Wood-based Composite Materials Research Articles

Evaluation of the Possibility of Using a Wood-Based Composite Material for Layered Formation of Items Considering Thermomechanical Properties

Evaluation of the Possibility of Using a Wood-Based Composite Material for Layered Formation of Items Considering Thermomechanical Properties

Effect of heat treatment on electromagnetic shielding performance of electroless copper-nickel on wood

The wood-based composites have received extensive attention in the field of electromagnetic interference (EMI) due to inherent layered porous structure. In this study, the deposition Ni and Cu-Ni on wood surface and heat treatment temperature were used as variables. The variation law of electromagnetic shielding (EMS) performance of composite materials is analyzed. The results showed that Ni particles were fully filled in the layered porous structure of the wood, and the metal coatings evenly covered the entire wood surface. The Ni content of the wood based composite materials via 260 °C heat treatment was up to 98.04 %. The pore structure was more regular with the increase of the number of deposition Ni. The ideal roughness was 11.33 μm and the conductivity reached a maximum of 46.8 S/cm at 200 °C. The EMS effectiveness of one deposition Ni composite materials showed an increasing trend when the heat treatment was 200 ℃, 220 ℃, 240 ℃, 260 ℃ and 280 ℃, respectively. When the heat treatment temperature is 260 °C, the EMS effectiveness of the wood-based composite material can reach 88.76 dB, and the hydrophobicity can reach 99.55 °. When the temperature is 300 °C, the electromagnetic shielding effectiveness can reach 91 dB, and the hydrophobicity can reach 117 °. The anisotropic internal porous structure of wood matrix and the multi-interface polarization between wood and Cu-Ni are the main reasons for the high EMS performance.

Strong and antistatic biomass adhesive for wood-based composites with electrostatic discharge protection function

Soybean protein adhesive, as an aldehyde-free biomass adhesive, has gained significant attention as an environmentally friendly material in recent years. It not only aligns with the objectives of the double carbon strategy but also contributes to the environmental protection strategy of reducing carbon emissions. And the functional modification of soybean protein adhesive and its wood composite hold great importance in expanding its application domains and meeting specialized requirements. This research focused on developing a robust, antistatic adhesive derived from soy protein as an alternative to formaldehyde-based resins, which represents a critical path in the advancement of wood-based composites that are free from formaldehyde and possess functional properties. However, ensuring the bonding strength of soy protein adhesive while developing antistatic adhesives and their wood-based composite materials is of great research value and challenge. Inspired by the organic-inorganic hybrid structure, this study aimed to prepare a strong and durable soy protein adhesive with excellent mechanical strength and multifunctionality by using a self-synthesized crosslinking agent called AP and the loaded two-dimensional MXene, which was stabilized in a dispersion of nanocellulose (CNC). The dry and wet shear strength of the resulting adhesive increased by 103.8 % and 113.8 % to 2.21 MPa and 1.24 MPa, indicating the stable crosslinking structure formed in adhesive system by the covalent bond between self-synthesized crosslinking agent AP and the carboxyl groups on proteins, as well as the hydrogen bond interactions between C-M and the proteins. Furthermore, the adhesive exhibited significant antistatic and self-extinguishing properties, with the particleboard modified by adhesive SPI/C-M/AP having a resistivity of 9.212 × 1011 Ω cm. The resistivity decreased with increasing MXene content, providing potential applications for places such as school computer rooms and factory electronic equipment rooms. This breakthrough in multifunctional biomass-based adhesives and composite materials enriches the preparation of new types of biomaterials with antistatic and flame retardant properties.

