Poplar Veneer Research Articles

A functionalization approach of decorative poplar veneer accomplished via reactive dyeing followed by in-situ synthesis of ZnO-Ag nanoparticles

Fast-growing wood has been widely used in manufacturing decorative material for wood-based panels. However, the deterioration of the decorative quality of the decorative material is still a hard nut to crack. The single decorative function of this material also makes it challenging to meet the requirements of the current consumer market. In this study, a novel method for the preparation of decorative poplar veneer that integrated multiple functions was proposed. It was accomplished via reactive dyeing of poplar veneer followed by in-situ synthesis of ZnO-Ag nanoparticles (NPs) at room temperature. The critical functional parameters and preparation mechanism of the functional decorative material were systematically analyzed. Results demonstrated that ZnO and Ag NPs were synchronously formed through the in-situ redox of metal ions and subsequent self-assembly in an alkaline medium. The ZnO-Ag NPs were uniformly distributed on the surface of dyed wood. The color change of the prepared decorative material was reduced by at least 40 % due to the physical obstruction of the ZnO-Ag NPs layer. More importantly, the antibacterial, hydrophobic, and flame retardant properties of the prepared material were also synchronously improved. This study provided a new approach to improving the quality of wood-based decorative materials.

A Highly CO2-Sensitive Wood-Based Smart Tag for Strawberry Freshness Monitoring.

Smart tags are used for monitoring the freshness of foods. However, they often lack significant color changes, and their accuracy needs to be improved. In this study, a poplar veneer with a natural pore structure was selected as a matrix to prepare a smart tag with high pH sensitivity for tracking the freshness of strawberries. The delignified veneer was modified using 2,3-epoxypropyltrimethylammonium chloride (EPTAC) to be given positive charges to adsorb bromothymol blue (BTB) through electrostatic interactions. The adsorption capacity of the veneer reached 7.0 mg/g at 50 °C for 4 h, and the veneer showed an obvious blue color. The smart tags exhibited distinct color changes at different pHs and showed quick color changes in response to acetic acid. As the freshness of strawberries decreased, the color of the smart tags changed from blue to yellow-green, which indicated that the accuracy was high. In this study, an effective method was fabricated to prepare a highly sensitive tag, promoting popular application to ensure food quality.

High-performance bamboo-wood composite materials based on the natural structure and original form of bamboo: Fracture behavior and mechanical characterization

Reducing the destruction of bamboo's original structure to produce high-utilization and high-performance engineered bamboo products has long been a goal in the industry. This study developed a new natural arc-shaped laminated bamboo-wood lumber (NALBWL) based on the natural structure and original form of bamboo, using equal arc-shaped bamboo split (EASB) and poplar veneer. A multi-scale analysis of the bending performance and crack propagation dynamics of EASB and NALBWL was conducted. EASB's modulus of elasticity (MOE) and rupture (MOR) were 1.06 and 1.17 times higher than those of air-dried bamboo, respectively, exhibiting excellent mechanical properties. Additionally, its toughness in the full and elastic-plastic stages were 1.24 and 1.38 times higher than those of air-dried bamboo. NALBWL's MOE and MOR were 12.73 GPa and 174.41 MPa, fully meeting structural material requirements and even surpassing most engineered bamboo products. Moreover, NALBWL's radial bending load values were 2.29 and 2.24 times higher than that of EASB and air-dried bamboo, respectively, and it also demonstrated excellent water heat and drying resistance in impregnation and peeling performance. Real-time crack propagation analysis indicated that NALBWL's superior mechanical properties benefited from the respective advantages of bamboo and poplar veneer. This work showcased the application of "natural form-inspired design" in developing bamboo-wood composite materials, and the conclusion provided a reference for the sustainable development of engineered bamboo products and the study of biomass material fracture mechanisms.

A Novel Intumescent MCA-Modified Sodium Silicate/Acrylic Flame-Retardant Coating to Improve the Flame Retardancy of Wood.

