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Exploring the reusability of wood-based panels is imperative in the wood industry for sustainable development and carbon balance. Non-reusable adhesives make wood-based panel recycling difficult. In this study, inspired by the adhesion and de-adhesion behavior of snail slime, we built dynamic covalent/hydrogen hybrid networks into adhesive system for achieving both high bonding performance and reusability. Specifically, the softwood lignin was purified and pretreated by ultrasonication to form a catechol structure (UAL) and then combined with soybean protein to develop a 100 % bio-based wood adhesive. The catechol structure of UAL formed dynamic covalent bonds (CN) with the amino groups of the protein to improve the water resistance and formed multiple hydrogen bonds as a sacrificial network to improve the toughness of the adhesive. Thus, the wet shear strength of plywood bonded by the resultant adhesive improved by 101.4 % to 1.37 MPa. The adhesive also exhibited flame retardancy (LOI = 37.7 %), mildew resistance (60 h), and antibacterial performance (inhibition zone = 8 mm). Notably, owing to the rearrangement of dynamic covalent/hydrogen hybrid networks and the thermoplastic property of UAL, the resultant adhesive was reusable (3 cycles) and degradable (2 months), which provides a potential method for the reuse of wood-based panels., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Human health and environmental protection demand wood-based panel industry for innovative soy-based adhesives with high production efficiency, straightforward synthesis processes, non-toxicity, and high bonding performance. A simple and efficient microwave pretreatment process and low addition of bio-derived crosslinking agent was used in this study to prepare a non-toxic and high-bonding performance soybean protein-based adhesive. After 4 min of microwave pretreatment time, the complex quaternary structure of soybean protein molecule unfolds, the soybean protein disperses evenly and stably, and active groups of soybean protein molecules are exposed. After adding 3.85% crosslinking agent, the moisture absorption rate of the soybean protein-based adhesive decreases by 41.77%, the residual rate increases by 3.68%, and the wet shear strength of the resultant plywood increases to 1.12 MPa, which satisfies requirement of interior use plywood. Compared with previously reported soy-based adhesives, this adhesive is dependent on fewer chemical reagents, but has good bonding performance. The 204.41% of relative cell viability indicates the resultant adhesive was non-toxic. The proposed high-efficiency, high-performance, non-toxic biomass adhesive has great prospects for the industrial application., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Adhesives are commonly used in the wood industry, such as plywood, fiberboard, and particleboard, for making furniture, flooring, kitchen cabinets, and wall materials. However, almost all of these adhesives come from petroleum resources and release toxic substances that pollute the environment and endanger human health. Therefore, it is necessary to promote the production of eco-friendly adhesives. The development of plant-protein-based adhesives can increase the value of agricultural wastes and reduce the environmental hazards. However, their industrial application is limited by their poor mechanical strength and inferior water resistance. The main purpose of this study was to prepare a green effective reinforcer to improve the water resistance and mechanical strength of soybean meal (SM) adhesive. To achieve the above goals, a natural chelating agent phytic acid (PA)-mediated aminoclay-cellulose nanofiber (AC@CNF) nanohybrid was prepared. Then, the AC@CNF-PA nanohybrids were combined with SM to prepare a high-performance SM-based adhesive. The water resistance of the modified adhesive was remarkably improved, with 105.2 % higher than that of the unmodified SM adhesive in wet shear strength. Moreover, the modified adhesive showed good cytocompatibility, biodegradability, and flame retardancy. This work suggested a new approach in preparing green high-performance protein-based adhesives., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Recently, soy protein has attracted extensive attention from wood industries and consumers in the production of wood adhesives as it is non‐toxic, biodegradable, low cost, and easy to process. There are a variety of reactive groups namely OH, NH2, COOH, and SH, in protein molecules, which offer possibilities for protein denaturation, chemical modification, and increased ionic interactions. The research in protein denaturation, crosslinking modification, biomimetic modification, and organic–inorganic hybrid formulation not only focuses on enhancing the mechanical properties and tolerance to water of the adhesives but also considers its toughness, mildew resistance, and flame retardancy to further optimize the performances of the adhesives. In this paper, soy protein chemical composition, soy protein denaturation, and reinforced modification are discussed to understand these methods and further develop into a multifunctional soy protein‐based adhesive. Given the potential of bio‐based adhesives, these modification methods not only provide the theoretical basis for its development at full scale, but also the possibility for the multifunctional applications of bio‐based adhesives. [ABSTRACT FROM AUTHOR]

Wood adhesives fabricated from biomass can substitute formaldehyde‐based ones, reducing the consumption of fossil resources and eliminating formaldehyde pollution. In this study, a novel and sustainable water‐soluble soybean polysaccharide (WSSPS)‐based adhesive is designed. Specifically, a hyperbranched aminated polysaccharide (HBPA–g–WSSPS), as an adhesive matrix, is synthesized via grafting reaction between oxidized WSSPS and hyperbranched polyamide (HBPA). Triglycidylamine, a bio‐based epoxide cross‐linker, reacted with the HBPA–g–WSSPS to afford a cross‐linked hyperbranched network, providing strong cohesion for the adhesive. Additionally, polyacrylamide imparted an adjustable viscosity to the adhesive. The resultant WSSPS‐based adhesive enhanced the wet shear strength of plywood (1.24 MPa) by 49% compared to the E0‐level industrial‐use melamine‐urea‐formaldehyde (MUF) resin and by 26% compared to the industrial‐use soybean meal/polyamidoamine‐epichlorohydrin (PAE) adhesive. In addition, the adhesive has characteristics similar to those of the MUF resin, including viscosity, coating performance, hot‐pressing conditions, and dry bond strength, which are superior to those of the soybean meal/PAE adhesive. This developed polysaccharide‐based adhesive can potentially enhance various composites and can be used in industrial sectors. [ABSTRACT FROM AUTHOR]

Urea formaldehyde, phenolic, and melamine formaldehyde resins are currently the most common wood adhesives. However, these modern wood adhesives have toxicity problems and most of the raw materials come from non-renewable resources. Ideally, future alternative adhesives will be prepared from non-toxic, inexpensive, and renewable natural materials. We found that borate chemistry can crosslink soy protein (SP) and soy polysaccharides (SPSs) to produce a strong adhesive, which is the core of the stable structure in higher plants. Hyperbranched polyester (HBPE) was added to the adhesive as a toughening agent. The resulting crosslinked protein adhesive bound wood with high strength and in some cases its force exceeded the force that the wood itself could withstand. In addition, the borate crosslinked protein adhesive displayed antimicrobial and flame-retardant properties. Simple borate chemistry can provide a way to produce low-cost, renewable, and high-performance materials. [ABSTRACT FROM AUTHOR]

Differing from the hot-pressing method in the manufacturing of traditional wood-rubber composites (WRCs), this study was aimed at fabricating WRCs using rubber processing to improve water resistance and mechanical properties. Three steps were used to make WRCs, namely, fiber-rubber mixing, tabletting, and the vulcanization molding process. Ninety-six WRC panels were made with wood fiber contents of 0%-50% at rotor rotational speeds of 15-45 rpm and filled coefficients of 0.55-0.75. Four regression equations, i.e., the tensile strength (Ts), elongation at break (Eb), hardness (Ha) and rebound resilience (Rr) as functions of fiber contents, rotational speed and filled coefficient, were derived and a nonlinear programming model were developed to obtain the optimum composite properties. Although the Ts, Eb and Rr of the panels were reduced, Ha was considerably increased by 17%-58% because of the wood fiber addition. Scanning electron microscope images indicated that fibers were well embedded in rubber matrix. The 24 h water absorption was only 1%-3%, which was much lower than commercial wood-based composites. [ABSTRACT FROM AUTHOR]