The confinement effect on phase change materials by physicochemical structure of wood-based materials

The impact of the three-dimensional graded porous structure and active functional groups of wood on phase change materials (PCM) is worthy of consideration. It often results in a decrease in the actual latent heat (A) of wood-based composite phase change materials (WCPCM) compared to the theoretical latent heat (T). In this study, natural balsa wood was initially chosen as the encapsulation carrier for paraffin wax (PW) and polyethylene glycol (PEG) to explore the impact of interface effects on PCM. The results demonstrate that the A/T ratio of WCPCM prepared with balsa wood and PW is 0.99, which is higher than that of WCPCM prepared with balsa wood and PEG (0.96) due to the interface confinement effects caused by hydrogen bonding. Subsequently, delignified balsa wood (LW) and hemicellulose-removal balsa wood (HW) were utilized to encapsulate PW, and the spatial confinement effects on PCM were discussed. Delignification resulted in the opening of pits. While hemicellulose removal resulted in the generation of more mesoporous structures in wood. This resulted in a specific surface area of 19.204 m2/g, which is 142.2% larger than that of LW. Both of these changes improved the permeability of balsa wood, leading to an encapsulation efficiency of 88.1% (LW) and 89.6% (HW) for PW, respectively. However, due to the spatial confinement effects of nanoscale pores, the A/T value of HW/PW (HWP) is lower (0.93) than that of PW encapsulated with LW (0.96), ultimately resulting in a lower latent heat for HWP (172.8 J/g) compared to LWP (174.8 J/g). This study provides theoretical insights into selecting PCMs and encapsulation matrices in future research.

Wood-based composite materials in the aspect of structural new generation materials. Recognition research

Wood-based composite materials in the aspect of structural new generation materials. Recognition research

Advisability-Selected Parameters of Woodworking with a CNC Machine as a Tool for Adaptive Control of the Cutting Process

The operation of CNC machining centers, despite their technological progress, can still be affected by undesirable events associated with the technological parameters of their operation. The minimization of these risks can be achieved via their adaptive control in the process of operation. Several input parameters for adaptive control are still the subject of research. The work aimed to find out the influence of the change in feed speed, revolutions, and radial depth of cut on the noise and temperature of the tool during the milling of wood-based composite material particleboard. At the same time, it was evaluated whether it is possible to use the measured values of these parameters in the future in the process of an adaptive control of the CNC machine with the minimization of their negative influence. The methods of measuring these parameters were chosen based on valid legislation and previous research. The results of the research show that all parameters influence both the noise and temperature of the tool, while the rate of the radial depth of cut has the greatest influence on the increase in temperature, and the noise is most affected by the revolutions. The effect of temperature during woodworking can also be characterized in terms of the potential long-term wear of the cutting tool. The setting of optimization algorithms of monitored parameters in the adaptive control of the CNC machining center will be the subject of further research.

High-performance wood scrimber prepared by a roller-pressing impregnation method

Wood scrimber is a wood-based composite material with high mechanical strength and large size, which can potentially replace the use of steel and cement in various fields. However, its poor dimensional stability and low flame retardancy limit its use in outdoor construction projects and fire-prone areas. To solve this, here we report a roller-pressing impregnation method to realize the deep penetration of resin using mechanical compression and low-pressure adsorption. Microstructural imaging by SEM and 3D ultra-deep field microscopy shows the phenol formaldehyde(PF) resin distribution of the roller-pressed wood scrimber (R-WS) is deeper and more uniform, which increases the flatness and crystallinity. The R-WS showed greatly improved dimensional stability, with 63 % and 35 % lower thickness swelling rate (TSR) and width swelling rate (WSR) compared with the traditional wood scrimber (T-WS). In terms of flame retardancy, the smoke production rate (SPR) and heat release rate (HRR) of R-WS decreased by 32.7 % and 52 %, respectively. The R-WS at 800 °C formed a dense char that content increased by 20 %, helping to inhibits combustion. The mechanical properties of R-WS were also improved, and the modulus of rupture (MOR), modulus of elasticity (MOE) and short-beam strength (SS) of R-WS increased by 31.2 %, 7.4 %and 26.7 %, respectively. The R-WS suffer toughness failure and wood-to-wood failure under bending and shear scenarios, respectively, indicating that the roller-pressing impregnation treatment enhanced toughness and bonding strength. In addition, the use of a rotating roller is expected to realize the continuous production of the dipping link, saving drying energy consumption and improving production efficiency. These properties are expected to promote the outdoor utilization and continuous production of wood scrimber.