The incompatibility between inorganic flame retardants and organic acrylic coatings represents a significant challenge that requires resolution. This work selected environmentally friendly organic aqueous acrylic coatings as the substrate, sodium silicate hydrate as the inorganic flame retardant, and melamine cyanurate (MCA) as the flame-retardant modifier and the flame-retardant co-modifier, with the objective of improving the dispersion and flame-retardant properties of sodium silicate hydrate in the aqueous acrylic coatings. Subsequently, the sodium silicate/MCA/waterborne acrylic acid flame-retardant coating was prepared. The flame-retardant treatment was then applied to poplar veneer in order to create a flame-retardant poplar veneer. The dispersion of the flame-retardant coating was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), and X-ray diffractometry (XRD). Furthermore, the flame-retardant properties of the flame-retardant poplar veneer were analyzed by thermogravimetry (TG), limiting oxygen index (LOI), and cone calorimeter. The results demonstrated that the MCA-modified sodium silicate flame retardant was well dispersed in aqueous acrylic coatings. The results of the flame-retardant properties of the poplar veneer indicated that the ignition time of the 9% flame retardant-treated poplar veneer was increased by 122.7%, the limiting oxygen index value was increased by 43.0%, and the peak heat release rate (pHRR), the peak total heat release rate (pTHR), and the peak mass loss rate were decreased by 19.9%, 10.8%, and 27.2%, respectively, in comparison to the non-flame retardant-treated poplar veneer. Furthermore, the residual char mass increased by 14.4%, and the residual char exhibited enhanced thickness, density, and regularity. The results demonstrated that MCA was an effective promoter of sodium silicate dispersion in acrylic coatings. Furthermore, the sodium silicate/MCA/waterborne acrylic flame-retardant coating significantly enhance the flame retardancy of wood, and its flame retardant mechanism was consistent with the synergistic silicone-nitrogen expansion flame-retardant mechanism. This work presents a novel approach to enhancing the dispersion of inorganic flame retardants in organic coatings, offering a valuable contribution to the advancement of research and application in the domains of innovative flame retardant coatings and flame retardant wood.

A delignified longitudinal-cutting poplar veneer-based epoxy resin composite with excellent transmittance, haze, flexibility and wood fiber art texture

A delignified longitudinal-cutting poplar veneer-based epoxy resin composite (TLPE) with excellent transmittance, haze, flexibility and wood fiber art texture, that was prepared by delignifing longitudinal-cutting poplar veneer (LPV) and filling the delignified LPV with epoxy resin (ER). The TLPE has retained the porous structure and wood fiber art texture of LPV due to the fact that it is not completely filled with resin. The changed benzene skeleton and the ether (C-O-C) were found in the TLPE, that should be due to the chemical combination between the benzene of filled ER and the cellulose of delignified LPV, and the chemical reaction between the benzene and the cellulose yielded the C-O-C. Parts of the TLPE that are completely filled with the ER, that can reach a transmittance of approximately 90 % and a haze of approximately 90 %. Moreover, due to the combined action between the fibril of delignified LPV and the ER, the TLPE has high refractive index fluctuation in the perpendicular direction of fiber and excellent flexibility (the elongation at break: 15 %). When the TLPE is used as the building material, the TLPE can provide a comfortable lighting effect after the light passes through it, it can also accommodate various streamlined and natural artistic shapes with wood fiber art texture in buildings, and it can also achieve a balance between science and art in the building through its optical, styling, and textural advantages.