In this research, three different types of biocomposites were made from kenaf fiber/soy protein, kenaf fiber/DS 3530, and kenaf fiber/soy protein/DS 3530. Fourier transform infrared spectra of the biocomposites showed that there were chemical reactions among the kenaf fiber, soy flour, and BASF Acrodur resin. The hot-pressing time had a significant effect on the flexural properties and density of both the kenaf fiber/soy flour composites and kenaf fiber/BASF Acrodur resin composites. However, the effect was opposite for the composites from 10 to 20 min of hot pressing. As the hot-pressing time increased, the flexural properties and density increased for the kenaf fiber/soy flour composites and decreased for the other two composites with BASF Acrodur resin. BASF Acrodur resin reduced the hot-pressing time of the biocomposites. With 28 wt % BASF Acrodur resin (on the basis of 100% solid content) as a binder and with the biocomposites hot-pressed for 10 min, the swelling thickness and water absorption of the composites were reduced by 55 and 64%, and the flexural strength and modulus were improved by 72 and 188%, respectively. More simultaneous failures of the fiber and adhesive were observed at the fracture surface of the kenaf fiber/soy flour/BASF Acrodur resin composite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Cellulose nano-whiskers were used to enhance the performance of soybean meal-based adhesive. Soybean meal flour, cellulose nano-whiskers (CNW), sodium hydroxide (NaOH), and polyethylene glycol (PEG) were used to develop different adhesive formulations. The effect of adhesive components on water resistance of the adhesive was measured on the three-ply plywood (three cycle soak test). The viscosity and solid content of the adhesive were measured. The cross section of the cured adhesives was evaluated using scanning electron microscopy (SEM). The effect of the hot press parameters on the water resistance of the plywood bonded by soybean meal/CNW/NaOH/PEG adhesive was investigated. The results showed that using the CNW in the adhesive formulation improved the water resistance of the plywood by 20%. The plywood bonded by the soybean meal/CNW/NaOH/PEG adhesive met the interior plywood requirement (2000 (ANSI/HPVA HP-1)). Fewer holes and cracks, as well as a smooth surface were observed on the cross section of the cured adhesive after the incorporation of CNW. In the hot press process, the water resistance of the plywood bonded by the soybean meal/CNW/NaOH/PEG adhesive increased as the hot press temperature and time increased. [ABSTRACT FROM AUTHOR]

Soybean meal flour, polyethylene glycol (PEG), sodium hydroxide (NaOH), and a melamine-urea-formaldehyde (MUF) resin were used to formulate soybean meal/MUF resin adhesive. Effects of the adhesive components on the water resistance and formaldehyde emission were measured on three-ply plywood. The viscosity and solid content of the different adhesive formulations were measured. The functional groups of the cured adhesives were evaluated. The results showed that the wet shear strength of plywood bonded by soybean meal/NaOH adhesive increased by 33% to 0.61 MPa after adding NaOH into the adhesive formulation. Addition of PEG reduced the viscosity of the soybean meal/NaOH/PEG adhesive by 91% to 34,489 cP. By using the MUF resin, the solid content of the soybean meal/MUF resin adhesive was improved to 39.2%, the viscosity of the adhesive was further reduced by 37% to 21,727 cP, and the wet shear strength of plywood bonded by the adhesive was increased to 0.95 MPa, which met the interior plywood requirements (≥0.7 MPa). The formaldehyde emission of plywood bonded by the soybean meal/MUF resin adhesive was obtained at 0.28 mg/L, which met the strictest requirement of the China National Standard (≤0.5 mg/L). FTIR showed using the MUF resin formed more CH2 group in the cured adhesive. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

The effects of using sodium dodecyl sulfate (SDS) and a modified polyacrylic acid solution (MPA) on a soybean meal adhesive were investigated. Three-ply plywood specimens were fabricated to measure the water resistance of the adhesive (three-cycle soak test). The viscosity and solid content of the adhesive were measured. The cross-section and functional groups of the cured adhesive were evaluated using scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The results showed that using SDS improved the water resistance of the soybean meal adhesive by 30%. After incorporating MPA, the water resistance of the soybean meal/SDS/MPA adhesive was further improved by 60%, the viscosity of the adhesive was reduced by 81%, and the solid content of the adhesive increased by 15%. The plywood bonded by the soybean meal/SDS/MPA adhesive met the interior plywood requirements. SEM results showed no holes and cracks on the cross-section of the cured soybean meal/SDS/MPA adhesive. FTIR analysis indicated that more peptide linkages were formed in the cured adhesive as MPA was incorporated. [ABSTRACT FROM AUTHOR]

Wood used in outdoor applications needs to undergo either chemical or thermal treatment to improve its decay resistance. Thermal treatment permits to avoid the use of toxic chemicals, increases the dimensional stability and gives a dark color to the wood. However, this process deteriorates the mechanical properties of wood, i.e., the wood becomes more fragile and rigid. The chemical transformation of wood that takes place during the heat treatment changes the interaction between the wood surface and the adhesive. In this work, the interfacial bonding strength (the resistance to the shear stress by compression in parallel direction to the glued interface) and cyclic delamination (resistance to delamination during accelerated exposure) for different wood species and adhesives were tested in accordance with the ASTM D2559 standard. Four wood species: scott pine (Pinus sylvestris), aspen (Populus tremuloides), yellow poplar (Liriodendron tulipifera) and jack pine (Pinus banksiana) both treated and non-treated, and two structural adhesives, phenol resorcinol formaldehyde (PRF) and polyurethane (PUR), were used in the testing. Among the studied species, jack pine is found to be the easiest to bond, while aspen is found to be the most difficult. With the wood species and adhesives evaluated in this study, non-treated wood is found to provide a better bonding strength than the treated wood. [ABSTRACT FROM AUTHOR]

Polysaccharide-Based Adhesives: A High-Performance Bio-Adhesive Using Hyperbranched Aminated Soybean Polysaccharide and Bio-Based Epoxide (Adv. Keywords: hot-pressing conditions; hyperbranched cross-linking structure; industrial applications; polysaccharide-based adhesive; soybean polysaccharide EN hot-pressing conditions hyperbranched cross-linking structure industrial applications polysaccharide-based adhesive soybean polysaccharide 1 1 1 05/09/20 20200507 NES 200507 A novel water-soluble soybean polysaccharide (WSSPS)-based adhesive is developed by hyperbranched polyamide grafting in conjunction with eco-friendly cross-linking. Hot-pressing conditions, hyperbranched cross-linking structure, industrial applications, polysaccharide-based adhesive, soybean polysaccharide. [Extracted from the article]

Bio-based adhesives have low water resistance and they are less durable than synthetic adhesives, which limits their exterior applications. In this study, a bio adhesive was developed from soybean meal and larch tannin that was designed for exterior use. Phenol hydroxymethylated tannin oligomer (PHTO) was synthesized and then mixed with soybean meal flour in order to obtain a soybean meal-based adhesive (SPA). The results showed that the moisture absorption rate, residual rate, and solid content of SPA with 10 wt % PHTO (mass ratio with respect to the entire adhesive) were improved by 22.8%, 11.6%, and 6.8%, respectively, as compared with that of pure SPA. The wet shear strength of plywood with SPA with 10 wt % PHTO (boiling in 100 °C water for 3 h) was 1.04 MPa when compared with 0 MPa of pure SPA. This met the bond strength requirement of exterior-use plywood (GB/T 9846.3-2004). This improved adhesive performance was mainly due to the formation of a crosslinked structure between the PHTO and the protein and also PHTO self-crosslinking. The formaldehyde emission of the resulting plywood was the same as that of solid wood. The PHTO-modified SPA can potentially extend the applications of SPAs from interior to exterior plywood. [ABSTRACT FROM AUTHOR]