Low carbon footprint preparation of MXene incorporated lignocellulosic fibers for high thermal conductivity applications

New wood-based composite materials with thermal conductivity are greatly desired in the fields of packaging materials for electronic components. In this study, a new multifunctional composite material (M@FC) is prepared by simply blending clay-like Ti3C2Tx MXene and delignified wood fibers together, and then followed by an infusing epoxy resin with environmentally friendly vacuum assisted resin transfer molding (VARTM) process. The resulting M@FC (0.92 W m−1 K−1) possesses superior thermal conductivity as compared to natural wood (0.099 W m−1 K−1) and most polymers. Furthermore, after the VARTM process, the structure of the M@FC is tighter, and thus showing excellent mechanical properties (tensile strength of 93.0 MPa and flexural strength of 172.7 MPa). In addition, good water resistance and excellent flame retardant property are observed for M@FC. The improvement of thermal conductivity provides the possibility for its application for packaging materials in electronic components. This study using waste wood as the important component provides a new idea for carbon cycling and recycling of natural resources.

Boosting the photothermal conversion efficiency of MXene film by porous wood for Light-driven soft actuators

Ti3C2Tx (a typical MXene) has been widely used in light-driven actuators due to its outstanding photothermal conversion capability. However, the response speed of these actuators is always slow because the effective irradiated area is limited to their surface. Herein, we propose a wood-based composite material which is made by coating Ti3C2Tx on delignified wood (DW). The high porosity of DW leads to high loading of Ti3C2Tx and provides large irradiated areas, thus enhancing photothermal conversion efficiency. The delignification on wood can expose cellulose with highly hydrophilic surface for rapid diffusion of Ti3C2Tx suspension, and the hydroxy in cellulose can act as binding sites to form stable combination with Ti3C2Tx. Taking advantage of the good compressibility of DW, a simple densification is conducted on TDW (Ti3C2Tx/DW) to greatly shorten the distance between adjacent oxygen-enriched Ti3C2Tx nanosheets, enhancing the conjugation among nanosheets, thus endowing TDW with good flexibility and high heat transfer efficiency. Moreover, we manufacture a light-driven bilayer actuator comprised of TDW as the passive layer and low-density polyethylene (LDPE) as the active layer. Our light-driven actuator exhibits a tremendous angle variation of 160° at a light intensity of 120 mW/cm2. A series of devices based on the TDW/LDPE actuator are demonstrated, including simulated gestures, a four-finger soft gripper, and a bionic flower. Moreover, we propose a light-controlled smart switch which can be used on non-contact (COVID-19) or dangerous (blasting) occasions. Additionally, we present a finite element simulation to predict the bending deformation, which guides the accurate control of the devices.

Understanding the PLA–Wood Adhesion Interface for the Development of PLA-Bonded Softwood Laminates

With polylactic acid (PLA) usage projected to increase in wood-based composite materials, a study comparing composite processing parameters with resulting PLA−wood adhesion and panel performance is warranted. In this study, PLA-softwood veneer laminates have been prepared and spatial chemical imaging via FTIR analysis was applied to identify PLA bondlines characterizing bondline thickness and the extent of PLA migration into the wood matrix. These PLA–wood adhesion interface characteristics have been compared with the performance of panels varying in pressing temperature, pressing time and PLA grades. For amorphous PLA, bondline thicknesses (60–120 μm) were similar, pressing at 140 °C or 160 °C, whereas with semi-crystalline PLA, the bondline thickness (340 μm) significantly reduced (155–240 μm) only when internal panel temperatures exceeded 140 °C during pressing. Internal temperatures also impacted PLA penetration, with greater PLA migration from bondlines evident with higher pressing temperatures and times with distinctions between PLA grades and bondline position. Performance testing revealed thinner PLA bondlines were associated with greater dry strength for both PLA grades. Cold-water soaking revealed laminated panels exhibit a range of wet-strength performance related to panel-pressing regimes with the semi-crystalline PLA pressed at 180 °C having similar tensile strength in dry and wet states. Moreover, an excellent correlation between wet-strength performance and bondline thickness and penetration values was evident for this PLA grade. Overall, study findings demonstrate PLA wood composite performance can be tuned through a combination of the PLA grade and the pressing regime employed.