The Effect of Type of Reinforcement, Type of Glue and Reinforcement Place on Mechanical and Physical Properties of LVL

This study investigated the effect of the reinforcement type, glue type, and reinforcement placement on the mechanical and physical properties of LVL. In the study, the glues used were phenol- formaldehyde (FF), epoxy (EX), and polyurethane (PU), while reinforcement materials used were glass fiber, basalt, jute, and cotton fabric. The following three reinforcement combinations were applied: the first was on the bottom surface, the second was on the first adhesive line at the bottom, and the third was on both the bottom and the first adhesive line at the bottom. As part of the study, researchers manufactured 9-layer laminated veneer lumber (LVL) using alder veneers for the surface, and poplar veneers for the middle layers. They produced a total of 39 different combinations of LVL. The mechanical and physical properties of the produced samples were determined. According to the test results, bending strength (BS), modulus of elasticity (MOE), oven-dry specific gravity, and equilibrium moisture content of samples were higher with FF than with other glues. While the samples with EX glue provided the lowest values in water absorption and thickness swelling tests, glass fiber-reinforced samples provided the highest mechanical values. In addition, the samples having reinforcement on the bottom surface provided higher BS and MOE values.

Influence of micron-sized oligomeric semisiloxane modification on surface properties of veneer and interfacial adhesion of EVA film/poplar plywood

ABSTRACT Using EVA film as an adhesive to composite with wood veneer can fabricate e formaldehyde-free wood-based panels. In order to improve the interfacial adhesion of the thermoplastic resin plywood, micron-sized oligomeric semisiloxane (MS) solution was prepared and sprayed on the poplar veneer before bonded with the EVA film. The effect of MS solution on the surface properties of poplar and mechanical properties of MS-treated plywood by FTIR, XPS, WCA, and SEM-EDS. The results indicated that MS was successfully grafted onto the surface of veneer by covalent bonding (Si-O-C) and formed a rough hydrophobic coating on the veneer. The WCA of poplar veneer was significantly increased. As a result of the change in surface properties, poplar veneer formed a tight interfacial bonds with EVA film, which improved mechanical performance of plywood. When the MS treatment conditions were 3% silane, 15% neutral silica, and 3 h reaction times, the wet shear tensile strength and dry shear tensile strength reached 1.03 and 1.56 MPa, respectively. Compared with untreated plywood, the wet strength and dry strength were increased by 76% and 39%, respectively. In addition, Reduced gaps between MS-treated poplar veneer and EVA film and formed stronger interlock structures were observed by SEM.

Developing poplar wood into a green structure-decoration integrated material for prefabricated wooden building application

Fast growing poplar wood poses significant challenges including low mechanical strength, poor dimensional stability and weak texture, limiting its direct application in the field of building structures and decoration. We treated poplar wood using compression, digital printing and waterproofing techniques to develop a green structure-decoration integrated material. The compression treatment significantly improved the wood density, fiber orientation and surface smoothness. At a compression ratio of 60 %, poplar veneer demonstrates remarkable improvements in modulus of elasticity (MOE), modulus of rupture (MOR) and surface smoothness, with increases of 222.53 %, 233.53 % and 93.20 %, respectively, compared to uncompressed wood. Notably, this compression treatment reduces the surface roughness of poplar to 0.75 μm, meeting the flatness requirements for digital printing. Consequently, clear textures and vibrant colors are directly printed onto the flat surface of compression-densified poplar wood, eliminating the need for traditional surface sanding pre-treatment process, and accordingly improving the efficiency of the material preparation. Furthermore, a final waterproofing emulsion spraying treatment creates a dense micro/nanoscale hierarchical structure on the surface, enabling the compression-densified poplar wood samples to achieve MOE and MOR of 14.15 GPa and 123.00 MPa respectively, even after water absorption and re-dried processes. These values consistently exceed the standard value of MOE (12.50 GPa) and MOR (35.00 MPa) for the highest grade (TCT40) specified in GB50005-2017, indicating significantly improved structural stability. The structure-decoration integrated materials developed in this study offer high strength and dimensional stability, making them promising candidates for high value utilization in prefabricated wooden buildings.