Despite the recent advances in protein-based adhesives, achieving strong adhesion and mold resistance in wet environment is challenging. Herein, a facile fabrication technology of preparing tough bio-adhesive by incorporating soybean meal and blood meal is presented. Inspired by the marine mussel byssi and brown algae, metal coordination was introduced into a loosely bound protein system to construct multiple chemical cross-linking networks. Mixed alkali-modified blood meal (mBM) was mixed with soybean meal, then 1,6-hexane dioldiglycidyl ether (HDE) and zinc ion were introduced to fabricate soybean meal and blood meal-based adhesives. The attained adhesives exhibited good thermal stability, water resistance (the wet shear strength is 1.1 MPa), and mold resistance, with appropriate solid content (34.3%) and relatively low moisture uptake (11.9%). These outstanding performances would be attributed to the reaction of 1,6-hexane dioldiglycidyl ether with protein to form a preliminary cross-linking network; subsequently, the coordination of zinc ions with amino or carboxyl strengthened and toughened the adhesive. Finally, the calcium ions gelled the adhesives, providing cohesion force and making the network structure more compact. This study realized the value-added utilization of protein co-products and developed a new eco-friendly bio-based adhesive. [ABSTRACT FROM AUTHOR]

Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving crosslinking density is generally accompanied by a toughness reduction of the adhesive. Herein, we developed a flexible long-chain starch with a hyper-branched structure (HD), and incorporated it with SM and a crosslinking agent to prepare a novel SM adhesive. Results showed that this adhesive exhibited both excellent water resistance and enhanced toughness. The wet bond strength of plywood fabricated using this adhesive was 354.5% higher than that of SM adhesive. These achievements are because introducing HD with hyper-branched groups enhanced crosslinking density, while HD's flexible long-chain structure improved toughness of the adhesive. This HD can promote the development of tough and hydrophobic bio-based composites. [ABSTRACT FROM AUTHOR]

Design of eco-friendly, non-formaldehyde and flame retardant wood adhesives is in high demand for the wood industry, which can help to alleviate environmental stress and human health concerns. Magnesium oxychloride cement (MOC) can reduce CO 2 emission and increase the value-added utilization of potash industry wastes, making it an ideal alternative to hazardous formaldehyde-based adhesives. However, its practical application usually suffers from poor water resistance and the filtering effect of wood. Inspired by the porous structure of cuttlebone, a facile yet powerful strategy is presented to prepare MOC adhesive with outstanding water resistance, compressive strength and adhesive ability to wood through introducing biochar. The naturally porous structure of biochar can form a protective core-shell structure and encapsulation with hydration products to stabilize phase 5 (5Mg(OH) 2 ·MgCl 2 ·8H 2 O), avoid crack extension and mitigate the filtering effect of wood. Meanwhile, the abundant functional groups of biochar can construct multiple interactions with Mg2+, which contributes to forming an internal network with excellent cohesion strength. Compared with pristine MOC, the obtained MOC/Biochar exhibited 102.33%, 32.33% and 31.45% increases in water resistance, compressive strength and wet adhesion strength, respectively. This work provides a promising strategy in preparing eco-friendly MOC-based adhesive from agricultural and industrial by-products to reduce environmental hazards. [Display omitted] • An eco-friendly, flame retardant and non-formaldehyde wood adhesive was proposed. • Biochar was used to form multiple interactions in magnesium oxychloride cement. • The composite showed integrated water resistance and compressive strength. • Adhesive alleviated the filtering effect of wood and showed good adhesion strength. [ABSTRACT FROM AUTHOR]

• Simultaneously flame retarded, high bonding strength and formaldehyde-free adhesive was fabricated. • A stable system of organic–inorganic hybridization was constructed. • The wet shear bond strength of lap plate increased by 53.5%. • Inorganic adhesive greatly reduced total heat release and total smoke production rate of wood-based composites. Developing high performance and non-toxic adhesives to replace the petroleum-based adhesives are highly desirable for wood industry. The use of magnesium oxychloride cement (MOC) inorganic adhesive is beneficial for the protection of human health and conservation of fossil resources. However, the low initial viscosity and poor water resistance have limited their application in plywood fabrication. In this study, polyacrylamide (PAM) and sodium polyacrylate (PAAS) were added to the adhesive as organic agents to construct wood-based composites by the organic–inorganic hybrid strategy. The MOC would be solidified by a cold-pressing method, forming a formaldehyde-free wood adhesive with high bonding performance. The addition of PAM efficiently improved the stability and processability of MOC, while PAAS improved the water resistance of MOC by inducing Mg2+ chelation and transforming the phase 5 structure. This adhesive exhibited a 53.5% increase in wet shear strength in contrast with the unmodified MOC adhesive. In addition, the MOC adhesive bonded wood-based composites showed high flame-retardant properties. [ABSTRACT FROM AUTHOR]

Developing a clean and environmentally-friendly soy protein adhesive to replace formaldehyde-based adhesive is of great significance for sustainable development of resources and human health. Due to the high molecular weight of protein, the resultant soy protein adhesive has a high viscosity and unstable bonding performance, which limit their application on plywood fabrication. Inspiring by theory of molecular recombination enhancing material properties, in this study, bromelain was used to degraded soy protein molecules into small polypeptide chains; a bio-derived cross-linker, triglycidylamine (TGA), was employed to recombine these polypeptide chains to develop a new cleaner soy protein-based adhesive with an excellent and stable bonding performance. The results showed that the molecular weight of soy protein decreased from 10 to 170 KDa to below 25 KDa by adding 0.4% bromelain. Using 3% TGA and 0.1% bromelain, the resultant adhesive viscosity decreased 95% and the wet shear strength increased 76.2% to 1.11 MPa compared with that of the unmodified adhesive. At the same time, the adhesive distribution, bonding stability have been improved significantly. More important, this molecular recombination soy protein adhesive reduced the amount of crosslinker more than 50% compared to other cross-linked modified soy protein adhesives. Image 1 • Bromelain has been used to degrade soy protein molecules into polypeptide chains. • A bio-derived crosslinker recombines polypeptide chains to develop a new adhesive. • The viscosity of resultant adhesive decreased by 95%, forming a uniform bond line. • The wet shear strength of resultant plywood increased by 76.2% to 1.11 MPa. • Molecular recombinant reduces the addition of crosslinker over 50% with a stable bonding. [ABSTRACT FROM AUTHOR]

Developing multifunctional adhesives with exceptional cold-pressing strength, water resistance, toughness, and mildew resistance remains challenging. Herein, inspired by oysters, a multifunctional organic-inorganic hybrid soybean meal (SM)-based adhesive was fabricated by incorporating amino-modified carbon dots functionalized silica nanoparticles (CDs@SiO 2) and dialdehyde chitosan (DCS) into SM matrix. DCS effectively enhanced the interface interactions of organic-inorganic phases and the rigid nanofillers CDs@SiO 2 uniformly dispersed in the SM matrix, which provided energy dissipation to improve the adhesive's toughness. Owing to the stiff skeleton structure and enhanced crosslinking density, the crosslinker-modified SM (MSM)/DCS/CDs@SiO 2 –2 wood adhesive exhibited outstanding cold-pressing strength (0.74 MPa), wet shear strength (1.36 MPa), and long-term water resistance (49 d). Additionally, the resultant adhesive showed superior antimildew and antibacterial properties benefiting from the introduction of DCS. Intriguingly, the fluorescent properties endowed by carbon dots further broadened the application of adhesives for realizing security testing. This study opens a new pathway for the synthesis of multifunctional biomass adhesives in industrial and household applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The introduction of 2D graphene into the soybean protein (SP) adhesive is expected to enhance its mechanical performance. However, insufficient binding of the two materials inevitably leads to the resulting composite having limited mechanical strength. Using phytic acid (PA) and a supramolecular self-assembly strategy, hard graphene oxide (GO) was first assembled with PA to form a supramolecular polymer, PA-co-GO, that has a "bricks and mortar" structure as a result of strong non-covalent interactions. PA-co-GO was then further combined with SP in the presence of the long-chain epoxy compound neopentyl glycol diglycidyl ether (NG) to produce a novel biopolymer-based adhesive PA-co-GO/NG/SP. The prepared adhesive has a moisture-insensitive interface as a result of non-covalent/covalent bonds and a "bricks and mortar" microstructure that allows the dissipation of energy, resulting in an enhancement in the water-resistant bonding strength of the material, with a 345% increase in its wet bonding strength compared with the unmodified SP adhesive. Additionally, the combination of the heat shielding of the GO and catalytic carbonization of PA resulted in the adhesive having excellent flame retardant properties. The structure and morphology of the materials were characterized using atomic force microscopy (AFM), dynamic light scattering (DLS), Fourier-transform infrared (FTIR), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and solid-state 13C NMR. Overall, a new clean route for preparing green high-performance biopolymer-based adhesives is described, with potential applications for sustainable agricultural byproducts. [Display omitted] • A supramolecular polymer PA-co-GO was used to improve the performance of adhesive. • The adhesive has a moisture-insensitive interface due to non-covalent/covalent bonds. • A "bricks and mortar" structure increases energy dissipation and improves strength. • The wet bonding strength of the prepared adhesives is greatly improved by 345%. [ABSTRACT FROM AUTHOR]