Preparation of transparent wood containing carbon dots for application in the field of white-LED

In this study, the biomass carbon dots (CQDs) with blue and yellow fluorescent colors was prepared by citric acid and urea, and two complementary fluorescent molecules, blue and yellow, were used as the donor-acceptor composite system of white fluorescent emission. Transparent wood-based composites which can emit white fluorescence under the excitation of near ultraviolet light were obtained by encapsulating blue and yellow carbon dots in transparent wood. There is no excessive energy transfer between the donor and the acceptor in this material, and the fluorescence intensity can still be kept at 87.7% or above after 7 days of ultraviolet irradiation, and this material has high mechanical strength and good flexibility. These conclusions confirm that the quantum dot/transparent wood-based composite material prepared in this experiment is a promising encapsulating material for white-light emitting diode (W-LED), which has potential application value in the fields of lighting, monitor, intelligent devices and so on.

Fire Behaviour of Treated Insulation Fibreboards and Predictions of its Future Development Based on Natural Aging Simulation

Wood-based composite materials represent a major fire safety risk. The application of water-based fire retardants (FR) can improve their fire performance. However, it is important to investigate the performance and stability of this protective system over time, as the ageing of materials and their exposure to climatic conditions can change their properties. The aim of this research work was to evaluate the effect of long-term aging on the combustibility of low-density insulation fibreboards (IFs) treated with a water-soluble flame retardant (FR) based on inorganic salts. Both natural and accelerated aging simulations were conducted. The accelerated aging simulation was performed using climate chambers. The FR efficiency was evaluated by the mass loss rate of the tested specimen. As expected, the FR formulation used significantly enhanced the fire properties of the boards, reaching maximum efficiency 6 months after its application onto the fibreboards. Markedly, after 4 years the efficiency of the investigated FR additive was considerably decreased with weight loss values comparable with the values of the untreated samples. Markedly, besides the apparent protection of wood fibers, the retardant did not prevent the gradual increase in mass loss rate of samples, it just slowed down the process. The main result of the study is to determine the effectiveness of the investigated FR on IFs during their natural ageing. The development of accurate datasets on the thermal behaviour of IFs is critical for their proper utilisation in building and construction applications.

Chemical Imaging of the Polylactic Acid − Wood Adhesion Interface of Bonded Veneer Products

The increasing use and potential of polylactic acid (PLA) in wood-based composite materials due to its greater performance over common polyolefins provides the justification for a closer examination of the PLA−wood adhesion performance. In PLA-bonded laminates and composites, the optical differentiation between PLA polymer and wood is not possible and necessitates complex techniques such as fluorescence microscopy to characterize the PLA adhesion interface. In this study, spatial chemical imaging via FTIR analysis has been successfully applied to directly identify PLA bondlines within PLA-bonded veneer laminates and to determine the migration of semi-crystalline and amorphous PLAs from the bondline into the wood structure. This method uses involved point contouring line spectra over the bondline area to distinguish the PLA polymer from the wood. From this quantitative analysis, it is revealed that bondline thickness and PLA penetration values depend on pressing temperature, and this has implications for the reinforcement of the adhesion interface and the bondline performance. Furthermore, in developing a methodology for this assessment, this spatial chemical imaging approach can equally be applied to other polyester, amide, and urethane systems used to bond wood laminates.