Properties of poplar veneer modified by Acid Red 3R dye in combination with ammonium dihydrogen phosphate

Ammonium dihydrogen phosphate (ADP) is a nitrogen-phosphorus-based inorganic flame retardant that is environmentally friendly and non-toxic. Wood treated with ADP has enhanced thermal stability and flame retardancy. Compounding ADP with Acid Red 3R dye further improves the decorative effect of the wood on the basis of excellent flame retardancy, resulting in a kind of dyeing and flame retardant multifunctionalized wood. Single-factor tests were designed to investigate the effects of flame retardant concentration, dye concentration, temperature, and time on three evaluation indexes: dye-uptake, color difference, and oxygen index, respectively. Through SEM and FTIR analysis, it was found that after the wood was simultaneously treated with flame retardant and dye, the two additives were aggregated in the grain pores of the cell wall by a simple physical combination. They did not undergo a chemical reaction. TG analysis showed that fire-retardant dyed wood had good thermal stability, which can delay the thermal degradation of wood and increase the residual charcoal rate of wood. XRD showed that the crystallinity of fire-retardant dyed wood increased compared to untreated wood. Through cone calorimetric test, it is found that flame retardant dyed veneer had excellent flame retardancy.

Research on the Preparation of Wood Adhesive Active Fillers from Tannin-/Bentonite-Modified Corn Cob

The artificial plywood industry in our country relies heavily on industrial flour as a filler for adhesives. Using abundant corn cob powder as the main raw material, corn cob powder was modified by impregnation with a sodium-based bentonite/bayberry tannin and used as filler for urea–formaldehyde resin (UF) adhesive, with NH4Cl as the curing agent and poplar veneer as the raw material to prepare plywood. The results showed that the modified corn cob powder with a particle size of 250 mesh was uniformly dispersed in the UF adhesive. When used as a filler, the modified corn cob powder effectively prevented the premature curing of the UF adhesive and significantly reduced its viscosity. Compared with flour filler, the bonding strength of the prepared plywood increased by 12.1%–19.6% while the formaldehyde emission decreased by 12.7%–27.8%. The cold pressing performance of the plywoods prepared with modified corn cob flour was comparable to the performance of plywood produced with industrial flour.

Sodium Silicate/Urea/Melamine Ternary Synergistic Waterborne Acrylic Acid Flame-Retardant Coating and Its Flame-Retardant Mechanism.

Waterborne acrylic coatings, the largest market share of predominant environmentally friendly coatings, face limitations in their extensive application due to their flammability. The flame-retardant properties of the coatings could be significantly enhanced by incorporate inorganic flame retardants. However, inorganic flame retardants tend to aggregate and unevenly disperse in waterborne acrylic coatings, causing a substantial decrease in flame retardancy. In this work, sodium silicate was utilized as a flame retardant, with urea and melamine serving as modifiers and synergistic agents. This combination resulted in the preparation of a sodium silicate/urea/melamine ternary synergistic waterborne acrylic flame-retardant coating. This coating was applied to the surface of poplar veneer to create flame-retardant poplar veneer. Subsequently, various instruments, including a scanning electron microscope (SEM), a limiting oxygen index meter (LOI), a thermogravimetric analyzer (TG), and a cone calorimeter (CONE), were employed to investigate the relevant properties and mechanisms of both the flame-retardant coating and poplar veneer. The results demonstrated that the sodium silicate/urea/melamine ternary synergistic flame retardant did not exhibit aggregation and could be uniformly dispersed in waterborne acrylic coatings. The physical and mechanical properties of the ternary synergistic flame-retardant poplar veneer coating were satisfactory. Melamine and urea, acting as modifiers, not only greatly enhanced the dispersibility of sodium silicate in waterborne acrylic coatings, but also assisted in the formation of a silicon-containing char layer through the generation of nitrogen, achieving ternary synergistic flame retardancy. In conclusion, this work explores a novel method to efficiently and uniformly disperse inorganic flame retardants in organic coatings. It significantly improves the dispersibility and uniformity of inorganic flame retardants in organic polymers, thereby substantially enhancing the flame-retardant performance of coatings. This work provides a theoretical basis for the research and application of new flame-retardant coatings in the field of chemistry and materials.