It is very important for industrial production to develop a strong bonding and multifunctional soy protein (SP)-based adhesive with excellent coating property and high prepressing strength especially for wet veneer. Inspired by mussels, catechol structure was grafted to soybean protein molecules (SPU) by ring opening reaction and free radical polymerization, which endowed the adhesive excellent coating performance on wet veneer. Inspired by oysters, magnesium hydroxide with unsaturated bond (MH@A172) was synthesized, and then mixed with SPU to obtain an organic-inorganic hybrid adhesive (SPU/MH@A172). During the curing process, the synergistic enhancement of the formed cross-linking structure and inorganic mineralization strategy improved the cohesion of SPU/MH@A172 adhesive and endowed strong bonding strength of prepared plywood. That is, when the SPU/MH@A172 adhesive was applied to wood veneer of 100% moisture content, it can be evenly coated and the prepressing bonding strength at 20 °C with 3 h reached 0.53 MPa, which meets the bonding strength requirement of plate forming (≥0.4 MPa). After hot-curing process, the wet and dry shear strength of the prepared plywood reached 1.07 MPa and 2.03 MPa, respectively. In addition, the adhesive had excellent stiffness (45.21 GPa) and micro adhesion (4.62 nN). Importantly, adhesives exhibited excellent mildew resistance (14 days, grade 2), flame retardancy (HRC = 114 kJ/g), low smoke suppression (Ds_max = 95.09) and volatile organic compound release (6.43*106 mg/m2⋅h). Therefore, this collaborative bionic strategy provides a possibility for the development and functional modification of underwater adhesive, film, hydrogels and composite materials. [Display omitted] • A multifunctional soy protein-based adhesive was developed by constructing organic-inorganic mineralization structure. • The prepressing strength of veneer with 100% moisture content at 20 °C and 3 h reaches 0.53 MPa. • The wet and dry shear strength of the prepared plywood reach 1.07 MPa and 2.03 MPa. • The adhesive has excellent stiffness, micro adhesion, mildew resistance, flame retardancy. • The adhesive has low volatile organic compound release and is a product with ecological value. [ABSTRACT FROM AUTHOR]

It is still a great challenge to develop soybean protein adhesives with high strength and antimildew properties through a sustainable and facile strategy. Herein, water-soluble dialdehyde chitosan (DCS) was obtained by oxidizing chitosan (CS) and used to crosslink soybean meal (SM) to fabricate protein adhesives via the Schiff base reaction. This strategy is simple, all-biomass, and without additional crosslinkers. Owing to the covalent imine bonds and non-covalent hydrogen bonds interactions, the adhesion strength of SM/DCS-4 adhesive reached 1.47 MPa, satisfying the requirement for Type II interior plywood (≥ 0.7 MPa). More importantly, the protein adhesives showed excellent antimildew properties due to the amino and aldehyde groups of DCS and the Schiff base formation. The SM/DCS-4 adhesive exhibited long shelf life (7 d), which is beneficial for industrial applications. This study helps in preparing green and fully bio-based adhesives from agricultural and fishery wastes. [Display omitted] • Dialdehyde chitosan (DCS) acted as a functional crosslinker. • Highly dense imine bonds and hydrogen bonds strengthened the adhesive network. • DCS can improve the bonding strength and antimildew properties of the adhesive. • The soybean meal (SM)/DCS adhesive exhibited long shelf life (7 d). • The SM/DCS adhesive made full use of agricultural and fishery wastes. [ABSTRACT FROM AUTHOR]

The preparation of a soybean protein adhesive with good prepressing intensity, mildew proof, flame retardant, and high bond strength are conducive to the wide application of a soybean protein adhesive, which is important but challenging for the wood-based panel industry. In this study, two hyperbranched functional polymers were designed. Hyperbranched polyamide (HP) was grafted by 3-hydroxyphenylphosphinyl-propanoic acid (PPA) to obtain PPA@HP and then combined with self-synthesized epoxidized tannin (ETA) to modify the soybean protein adhesive. The hyperbranched functional polymer PPA@HP and ETA reacted with soybean protein to form a hyperbranched cross-linking structure and a hydrogen bond network, which noticeably improved the toughness and bond strength of the adhesive. The wet shear strength of the resultant plywood was improved by 110.9% to 1.35 MPa. The formed hyperbranched hydrogen bond network also significantly improved the prepressing intensity (by 129.0% to 0.71 MPa). In addition, the anti-mildew time increased from 24 h to 120 h. The time to block combustibles increased from 5 s to 80 s, and the limiting oxygen index improved from 23.5% to 38.5%. The use of hyperbranched functional polymers created covalent and non-covalent hybrid networks provides an effective and convenient strategy for developing high-strength and multifunctional composites, such as bio-adhesives, hydrogels, and films. • Two hyperbranched functional polymer PPA@HP and ETA was designed and tested. • PPA@HP and ETA were combined with SPI to obtain protein-based adhesive. • The adhesive has high bond strength (1.35 MPa) and prepressing intensity (0.71 MPa). • The anti-mildew time and the limiting oxygen index were reached 120 h and 38.5%. • A new facile and universality strategy for fabricating multifunction biocomposites. [ABSTRACT FROM AUTHOR]

[Display omitted] • A renewable resource of soybean meal was used to prepare an eco-friendly adhesive. • Dynamic physical and stable chemical double cross-linking network was constructed. • The bonding strength and water-resistance of adhesive were significantly improved. • The anti-mildew of soy protein adhesive was enhanced and extends the storage life. • A new facile and universality strategy for fabricating anti-mildew protein adhesive. Soybean meal (SM) adhesive is a promising alternative to petroleum-based ones. However, the poor water resistance, low bonding strength, and susceptibility to mildew limit its industrial application. Inspired by the micro-nano micelle structure's strengthening mechanism, a facile and green method of synthesizing a high-performance soy protein adhesive by a dual cross-linking strategy was reported. The in-situ self-assembled micelles of benzyldodecyldimethylammonium bromide (BDAB) interacted with protein chains via dynamical bonds, while 1,6-hexanediol diglycidyl ether (HDE) acted as the flexible cross-linker. The BDAB micelles interact with protein chains via non-covalent electrostatic interactions, improving the cross-linking density of the network system and the micelles with numerous amino cations exhibit efficient anti-bacterial properties. The as-obtained adhesive exhibits excellent mechanical properties and stable network structure, showing strong bonding strength and water resistance (2.22 and 1.25 MPa). Especially, the incorporation of HDE and BDAB imparts the modified SM adhesive with excellent antifungal and antibacterial (E. coli and S. aureus) performances, significantly extending the adhesive storage life. Additionally, this work provides a new facile and universal strategy for fabricating formaldehyde-free, environment-friendly, and renewable protein-based adhesives, which is a promising alternative to traditional adhesives in the wood industry. [ABSTRACT FROM AUTHOR]