Wood-based composite materials for ultralight lens antennas in 6G systems

Example of square and lens shaped samples made of nanocellulose-glass composite (WNF–HGMS) for 6G antennas. Scale bar: 1 cm.

Fire Behavior of Wood-Based Composite Materials.

Wood-based composites such as wood plastic composites (WPC) are emerging as a sustainable and excellent performance materials consisting of wood reinforced with polymer matrix with a variety of applications in construction industries. In this context, wood-based composite materials used in construction industries have witnessed a vigorous growth, leading to a great production activity. However, the main setbacks are their high flammability during fires. To address this issue, flame retardants are utilized to improve the performance of fire properties as well as the flame retardancy of WPC material. In this review, flame retardants employed during manufacturing process with their mechanical properties designed to achieve an enhanced flame retardancy were examined. The addition of flame retardants and manufacturing techniques applied were found to be an optimum condition to improve fire resistance and mechanical properties. The review focuses on the manufacturing techniques, applications, mechanical properties and flammability studies of wood fiber/flour polymer/plastics composites materials. Various flame retardant of WPCs and summary of future prospects were also highlighted.

A tough, anti-mildew and anti-counterfeiting soybean protein adhesive enhanced by gecko-inspired functional fiber and bio-based epoxide

The development of efficient and sustainable formaldehyde-free adhesives has become an important strategy to solve the problems of environmental pollution, resource depletion and clean production. It is a promising and challenging task to prepare multifunctional adhesives with high adhesive strength from soybean protein (SP), an abundant and sustainable biomaterial that is largely produced from agricultural waste. Inspired by gecko toe, carboxylated paper fiber (CPF) anchored by MOFs (namely UiO66-NH2@CPF) was constructed as micro-nano structure reinforcing phase, and resveratrol-based epoxide (RE) was employed as crosslinking agent to formulate a series of SP-based green adhesives. In particular, plywood bonded with SP/RE13/UiO66-NH2@CPF1.5 presented the maximum dry/wet shear strength to 2.52 MPa and 1.43 MPa, which increased by 90.9% and 457% compared to that of adhesive made with SP alone, respectively. SP/RE13/UiO66-NH2@CPF1.5 displayed a 92.02% residual rate (in water at 60 °C for 6 h), showing excellent bonding strength and water resistance. More importantly, SP/RE13/UiO66-NH2@CPF1.5 successfully inhibited the invasion of mold, enabling to extend its shelf time to 12 h. In addition, it showed excellent fluorescent properties, exposing great potential in anti-counterfeiting of wood-based composite materials and information transmission. The development of SP-based adhesives improved the added value of industrial by-products, which not only met the demand for green and sustainable development, but also contributed to clean production by providing environmental and economic benefits along with excellent performance.

Fluorescent thermochromic wood-based composite phase change materials based on aggregation-induced emission carbon dots for visual solar-thermal energy conversion and storage

Efficient solar-thermal energy conversion and storage is significant to overcome current energy shortage problems. Monitoring solar-thermal energy storage process by an evident and convenient display is conducive to improving energy utilization. Herein, fluorescent thermochromic wood-based composite phase change materials (WPCMs) were constructed for visual solar-thermal energy conversion and storage. It was fabricated by encapsulating polyethylene glycol (PEG) and aggregation-induced emission carbon dots (AIE-CDs) showing blue dispersed emission and red aggregation-induced emission into delignified wood (DW). The DW well-preserved the distinctive anisotropic porous structure and prevented the leakage problem of PEG. The WPCMs possessed great solar-thermal conversion capacity benefitting from strong and broad solar light absorption behaviors of AIE-CDs. Additionally, WPCMs showed real-time and visual fluorescent thermochromic property, it exhibited red AIE, and the fluorescence (FL) decreased and shifted into the blue emission band under solar radiation. The solar-thermal energy conversion and storage led to solid–liquid transformation of WPCMs, which promoted AIE-CDs’ dispersion, thereby changing the FL. It also exhibited a high latent heat of fusion (160.8 J·g−1), favorable stability over 150 heating–cooling cycles, thermal stability below 210 °C and good shape stability. The WPCMs can be extended to applications in energy-saving buildings and optical lighting materials with visual thermal regulation capability.