Study on the Process Optimization of Peanut Coat Pigment Staining of Poplar Wood

Wood staining is a crucial technique for enhancing the decorative effect of wood. Different mordants and mordant processes can influence the staining effect of wood. In this study, three types of mordants and mordant methods were selected to improve the color difference and colorfastness to the washing of poplar veneer, using green peanut pigment as the dye. An orthogonal test was conducted to investigate the effects of mordant temperature, mordant time, and mordant concentration on color difference and colorfastness to washing. Range and variance analysis were employed to determine these properties’ main factors. A fuzzy comprehensive evaluation method was used to evaluate and optimize the color difference value and colorfastness of washing. The results revealed that all three factors had significant impacts on both color difference and colorfastness to washing during the process of mordant staining. The optimal process conditions (temperature, concentration, time) for achieving desirable staining effects on poplar veneer were determined as 50 °C, 0.8%, and 2 h, respectively. Furthermore, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses demonstrated that the dye formed complexes with poplar wood, enabling it to adhere to wood grain apertures and tube walls effectively. Mordant treatment increased the crystallinity of stained wood significantly while improving its overall staining performance considerably. This study provides substantial data support for future optimization processes involving natural pigment coal staining in wood.

Izrada laminata upotrebom kompozita od drva i otpadne gume

This study aimed to develop laminate flooring composite using a combination of wood and waste tire rubber (WTR). Plywood panels were produced by using beech (Fagus orientalis), alder (Alnus glutinosa), and poplar (Populus) veneers in a 7-ply configuration. To enhance the physical-mechanical properties of the panels, three loadings of nano-SiO2 (0, 2, and 4 wt%) along with 2 wt% of hexamethyldisilazane (HMDS) were added. Commercial urea-formaldehyde (UF) resin and methylene diphenyl diisocyanate (MDI) were used to bind the wood layers and rubber layers together. The mechanical properties, including modulus of rupture (MOR), modulus of elasticity (MOE), impact strength (IS), hardness strength (HS), and physical properties, such as density (D), water uptake (WU), and thickness swelling (TS), were evaluated. The results showed that increasing the WTR content led to improvements in the physical properties (D, WU, and TS), while negatively affecting the mechanical properties (MOR, MOE, IS, and HS) of the resulting panels. However, the addition of nano-SiO2 improved both the physical and mechanical properties (MOR, MOE, and HS) of the panels. Furthermore, it was observed that the mechanical properties were enhanced with increasing the number of beech layers, although the WU of panels decreased compared to panels made with alder and poplar. Overall, the improvement in the physical properties of the panels followed the order of the arrangement of rubber layers > nano-SiO2 content > veneer layers.

Investigation of mycelium film as the adhesive for poplar veneer bonding: insight into interfacial bonding mechanisms

ABSTRACT The emergence of mycelium-bonded biocomposites has been stimulated in the quest for sustainable development. These biocomposites exhibit enhanced mechanical properties through hot pressing, with mycelium playing a crucial role as both the adhesive and reinforcing material in this composite system. This study aims to investigate and compare the effectiveness of different mycelium films for veneer bonding, with a specific focus on the interface between the mycelia and the substrate. Two fungal species, Pycnoporus sanguineus and Trametes versicolor, were utilized to colonize poplar veneers for 14 days. Subsequently, a wood bonding interface was successfully established between the mycelium film and the decayed veneer surface. The results revealed that bonded veneers with the mycelium film of Pycnoporus sanguineus exhibited higher adhesion strength with 1.76 ± 0.16 MPa. A series of analyses have revealed the occurrence of both mechanical and chemical bonds between mycelia and wood. The bonding interface between mycelium and wood was formed by a synergistic combination of mechanical interlocking, hydrogen bonding interaction, Schiff base reaction, and lignin repolymerization. This study provides valuable insights into the underlying mechanisms involved in the formation of interfacial bonding by fungal mycelia.