Natural materials (like teeth, bone, wood, bamboo, etc.) with organized hierarchical structures usually exhibit exceptional characteristics of both high stiffness and toughness. Bioinspired by this structure, design of functionalized hierarchical fibers has become an effective reinforcement strategy in fiber-reinforced polymer composites. In this work, bioinspired functionalized hierarchical fibers were constructed by anchoring catechol-modified metal-organic frameworks (MOFs) onto bamboo fiber surfaces which were then used as efficient strengthening phases to enhance the performance of soybean meal-based adhesives. The catechol-modified MOFs on fibers can form multiple interactions with a soybean meal matrix, whilst a hierarchical structures design for fibers can create a material gradient at the interval with a largely mismatched elasticity, which, remarkably, can decrease the stress concentration and thereby enhance energy dissipation in this region. As a result, the wet/dry shear strengths of the resultant adhesives were increased by 96.87% and 66.46%, and reached to 1.26 and 2.68 MPa, respectively. Also, the reinforcing mechanism of functionalized hierarchical fibers modified adhesives was proposed. We conceive that the functionalized hierarchical fibers as a bioinspired structural reinforcement has great potential for bionic adhesive applications. It also provides an effective reinforcement strategy for structural composites. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A hyperbranched catechol polymers (DBA@HBPA) was synthesized to mineralize Ag+. • The reaction among CPBA, SPI, and DBA@HBPA built a water-resistant cross-linking network. • The adhesive with anti-mildew/anti-bacterial properties had a long-term adhesion for 12 d. • The adhesive has high bond strength, good toughness, fire resistance and low VOCs emission. Developing a strong soybean protein adhesive with long-term adhesion and multiple functions to replace petroleum-based adhesives is important but challenging. Inspired by the biomineralization strategy, soybean protein as a matrix, 4-carboxyphenylboronic acid as a crosslinker, a self-synthesized hyperbranched catechol polymer (DBA@HBPA) as a catechol group donor, and AgNO 3 as an Ag+ donor were used to develop a strong and multifunctional soybean protein adhesive. The results showed that the coating and prepressing performance of the adhesive was improved by the addition of DBA@HBPA. The prepressing intensity of the adhesive improved by 156% and reached 0.89 MPa. Benefiting from the dynamic balance of quinone-catechol produced by Ag NPs and the super antimildew and antibacterial properties of Ag NPs and boron, the adhesive exhibited long-term adhesion behavior (pot life of 12 d), excellent mildew resistance (30 d), and antibacterial properties (colony count of 0). The wet shear strength of plywood prepared by the resultant adhesive was 1.28 MPa, which was 106% higher than that of the SPI adhesive. In addition, the resultant adhesive exhibited fire retardancy (LOI = 37.4%) and low VOCs emission (4.26*106 mg/m2·h). This biomimetic design provides a novel and efficient strategy for the preparation of high-adhesion, multifunctional biomass composite adhesives. [ABSTRACT FROM AUTHOR]

[Display omitted] • A muscle tissue-inspired design strategy for enhanced protein based adhesive was proposed. • The wet shear strength of the adhesive increased by 214%. • The existence of sacrificial structure increased the adhesion work by 802%. • The adhesive exhibited remarkably improved mildew resistance. Protein based adhesive is limited by poor mechanical properties and water resistance. Inspired by the structure of muscle tissue, a complex structure of layered double hydroxide (LDH) anchored chicken feather fiber (CFF) and tannic acid (TA) was constructed by self-assembly process, forming a novel organic–inorganic hybrid reinforcement structure (CFF-LDH-TA). CFF-LDH-TA was closely combined with soybean meal (SM) through covalent and hydrogen bond multiple interactions. TA simulated the function of connective tissue around fibers, significantly improving the cohesion of SM based adhesive through effective energy dissipation and load transfer. Due to the increased crosslinking density, the dry and wet shear strengths of SM/CFF-LDH-TA reached 2.12 and 1.60 MPa, respectively, which were 50 % and 214 % higher than original SM adhesive, and significantly exceeded the strength of several commercialized formaldehyde adhesives. The existence of bridging effect and sacrificial structure improved toughness of the adhesive, the work of adhesion increased by 802 %, reached 830 mJ. In addition, the SM/CFF-LDH-TA adhesive had better anti-mold and flame retardant ability. More importantly, the cost was lower than the commercial SM based adhesive. This simple and green preparation method provided a new strategy for the production of high-performance, multifunctional and economically effective SM based adhesive. [ABSTRACT FROM AUTHOR]

Epoxide modification effectively improves the water tolerance of soy protein adhesives, showing great potential in the commercial application as alternatives to petroleum-derived formaldehyde-based adhesives. However, epoxide-modified adhesives still present problematic limitations, such as poor mildew resistance and high hot-pressing temperature. In this study, a curing system based on radical polymerization was designed and developed to prepare soy protein adhesives, instead of building a traditional epoxide cross-linking structure. First, allyl glycidyl ether (G) was grafted onto a soy protein (SP) molecule to obtain soy protein with unsaturated double bonds (G@SP). Allicin (A) was then used as a cross-linker to build a cross-linking structure (G@SP/A) via free-radical polymerization to enhance the bond performance of the adhesive. Relative to that of pure SP adhesive, the wet shear strength (WSS) and dry shear strength (DSS) of plywood bonded with the G@SP/A adhesive increased by 108% and 45%, reaching 1.08 MPa and 1.84 MPa, respectively, at 120 °C pressing temperature. Notably, the G@SP/A adhesive showed superior antibacterial (Escherichia coli and Staphylococcus aureus) activity, high mildew resistance (35 d shelf life), good cytocompatibility, and biodegradability (30 d). Moreover, the WSS of plywood bonded with the G@SP/A adhesive at 80 °C for 6 min and 20 °C for 72 h reached 1.08 MPa and 1.12 MPa, respectively, indicating the sufficient low-temperature curing ability of the resultant adhesive. Thus, building a cross-linking structure by free-radical polymerization can be extended to improve the performance of film composites, other adhesives, and engineering materials. • Free radical polymerization curing system was used to prepare soy protein adhesive. • The resultant adhesive has excellent antibacterial and mildew proof ability. • The resultant adhesive has good cytocompatibility and biodegradability. • The wet shear strength of resultant plywood increased by 108% to 1.08 MPa. • The resultant adhesive has good low temperature curing ability. [ABSTRACT FROM AUTHOR]