Evaluation of the Influence of the Conditions of Catalytic Continuous Steam Explosive Activation of Wood on the Physical and Operational Properties of Wooded Composite Materials Based on Activated Fibers

This article presents the results of studies of obtaining wood composite board materials without binders using the method of preliminary steam explosive treatment, as well as an assessment of the impact of impregnation conditions and continuous steam explosive activation of wood on the physical and operational properties of wood-based composite materials based on activated fibers. The rational operating parameters for obtaining board wood-composite materials (WCM) have been determined. We established the influence of impregnation modes (temperature, catalyst concentration), continuous steam explosive treatment with afterwash (temperature, pressure, intensity of mechanical action), as well as the properties of activated lignocellulose fibers (composition and morphological structure) on the operational properties of WCM. The expediency of introducing a catalyst (sodium bisulfite) at the washing stage has been proved, since the introduction of sodium bisulfite during impregnation before steam explosive treatment promotes the formation of lignosulfonates in the activated material, which participate in the formation of the physical properties of WCM.

Analysis of Rotational Stiffness of the Timber Frame Connection

Initially, timber was considered only as an easily accessible and processable material in nature; however, its excellent properties have since become better understood. During the discovery of new building materials and thanks to new technological development processes, industrial processing technologies and gradually drastically decreasing forest areas, wood has become an increasingly neglected material. Load-bearing structures are made mostly of reinforced concrete or steel elements. However, ecological changes, the obvious problems associated with environmental pollution and climate change, are drawing increasing attention to the importance of environmental awareness. These factors are attracting increased attention to wood as a building material. The increased demand for timber as a building material offers the possibility of improving its mechanical and physical properties, and so new wood-based composite materials or new joints of timber structures are being developed to ensure a better load capacity and stiffness of the structure. Therefore, this article deals with the improvement of the frame connection of the timber frame column and a diaphragm beam using mechanical fasteners. In common practice, bolts or a combination of bolts and pins are used for this type of connection. The subject of the research and its motivation was to replace these commonly used fasteners with more modern ones to shorten and simplify the assembly time and to improve the load capacity and rigidity of this type of frame connection.

Microstructure and Hydrophobic Properties of Nano-Cu-Coated Wood-Based Composites by Ultrasonic Pretreatment

The combination of nano-metal and wood to prepare copper-coated wood-based composite materials has important research value and practical significance for improving the function of wood, expanding the application field of wood, and adding added value. In this paper, 31-year-old wood (Pinus sylvestris L. var. mongholica Litv) veneer was taken as the research object. The wood veneer was pretreated by ultrasonic wave, and copper film was deposited on the surface of the wood veneer by magnetron sputtering to prepare “environmentally friendly” copper-plated wood-based composite materials. The microstructure and hydrophobic properties of Cu-coated wood-based composites were characterized and studied. With the increase in coating time, the diffraction peak intensity of wood cellulose gradually decreased, and the diffraction peaks of Cu (111), Cu (200), and Cu (220) of metallic copper appeared. Under the sputtering condition of a substrate temperature of 200 °C, the copper film deposit on the surface of the wood was uniform and densely arranged. The surface water contact angle reached 149.9°. Ultrasonic treatment increases the porous structure of wood, and the rough metal copper film interface was constructed on the surface of wood by magnetron sputtering to transform the surface wettability of the wood from hydrophilic to super-hydrophobic. The lotus leaf effect was realized on the wood surface.