Developing a water-resistant cellulose-based wood adhesive based on dual dynamic Schiff base and disulfide bonds

Cellulose-based adhesives have been a research focus in the wood composites industry in view of their eco-friendly characteristics with little negative impacts on human health and ecology. Water-resistant property of the adhesives, however, is still a remaining challenge in the wood-based industries to compete with conventional petroleum-based ones. Herein, microcrystalline cellulose (MCC), a natural and renewable biomacromolecule with extensive resource, was selected as matrix material. Firstly, the hydroxyl groups on C2 and C3 in MCC were oxidized to aldehyde groups in the presence of periodate, resulting in the formation of dialdehyde cellulose (DAC). In consideration of the weak water-resistance of DAC, an integrated strategy that combined DAC with cystamine (CA), was proposed, and a water-resistant cellulose-based DAC-CA adhesive was developed through the cross-linking reaction between DAC and CA. Furthermore, in order to make the adhesive adequately exert the function for bonding of poplar veneer, we performed the interfacial treatment on the poplar veneer using sodium periodate. The performance and structural characteristics of the prepared DAC-CA adhesive were systematically and thoroughly investigated using a multi-spectroscopy technique. The results revealed that the wet bond strength of the DAC-CA adhesive for poplar veneer was higher than that of individual DAC, ranging from 0 MPa in DAC to 0.72 MPa in DAC-CA adhesive. This improvement can be attributed to the enhanced cohesion and toughness resulting from the dynamic Schiff base and disulfide bonds present in the DAC-CA adhesive. In addition, after interfacial treatment, the wet bond strength of DAC-CA adhesive for poplar veneer was dramatically improved, increasing from 0.72 MPa without treatment to 1.06 MPa with treatment. Overall, a water-resistant cellulose-based DAC-CA adhesive was prepared by a rapid and efficient method. This study may provide insights into the development and utilization of innovative wood adhesives.

An ultraviolet shielding material based on lignin nanoparticles engineered with deep eutectic solvents for long-term outdoor application

Ultraviolet radiation (UV) has a significant effect on the wood, and the commonly used UV shielding agents are easily degraded. Lignin is a bio-based UV screening agent and tuning of its nanoparticles is meaningful for realizing the UV shielding properties and stability of composites. With the modification of the deep eutectic solvents based on sulfamic acid and urea, lignin nanoparticles with amino functional groups were prepared, and a protective layer with UV shielding properties was constructed on the surface of the poplar veneer. The phenolic hydroxyl groups, carbonyl groups, and conjugated structure of lignin nanoparticles endowed the composites with the properties of UV shielding, photothermal conversion, and photothermal de-icing. The results of this study provide a benchmark for realizing the low-cost and sustainable preparation of wood composites with UV shielding and are conducive to promoting the high-value application of lignin nanoparticles.

The Effect of Press Parameters on the Physical and Mechanical Properties of Cement-Bonded Particleboards Produced from Veneer Wastes

This study aims to investigate the effect of press temperature and time changes on the physical and mechanical properties of cement-bonded particleboards produced using poplar veneer wastes (Populus tremula L.). In this study, single-layer cement-bonded particleboards with a target density of 1200 kg/m3 and a size of 500 x 500 x 10 mm3 were produced using 5 different pressing parameters. The physical (moisture content, density, water absorption, and thickness swelling) and mechanical (modulus of rupture, modulus of elasticity, internal bond strength, and s screw withdrawal strength) properties of the produced boards were investigated. According to the results obtained, the changes in press time and temperature did not cause a significant change in the water absorption values, while the increase in the pressing time affected the thickness swelling values positively. While the mechanical properties increased with the increase of the pressing time, values suitable for the standard were obtained in all board groups. In addition, it was determined that the most suitable time for production was 24 hours and the temperature application did not have a significant effect on the board properties

Preparation and characterization of plywood panels using recycled HDPE as a formaldehyde-free adhesive: A comparative study