Plant-derived protein adhesives have attracted extensive research interest in recent years as effective alternatives to nonrenewable and nonbiodegradable formaldehyde-based adhesives. However, owing to their insufficient bonding strength and poor mildew resistance, it has been challenging for biopolymer adhesives to achieve strong and durable adhesion performance. Inspired by insect cuticles, we report a green and versatile strategy for the fabrication of a strong, mildew-resistant, antibacterial soy protein (SP)-based adhesive via phenol-amine synergy and biomineralization reinforcement. Gallic acid (GA), as a phenolic glue molecule, was co-assembled with hydroxyapatite (HAP) through Ca2+–phenolic coordination bonds to prepare GA-functionalized HAP (GA@HAP) nanoparticles. Moreover, ε -polylysine (PL) with abundant amino groups was used for grafting to the phenolic GA@HAP nanoparticles through a Schiff base reaction. Owing to multiple cross-linking and the inorganic–organic hybrid system, the wet shear strength of the SP/PL/GA@HAP adhesive increased considerably to 1.09 MPa, 127% higher than the unmodified SP adhesive. The cationic PL polymer endowed the protein adhesive with desirable antifungal and antibacterial properties, synergistically with the phenolic components in GA@HAP. In addition, the resultant adhesive exhibited enhanced flame retardation, thermal stability, and water resistance. This simple and versatile strategy could lead to advances in the development of high-performance biopolymer materials for biological and engineering applications including adhesives, hydrogels, and films. [Display omitted] • A mineral–organic hybrid network was constructed in a biopolymer system. • Hydroxyapatite nanoparticles were functionalized with phenolic glue molecules. • Multifunctional soy protein adhesive was fabricated via phenol-amine chemistry. • The wet shear strength of the prepared adhesive was significantly improved by 127%. • Biopolymer adhesive showed enhanced anti-mildew and antibacterial properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • The nanophase-reinforced organic–inorganic hybrid structure was successful constructed. • Using PA as crosslink agent instead of traditional epoxide linked SPI and G-co-Q hybrid. • The resultant adhesive has a high performance with excellent flame-retardant, mildew resistance and antibacterial. • The wet shear strength of the resultant plywood increased by 78.7% to 1.09 MPa. • The plywood bonded by our adhesive is the absorption dominated EMI shielding material with low reflection characteristics. The development of multifunctional adhesive with high bond strength, toughness, mildew resistance, antibacterial properties, flame retardancy, and electromagnetic (EMI) shielding properties has drawn interest and simultaneously presents a challenge in the wood panel industry. Herein, inspired by the organic–inorganic hybrid structure of oysters, an antibacterial agent quaternary ammonium salted hyperbranched polyamide (QHBPA), was synthesized to modify graphene nanosheets (GNSs) via cation-π interaction, eventually forming a G-co-Q hybrid. The G-co-Q hybrid was then combined with soy protein isolate (SPI) and phytic acid (PA) to develop a plywood adhesive with an organic–inorganic hybrid structure via electrostatic interactions and hydrogen bonds. The resultant adhesive exhibited good mildew resistance and antibacterial activity (144 h shelf life). Compared with the SPI adhesive, the dry and wet shear strengths of the plywood with the SPI/PA/G-co-Q adhesive increased by 76.6% and 78.7%, respectively. Meanwhile, non-covalent cross-linking and the formation of an organic–inorganic hybrid structure endowed the adhesive with excellent toughness. Furthermore, the limiting oxygen index (LOI) of the resultant adhesive was 35.5%, reflecting an increase of 49.1% relative to that of the SPI adhesive, indicating that the adhesive possesses superior flame retardancy. Importantly, owing to its unique isolated multilayered structure, the plywood bonded by our adhesive is an absorption dominated EMI shielding material with low reflection characteristics and displays a desirable EMI shielding effectiveness of 43 dB. Therefore, this study provides a creative insight into the design of high value-added and multifunctional plywood with promising application prospects not only in conventional wood-based panels but also in advanced EMI shielding materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SiO 2 nanohybrid (DP@SiO 2) was successful synthetized. • Using HCCP as crosslink agent instead of traditional epoxide linked SPI and DP@SiO 2. • The resultant adhesive has a high performance with excellent flame-retardant and coating ability. • The wet shear strength of the resultant plywood increased by 143% to 1.46 MPa. • The limiting oxygen index (LOI) of the resultant adhesive was as high as 39.4%. Developing an environment-friendly soy protein adhesive with high bonding strength and flame retardancy has drawn interest and simultaneously presented a challenge in the wood panel industry. Prompted by the organic–inorganic hybrid of oysters, this study proposes a nanohybrid (DP@SiO 2) consisting of the nano silica (SiO 2) and polyethyleneimine (PEI) via electrostatic interaction and grafting 3, 4-dihydroxybenzaldehyde (DBA) by Schiff base reaction. The obtained structure was then combined with a multifunctional cross-linker hexachlorocyclotriphosphazene (HCCP) and soy protein isolate (SPI) to develop a plywood adhesive. The resultant adhesive exhibited good coating ability and prepressing properties, which were attributable to the catechol groups of DP@SiO 2 and the reaction between protein and HCCP. Compared with that of the SPI adhesive, the prepressing strength of plywood with the SPI/HCCP/DP@SiO 2 adhesive was increased by 304%. The dry and wet shear strengths of the plywood adhesive were 110% and 143% higher than those of the SPI adhesive, respectively, which were attributable to the formation of the cross-linking and organic–inorganic hybrid structure, and improvement in adhesive toughness caused by the combination of covalent and multiple hydrogen bonds. The limiting oxygen index (LOI) of the resultant adhesive was 39.4%, reflecting an increase of 71% relative to that of the SPI adhesive, indicating that the adhesive has excellent flame retardancy. This efficient organic–inorganic hybrid strategy can promote the enhancement and functional modification of underwater adhesives, hydrogel, and composite materials. [ABSTRACT FROM AUTHOR]

Bioinspired strategies for preparing multifunctional hydrogels have drawn attention. Among these hydrogels, the adhesive types have been extensively studied, However, most of them exhibit poor mechanical properties, short-term adhesion, and no antibacterial activity. Inspired by the mussel adhesion mechanism, an adhesive hydrogel made from tannic acid (TA), acrylamide (AM), and soy protein isolate (SPI) is presented in this study. The adhesive hydrogel showed a large tensile strain (932%), high tensile strength (45.8 kPa), high toughness (155.15 kJ·m−3), and ideal compressive properties owing to the formation of a hybrid double network (DN). This hydrogel exhibited satisfactory adhesion to various materials, including muscle tissue, metal, rubber, glass, plastic, and wood. The TA-PAM-SPI hydrogel also showed good antibacterial properties against Escherichia coli and Staphylococcus aureus , in addition to self-healing properties and biocompatibility. With these characteristics, the TA-PAM-SPI hydrogel was used as a wound dressing to accelerate wound healing and skin tissue regeneration. This study provides a convenient approach to preparing multifunctional hydrogels and promoting the application of SPI in biomedical materials. [Display omitted] • Inspired by mussels, a hybrid double-network soy protein-based composite hydrogel was developed. • The incorporation of SPI enhanced the cohesion and mechanical properties of hydrogel. • Hydrogel exhibited extremely high adhesiveness to hydrophilic/hydrophobic surface. • The resultant hydrogel has high biocompatibility and promotes wound healing. [ABSTRACT FROM AUTHOR]

The preparation of a soybean flour adhesive with good bonding and prepressing performance, toughness, mildew resistance, and fire retardancy to address the problem of formaldehyde pollution is crucial; however, it also presents a challenge. The core–shell structure can achieve various properties by tailoring-making the core–shell composition. In this study, a core–shell structure HBPA@TA with hyperbranched polyamide (HBPA) as the core and tannin (TA) as the shell was prepared and used to modify SF adhesives. The results showed that the pyrogallol group of the tannin shell endowed the adhesive with excellent prepressing performance (0.75 MPa of prepressing intension), toughness, and coating performance, rendering the adhesive more suitable for plywood fabrication. Owing to the dense tannins in HBPA@TA, the resultant adhesive exhibited superior mildew resistance (12 d). After closed-mouth placement for 12 d, the prepressing intension was reduced by 17.3% to 0.62 MPa, which still met the usage requirement. The wet shear strength of the plywood prepared using the resultant adhesive was 1.05 MPa—that is, 133.3% higher than that of the unmodified SF adhesive. The synthesized adhesive also showed antibacterial properties (inhibition zone = 8 mm), flame retardancy (LOI = 32.3%), and volatile organic compound release (6.86*106 mg/m2·h) lower than those of commonly used urea–formaldehyde resins and epoxy resins. [Display omitted] • A spherical hyperbranched core-shell structure HBPA@TA with pyrogallol groups was synthesized. • HBPA@TA as toughening and antifungal agent, and flame retardant modify soybean flour adhesive. • The prepared adhesive has good prepressing and coating performance, toughness, bond strength. • The prepared adhesive was mildew proof, antibacterial and flame retardant, low VOCs emission. [ABSTRACT FROM AUTHOR]

