in compression was proportional to the wood cross-section loss and is minor for structural-sized wood constructions.

The frequency of Terahertz (THz) band is between microwave and infrared radiation. THz technology is widely used in non-contact nondestructive testing, material evaluation, security anti-terrorism, medical imaging and diagnosis, communications and other fields. Similarly, THz technology has been widely used in forestry. This paper analyzes the application progress of THz technology in forestry based on the research and application achievements of THz technology in recent years, such as tree species recognition, non-destructive detection of hidden defects in wood, wood moisture content measurement, wood density, some other important application areas (such as dendrochronology, crystalline structure, fiber structure) and summarizes the existing limitations and shortcomings. On this basis, the future application prospect and development trend of THz spectroscopy and imaging technology in forestry are projected. It is expected that this paper can play a positive role in promoting the application of THz technology in forestry, and provide new solutions and methods to solve the technical problems related to forestry.

Resin canals and ray cells in pine wood connect the interior to the exterior. The blockage of resin canals and ray cells by the resin, directly determines the water uptake of the wood. However, research on water uptake by resinous wood is lacking. Hence, this study aimed to explain how microwave (MW) or superheated steam (SS) treatment improves wood water uptake from the perspective of resin content (RC). Therefore, radiata pine sapwood and heartwood were treated with MW, SS, or microwave-superheated steam (MS) for different times. The results showed that MW and SS treatments expelled the internal resin of radiata pine. Owing to the low RC and high moisture content (MC) of sapwood, the effect of the MW treatment on the RC of radiata sapwood was insignificant. Heartwood has a markedly higher RC and lower MC than sapwood; therefore, MW treatment can drive part of the resin to migrate out of the wood. With increasing SS treatment time, the RC of the sapwood and heartwood decreased to varying degrees; however, the core layer resin could not be completely removed. In addition, MW treatment can accelerate the degreasing process as it discharges some part of the resin and opens some parts of the resin canals. Moreover, MS treatment can increase the porosity of sapwood and heartwood due to the expulsion of resin. MS treatment had no significant effect on sapwood water uptake; however, it increased that of heartwood by more than three times. The dye solution enters the wood through the open resin canals or ray cells and communicates with the axial resin canals. Therefore, the water uptake of heartwood is mainly related to the resin content and the blockage of the resin canals by the resin determines the entry of the dye solution to the interior of the wood.

To overcome the defects of longer curing times and higher curing temperatures for melamine urea formaldehyde resins (MUF) used in wood panel products, nanofluid MUF resin adhesives were prepared by dispersing SiO₂ and TiO₂ nanoparticles into the MUF resin at six concentration levels based on the overall mass of the adhesive, 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1%, with the assistance of ultrasound. The excellent thermal conductivities of the nanofluid adhesives eliminated the defects of the MUF resins. When the SiO₂ and TiO₂ nanoparticles were incorporated, the viscosity increased as the nanoparticle concentration increased, the maximum viscosity increased by 13.4% with SiO₂ nanoparticles (1.0% level) and 11.4% with TiO₂ nanoparticles (1.0% level), the pot life, curing time, and free formaldehyde content of the MUF resins declined to varying degrees as the nanoparticle loading level was increased, the pot life maximum decreased by 38.5% with SiO₂ nanoparticles (0.2% level) and 36.0% with TiO₂ nanoparticles (0.2% level), the maximum reduction in curing time was 13.3% with SiO₂ nanoparticles (0.4% level) and 13.6% with TiO₂ nanoparticles (0.6% level), and the maximum content of free formaldehyde was reduced by 32.3% with SiO₂ nanoparticles (1.0% level) and 41.9% with TiO₂ nanoparticles (1.0% level). The nanofluid MUF resins showed much higher bonding strengths and lower formaldehyde emissions than pure MUF resins after being treated with the same hot pressing method used during plywood manufacturing. The maximum bonding strength was increased by 28.8% with the SiO₂ nanoparticles (1.0% level) and 25.4% with the TiO₂ nanoparticles (1.0% level) at a hot-pressing temperature of 100 °C and a hot-pressing time of 60 s/mm. The maximum formaldehyde emissions were reduced by 46.3% with the SiO₂ nanoparticles (1.0% level) and 46.3% with the TiO₂ nanoparticles (1.0% level) at a hot-pressing temperature of 110 °C and a hot-pressing time of 40 s/mm. Furthermore, nanofluid MUF resins used in plywood manufacturing decreased the hot-pressing temperature or shortened the hot-pressing time required.

Black liquor, a major by-product of the paper industry, is often underestimated in terms of its industrial value. Effective utilization of black liquor has become a pressing concern. In this study, electrode materials were prepared using activated carbon derived from black liquor and the optimal conditions for the preparation of black liquor activated carbon with high electrochemical performance was determined. The electrochemical performance of activated carbons obtained through the processes of evaporation and concentration of black liquor, extraction of lignin from black liquor, and direct utilization of industrial lignin, were compared. The results revealed that the optimal conditions for preparing activated carbon were a carbonization temperature of 500 °C and an activation temperature of 700 °C. The specific capacitance was measured to be 389 F/g at 0.5 A/g, with capacitance retention of 100%. Moreover, even after 5000 charge/discharge cycles at a current density of 2.0 A/g, the energy density reached 22.2 Wh/kg. The specific surface area of the activated carbon was determined to be 2147.77 m²/g. One notable advantage of the activated carbon prepared by evaporating the black liquor is that it retained hetero-atoms such as S present in the black liquor. This feature resulted in a higher capacitance compared to other preparation methods.

This paper describes the development and characterisation of wood-filled polylactic acid (PLA) composite filaments for application in fused filament fabrication three-dimensional (3D) printing. Four different wood-polymer composite filaments for 3D printing were prepared, and specimens were 3D-printed with the obtained materials. The composite filaments consisted of wood particles (10% or 20% mass ratio) and a PLA polymer matrix. Wood particles were prepared by grinding and sieving non-modified beech wood and thermally modified (TM) (at 200 °C) beech wood. Thermal modification of wood affected particle preparation and smaller particles with lower aspect ratios were obtained. Filaments with TM wood particles were extruded better than with non-modified wood particles, with lower surface roughness and lower porosity. With a higher wood ratio, the surface roughness and porosity of the filament increased. Non-homogenous filaments also affected extrusion in 3D printing and reduced the properties of 3D-printed parts. Parts 3D-printed from filaments with TM particles had better tensile strength than from filaments with non-modified particles, but were lower than from pure PLA filaments. The tensile strength of the injection-moulded specimens was 18–69% higher than that of the 3D-printed specimens, depending on the filament composition. The results indicate some positive effects of thermal modification of wood particles on the properties of filaments and 3D-printed parts. Nevertheless, further optimisation of particle preparation and extrusion parameters is needed to obtain quality filaments with this size of wood particles.