Formaldehyde-based resins such as urea-formaldehyde (UF) are the most widely used adhesives in the plywood industry. However, due to the concerns about formaldehyde toxicity, there is a need to develop formaldehyde-free adhesive materials. Therefore, the present study aimed to minimize or eliminate the harmful effects of UF resin by using recycled high-density polyethylene (HDPE) from post-consumed fruit packing boxes as a nontoxic adhesive. Three-layer plywood panels using poplar veneers and recycled HDPE films were prepared. UF was used as a control adhesive for the comparison. The influence of three variable parameters in terms of HDPE content (from 80 to 320 g/m2), hot-pressing temperature (from 140 to 180 °C), and pressing duration (from 3 to 8 min) on the properties of plywood panels were evaluated. For evaluation, physical properties, namely water absorption (WA), thickness swelling (TS), and mechanical properties, namely modulus of elasticity (MOE), modulus of rupture (MOR), and glue-line shear strength of the samples, were studied. The findings of this work confirmed that HDPE films gave the values of mechanical properties of plywood panels comparable to those obtained with UF adhesive, even though the adhesive content and pressing time were lower than when the UF adhesive was used. The obtained bonding strength values of HDPE-bonded plywood panels ranged from 0.82 to 1.60 MPa and met the requirement for the European Standard EN 314-2. According to FE-SEM micrographs, the fractured surface of plywood panels with 240 g/m2 of HDPE displayed a homogeneous cross-section area, and a large amount of HDPE was attached to the veneer surfaces. It was found that the average mechanical properties tended to increase with an increase in the pressing temperature and time. The type of adhesive had a significant effect on WA and TS. The smallest values of WA and TS were observed in plywood samples using high contents of HDPE films (240 and 320 g/m2). The optimum conditions were an HDPE loading of 240 g/m2, a hot-pressing temperature of 160 °C, and a hot-pressing time of 5 min. The overall results showed that recycled HDPE had enough potential to reuse as a promising adhesive for the environmentally-friendly plywood manufacturing.

Wood composites based on in situ modification of poplar veneers by PEG-[Bmim]Cl

Due to the high viscosity of pure [Bmim]Cl, PEG was selected to be co-solvent to form the solvent system. The dissolution and plasticization ability of PEG-[Bmim]Cl to poplar veneer was completed with processes such as hot pressing and coagulation bath to achieve the in-situ modification of poplar veneers to develop an innovative wood composite, which are expected to be molded. At the same time, the effects of the solvent system on the properties of wood composites were studied. The results showed that both the [Bmim]Cl-treated group (B) and the PEG-treated group (C) had a certain degree of plasticity when compared with the untreated group (A). The PEG-[Bmim]Cl-treated group (D) had the greatest ductility. The main reason was that PEG and [Bmim]Cl synergistically in situ dissolve the components of the veneer, increasing the proportion of the matrix phase (dissolved part). The interface bonding between the matrix phase and the reinforced phase was enhanced and resulted in the best comprehensive mechanical properties. However, no other derivative reactions occurred in each group.

A strong soy protein-based adhesive with excellent water retention

Traditional synthetic resin adhesives release harmful substances and can be replaced with more sustainable, eco-friendly, and healthier soy protein-based adhesives. However, the low water retention of these adhesives leads to an unstable bonding performance, which hampers their widespread application. Enhancing the water retention of the adhesive while maintaining its bonding and coating performance poses a significant challenge. In this work, a “bond-stitch” topology was designed and constructed by free radical copolymerization between acrylic acid and zwitterionic sulfobetaine methacrylate. This topology was combined with lithium chloride and a self-made epoxy crosslinking agent to construct a water-retaining and enhancing structure in soy protein adhesive systems, achieving simultaneous improvement in water retention, bonding strength, and coating performance. The adhesive exhibited an average shear strength of 1.77 MPa for wood and 1.82 MPa for stainless steel. Additionally, the coating performance was significantly improved, allowing uniform coating on wet poplar veneers (up to 120% moisture content) and low surface free energy substrates. Importantly, the adhesive allowing over 75% of the mass to remain after 24 h of storage in an open environment. This strong water-retaining and enhancing structure construction strategy offers a promising way to develop bio-based adhesives and hydrogels, promoting their widely application.