Plant-derived biomass adhesives are increasingly in demand to replace traditional non-biodegradable petrochemical materials. However, the insufficient mechanical strengths and poor antibacterial activities of biomaterials severely limit their applicability. Inspired by the amphiphilic characteristics of mussel protein, a dual-crosslinking strategy is reported here for preparing soy meal (SM)-based adhesives with excellent adhesion and antibacterial properties. Specifically, castor oil containing abundant hydroxyl groups was used to prepare the cationic waterborne polyurethane (WPU) dispersion. Subsequently, the dynamic glue bridges were synthesized from the tannic acid-functionalized borax (TA@BA) complexes via multiple coordination bonds. Finally, the enhanced cross-linking network system was then constructed in the protein matrix based on the synergy of dynamic covalent bonds, electrostatic interactions, and hydrogen bonds. As a result, the wet strength of the resultant adhesive significantly increased by 154.77% compared to the SM adhesive. Additionally, the resultant adhesive exhibited remarkably enhanced thermal stability, flame retardancy, and water resistance. Based on the synergistic effect of the cationic WPU, polyphenol components, and borate groups, the SM/WPU/TA@BA adhesive exhibited desirable anti-mildew and antibacterial properties. This biomimetic dual-crosslinking design therefore provides a novel and facile strategy for the preparation of high-performance biopolymer adhesives used in the fields of biology and engineering. [Display omitted] • A bioinspired dual-crosslinking strategy is used to prepare protein-based adhesives. • The cationic waterborne dispersion was synthesized from vegetable castor oil. • A dynamic glue bridge was formed by incorporating tannic acid-functionalized borax. • The water resistance of the protein-based composites was significantly improved. • The hybrid adhesive showed enhanced antibacterial properties and flame retardancy. [ABSTRACT FROM AUTHOR]

Soy protein-based adhesives show great prospects in replacing aldehydes resin adhesives to fabricate wood-based panels, however, high doses of synthetic resins as crosslinkers must be used to obtain good bonding performance. To reduce overreliance upon crosslinkers derived from fossil resources, a 100% bio-derived crosslinker-xylitol epoxide (EX) was synthesized from epichlorohydrin and xylitol, followed by blending with soy protein isolate (SPI) to create a functional biological adhesive. After using EX, the wet and dry shear strengths of plywood prepared by the SPI/4%EX adhesive increased by 138.6% and 55.6%, respectively, compared with the pure soy protein adhesive. This was attributable to the crosslinked network formed in adhesive and the enhanced adhesive toughness. The optimized process parameters of plywood prepared with EX-modified soy protein adhesive were 110 ℃, 1.3 min/mm and 0.8 MPa. The addition of EX also improved the mildew-resist property of the adhesive to 10 days, which prolonged the adhesive storage life and the service life of the resultant plywood. Therefore, EX could be utilized to enhance the mechanical and mildew-resist properties of protein-based materials, and shows great potential applications in adhesive, film, and hydrogel. • Xylitol was epoxidized to form a bio-based crosslinker (EX). • Using soy protein and 4% EX develops a 100% bio-derived wood adhesive. • The wet and dry shear strength of plywood increased by 138.6% and 55.6%. • The mildew resistance of resultant adhesive is more than ten days. [ABSTRACT FROM AUTHOR]

[Display omitted] The extraordinary strength and toughness of arthropod cuticle depend on phenol-amine chemistry and mineral reinforcement. A bio-inspired adhesive was engineered through introducing the cost-effective phenolic polymer accompanied with acid-stable montmorillonite mineral into amino-rich soy protein matrix. This adhesive reproduces the outstanding properties of arthropod cuticle, including high toughness and superior strength, and exhibited outstanding stiffness, mold resistance, flame retardancy. • An arthropod cuticle-inspired bio-based adhesive was prepared by phenol-amine chemistry and mineral enhancement. • The phenol-amine cross-linking and MMT reinforcement improved adhesive's adhesion strength. • The sacrificial interactions and micro-phase separation enhanced the adhesive's toughness. • The compatibility of hybrid system endows this adhesive with multi-functionality. Arthropod cuticles are extraordinarily stiff and strong due to phenol-amine chemistry and mineral reinforcement. Nevertheless, these cuticles require costly dopamine (phenol provider), acid-unstable minerals, enzymes that can be deactivated, making them difficult to imitate in artificial materials. Herein, the arthropod cuticle was mimicked by introducing a low-cost phenolic polymer (DP) and acid-stable montmorillonite into an amino-rich soy protein matrix (SPI) to develop a bio-based adhesive. Fe3+ was chosen as the oxidizing agent to trigger the oxidation of DP without using enzyme, while activating cross-linking between oxidized DP and SPI to cure the adhesive. This covalent cross-linking and mineral reinforcement strategy endowed the adhesive with a bonding strength (1.04 MPa) comparable to industrial-use adhesives, whereas its volatile organic compounds emission was about 10-fold lower than the industrial-use adhesives. The sacrificial bonds and microphase-separated structure formed from the adhesive resulted in a high toughness. Furthermore, this adhesive featured an outstanding stiffness (40.38 GPa), exceeding ten times that of normal plastics. Notably, this adhesive exhibited excellent mold resistance (288 h shelf life) and flame retardancy (level B 1 in GB 8624-2012). This efficient, eco-friendly, and low-cost bionic design strategy can advance the enhancement and functionalized modification of underwater adhesives, hydrogel, and composite materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A supramolecular strategy is reported to fabricate a soybean meal-based adhesive. • Cellulose nanofibrils act as templates to regulate biomineralization process. • Aminoclay is functionalized by tailor-made long alkyl chain quaternary salt. • The dry and wet shear strengths of the adhesive increase by 130% and 197%. • The adhesive has remarkably improved flame retardancy and antibacterial activity. Plant-derived protein adhesives have received widespread attention as sustainable alternatives to formaldehyde-based engineered wood products, but their practical applications are severely limited by the poor mechanical and antibacterial properties. Inspired by the amphiphilic and ionic features of mussel chemistry, we have developed a facile and green strategy for fabricating a soybean meal-based biomass adhesive with high bonding strength and antibacterial activity. The strategy incorporates a supramolecular system of biomineralized cellulose nanofibril (MCF) and a cationic long-alkyl-chain quaternary salt (LAQ) functionalized aminoclay (LAQ@AC). The functional MCF was prepared by in situ biomineralization of inorganic particles regulated by a cellulose nanofibril biotemplate, thus constructing a rigid mineralized skeleton structure in the protein matrix. The cohesion and adhesion strength of the protein composites were significantly improved by the supramolecular crosslinking of MCF/LAQ@AC hybrids via hydrogen bonds and electrostatic interactions. The dry and wet shear strengths of the resultant adhesive increased to 2.58 and 1.87 MPa, respectively, 130% and 197% higher than the pristine soybean meal adhesive, and remarkably exceeded those of other protein-based adhesives. By establishing a biomineralized architecture and a positively charged surface, the incorporated MCF/LAQ@AC hybrids endow the adhesive with desirable flame retardation and antibacterial activity. This novel and sustainable strategy provides a strong and stable supramolecular network for fabricating high-performance environmentally friendly biomass adhesives in biological and engineering applications. [ABSTRACT FROM AUTHOR]

The development of high-performance and sustainable bio-adhesive materials has attracted significant research attention in recent years. However, producing high-performance biopolymer materials with desirable mechanical and antibacterial properties remains a challenge. Herein, a mussel-mimetic strategy is reported to fabricate a soy protein (SP)-based composite film via aqueous co-assembly of 3-aminophenylboronic acid-functionalized cellulose nanofibril (AB@CNF) and hyperbranched polyester (HPE). The water-soluble HPE with numerous hydroxyl end groups was synthesized by using a facile and green method. Through enhanced dynamic covalent interactions and intermolecular sacrificial hydrogen bonds, the incorporated AB@CNF hybrids with conjugated cis -diols strongly interact and entangle with biopolymer chains in the hyperbranched network. As a result of multiple synergistic cross-linking, the toughness and strength of the SP/HPE/AB@CNF film increase by 574% and 346% to 10.05 MJ/m3 and 14.23 MPa, respectively. Additionally, the film offers excellent antibacterial activity, flame retardance, and thermal stability. This sustainable approach should open new avenues for the design and development of biomimetic plant-derived functional materials in biomass adhesive and active packaging. [Display omitted] • Protein-based adhesive is fabricated via mussel-inspired interface engineering. • Cellulose nanofibril is functionalized by 3-aminophenylboronic acid. • Water-soluble hyperbranched polyester is synthesized by a green one-pot method. • The toughness and strength of composite simultaneously increase by 574% and 346%. • The nanocomposite offers excellent antibacterial activity and flame retardance. [ABSTRACT FROM AUTHOR]

Traditional formaldehyde-based adhesives release toxic substances such as formaldehyde and phenol, which pollutes the environment, endangers human health, and relies on petrochemical resources excessively. Developing a strong soy protein adhesive with reasonable viscosity, toughness, and mildew resistance to replace formaldehyde-based adhesive is important and also a challenge for the industry of wood adhesive. In this study, a triple network structure including covalent bonds, hydrogen bonds and ionic bonds was built in soy protein adhesive. The results showed that compared with SPI adhesive, the viscosity of resultant adhesive decreased by 94.3% to 9952 mPa s, the dry and wet shear strength of resultant plywood increased by 33.9% (2.57 MPa) and 116% (1.36 MPa), respectively. The fracture strain of plywood increased by 36.4%, and the mildew resistance of adhesive increased from 1 day to more than 15 days. This improvement resulted from the adhesive's water resistance improvement by constructing the covalent network and the toughness increasing by the synergistic effect of hydrogen bonds and ionic bonds. This work provides a new method for the preparation of eco-friendly and high-performance adhesives and promotes the development of the green adhesive. Image 1 ● An eco-friendly adhesive with triple network structure was design and developed. ● The triple network structure consists of covalent, hydrogen and ionic bonds. ● The viscosity of resultant adhesive decreased by 94.3%. ● The dry/wet shear strength of plywood increased by 33.9% and 116%. ● The mildew resistance of adhesive increased from 1 day to more than 15 days. [ABSTRACT FROM AUTHOR]

The development of a formaldehyde-free, high-performance soybean meal (SM)-based adhesive for manufacturing cleaner wood-based panels is important for minimizing environmental pollution and promoting sustainability. However, the addition of chemical agents for this purpose negatively impacts the environment. Drawing from molecular recombination enhancement theory, a simple physical ultrasonic treatment was used to pretreat the SM to break its particles down and reduce the protein molecular weight. A bio-derived crosslinker was mixed into the SM to recombine the soy protein and prepare a clean, high-performance, bio-based adhesive requiring significantly lower amounts of chemical agents. After 20 min of ultrasonic treatment, the SM particle size was reduced by up to 48.8%, the quaternary structure of the soybean protein was destroyed, and the protein molecular weight decreased, exposing more active groups on the protein surface and resulting in an adhesive system that was both more stable and had a higher reactivity. Moreover, when adding only 4% crosslinker and zero denaturing agent, the ultrasonic treatment process increased the adhesive residual rate by 15.78%, decreased the moisture absorption rate by 25.26%, and improved the wet shear strength of the resultant plywood by 368.2% (to 1.03 MPa), meeting the requirements of the GB/T 9846.3–2004 standard for interior-use plywood. The loading of chemical agents was reduced by up to 650% in comparison to that used in other SM-based adhesive formulations reported in the literature. Thus, using a clean ultrasonic pretreatment process on the SM enabled the preparation of a high-performance, stable, and clean SM-based adhesive, thereby providing a promising option for the implementation of a bio-based product in industrial applications. Image 1 • A cleaner and high-performance soybean meal-based adhesive was developed. • Ultrasonic treatment breaks soybean protein molecule and exposes active groups. • Using only 4% crosslinker recombines protein molecule to develop a denser structure. • After 20 min UT, the wet shear strength of resultant plywood increased by 368%. • UT reduces the dosage of chemical reagent for soybean meal adhesive by up to 650%. [ABSTRACT FROM AUTHOR]

• The soybean derived daidzein was epoxidized to develop a bio-based crosslinker (DDE). • DDE was used to modify soy protein adhesive to form a 100% bio-based wood adhesive. • Using 6% DDE, the dry and wet shear strength of plywood increase by 52.3% and 164.4%. • DDE improves adhesive's mildew resistance and extends adhesive's shelf life to 12 h. Soy protein based adhesives showed great potential for replacing petroleum derived formaldehyde adhesives in the commercial wood industry. However, soy protein adhesives have several problematic limitations, particularly with respect to low water and mildew resistence. As such, in order for soy protein-based adhesives to be practically applicable on an industrial level, a multi-function bio-based crosslinker that resolves both low water and mildew resistance must be designed. In this study, we synthesized a multifunctional crosslink agent (DDE) by reacting soybean-derived daidzein with epichlorohydrin (ECH) and incorporating it into soy protein to parpare a 100% bio wood adhesive with significantly improved water and mildew resistances. The results showed that by using 6 wt% DDE in the adhesive formulation, the dry and wet shear strength of plywood bonded with the SPI/DDE adhesive increased by 52.3% and 164.4%, respectively, compared with that of SPI adhesive; and was shown to be 22.3% and 69.6% higher than that of the industrially used SPI/PAE adhesive. These improvements were attributed to formation of double cross-linked network and elevated adhesive toughness. Furthermore, the resultant adhesive's mildew resistance property were also improved with the addition of DDE, which extended the shelf life of adhesive and durability of the resultant plywood. Thus, this resultant DDE can be used to improve the mechanical properties and mildew resistance for bio-hydrogels or bio-based composites and polymers. [ABSTRACT FROM AUTHOR]

The development of high-performance and sustainable bio-based adhesives has become a significant strategy for solving concerns regarding environmental pollution, resource utilization, and public health in the material engineering and production industries. In this work, hyperbranched silicone was prepared and reacted with a catecholamine-based tannic acid and soybean meal to obtain a strong and antibacterial bio-based adhesive having a hyperbranched cross-linked structure. In addition, versatile copper ions were introduced into the adhesive to form multiple interfacial coordination bonds. The resulting intertwined dual network of metal coordination bonds and covalent crosslinks in the adhesive system improved the cross-link density and cohesive interactions of the adhesives, enhancing their adhesion strength and water resistance. The maximum wet shear strength of the modified adhesive was 1.27 MPa, which was 309.68% higher than that of the pristine adhesive. Sol-gel test showed that the swelling ratio of the modified adhesive decreased from 413.8% to 52.4%, while the insoluble fraction increased by 16.47%. Furthermore, the resulting adhesives exhibited a high bacterial resistance against Staphylococcus aureus and Escherichia coli. The formation of an intertwined dual network in a bio-based adhesive to achieve excellent properties is a promising approach for the fabrication of sustainable eco-friendly biopolymer materials from agricultural byproducts used to achieve a cleaner production. Image 10634 • A dual network of covalent crosslinks and metal coordination bonds was formed. • Hyperbranched silicone created a hyperbranched structure in the adhesive. • Copper ions formed multiple coordination bonds with tannic acid and protein. • The antimicrobial activity of the adhesive was significantly improved. • The wet shear strength of the resultant adhesive was improved by 309.68%. [ABSTRACT FROM AUTHOR]

The development of eco-friendly, non-formaldehyde, and high-performance bio-based adhesives is a great strategy for relieving environmental pressure and health concern, especially for the wood adhesive industry. In this work, a green soybean meal (SM)-based adhesive with excellent performance was developed by embedding modified kenaf fibers (KF). The synergistic bionic design with gecko structure and mussel chemistry endowed KF with improved rough surface and increased reactive sites, resulting in robust mechanical interlocking and multiple chemical crosslinking ability for SM-based adhesive. The resultant adhesive exhibited excellent bonding properties, compared to the SM adhesive, the wet shear strength was improved from 0.41 MPa to 1.52 MPa, and the moisture absorption was decreased from 10.1% to 8.6%. These results met the standard of type II plywood (≥0.7 MPa) according to the national standard of China (GB/T 9846.3-2004). This eco-friendly SM-based adhesive opens a new way to replace harmful formaldehyde-based adhesives and contributes to the development and use of agricultural and forestry byproducts for practical application. Image 1 • Biomimetic bio-based soybean adhesive was prepared via a facile method. • Kenaf fiber was functionalized with a modified Stöber technique (SSKF). • SSKF serves as multi-functional network skeleton. • Tannic acid (TA) acts as a "bridge" between the SM matrix and SSKF. • Adhesive strength and thermal stability of the resulting adhesive are improved. [ABSTRACT FROM AUTHOR]