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Eco-friendly soybean protein adhesives could be an ideal substitute for replacing traditional formaldehyde-based adhesives in wood industry. However, a large number of cross-linking agents are required in soy protein adhesive formulations to obtain sufficiently performing properties. Inspired by the high performance of nacre and branched structures, a hyper-branched amine (HBPA) was synthesized and grafted to graphene oxide (GO), generating a hyper-branched amine-functionalized GO (FGO). A novel soy protein-based adhesive was developed by mixing FGO with soy protein (SPI) and a low dose polyamidoamine-epichlorohydrin (PAE). Results showed that the addition of only 0.4 wt% FGO and 0.75 wt% PAE to the SPI adhesive formulation enhanced the wet shear strength of plywood to 1.18 MPa, which was 181% higher than that of the adhesive without enhancement. The enhanced performance is attributed to the denser cross-linking structure and improved toughness of the adhesive layer. Using FGO in the adhesive formulation also greatly reduced the concentration of the additive cross-linker by up to 78.6% when compared with values reported in the literature. Thus, using a hyper-branched functionalized nano-material to form an organic–inorganic hybrid structure is an effective and efficient strategy to reinforce the composites and polymers. It significantly reduces the chemical additive levels, and is a practical way to develop a sustainable product. [ABSTRACT FROM AUTHOR]

Soybean meal (SM)-based adhesive can solve the issues of formaldehyde emission and over-reliance of aldehyde-based resins but suffers from poor water resistance, weak adhesion strength, and high brittleness. Herein, a high-performance adhesive inspired by lobster cuticular sclerotization was developed using catechol-rich condensed tannin-functionalized boron nitride nanosheets (CT@BNNSs), amino-containing chitosan (CS), and SM (CT@BNNSs/CS/SM). The oxidative crosslinking between the catechol and amino, initiated by oxygen at high temperatures, formed a strengthened and water-resistant interior network. These strong intermolecular interactions induced by phenol–amine synergy accompanied by the reinforcement of uniformly dispersed BNNSs improved the load transfer and energy dissipation capacity, endowing the adhesive with great cohesion strength. Given these synergistic effects, the biomimetic CT@BNNSs/CS/SM adhesive caused noticeable improvements in water tolerance, mechanical strength, and toughness over the neat SM adhesive, e.g., enhanced wet shear strength (1.46 vs. 0.66 MPa, respectively), boiling water shear strength (0.92 vs. 0.43 MPa, respectively), and debonding work (0.368 vs. 0.113 J, respectively). Thus, this study provided a green and low-cost bionic strategy for the preparation of high-performance biomass adhesives. • An advanced adhesive inspired by lobster cuticular sclerotization is reported. • Oxygen at high temperatures initiated the crosslinking between CT@BNNSs and CS/SM. • Such phenol–amine synergy endowed the adhesive with great cohesion strength. • Strong intermolecular interactions and BNNSs reinforcement improved the adhesive's toughness. [ABSTRACT FROM AUTHOR]

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]

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 (C N) 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. • Ultrasonic treats lignin to form catechol structure (UAL) and combine with SPI to obtain adhesive. • Dynamic covalent/hydrogen hybrid networks were constructed in adhesive system. • The SPI/UAL adhesive has good coating, prepressing intension, and bonding performance. • The SPI/UAL adhesive exhibited good antibacterial, flame-retardant, and mildew resistance. • The resultant wood-based panel was reusable and biodegradable. [ABSTRACT FROM AUTHOR]

Developing low-cost renewable bio-based adhesives with excellent properties remains a challenge. Soybean meal (SM) adhesives have gained widespread attention for being green. However, it still has the problems of poor water resistance, low toughness, and easy to mildew. Herein, a waterborne polyurethane (TWPU) with carboxyl side chains was synthesized from tartaric acid (TA). It was used as chelating ligands to form the metal chelating to synergistically modify (SM) adhesives. This overall improved the adhesives bonding strength, toughness and water resistance. The coordination interactions between the polyurethane molecules and the protein molecules of SM were formed by multi-crosslinking via metal chelating, covalent bonding, and hydrogen bonding to enhance the adhesive's toughness, bonding strength and water resistance. As a result, the wet bond strength and toughness of the modified SM adhesives were 166.7 % and 275.3 % higher than blank sample, respectively, reaching 1.29 MPa and 0.61 J. Considering of the used raw materials and synthesis method in our process are simple and widely available, this study provides an eco-friendly and effective method for green, low-cost, and high-performance wood-based composite adhesives. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnesium oxychloride cement (MOC) has the advantages of no formaldehyde emission, fire resistant and curing at ambient temperature, which make it to be a promising wood adhesive for wood industry. However, the poor permeability of MOC on wood surface and the inherent brittleness of MOC limit its practical application. To solve these problems, citric acid (CA) and polyvinyl alcohol (PVA) fibers were demonstrated to synergistically promote the bulk penetration of MOC in wood surface and enhance the toughness of MOC, which resulted from the pH regulating effect of CA and the toughening effect of PVA fibers and CA. Based on this synergistic method, the compressive strength and toughness of the obtained MOC/CA/PVA adhesive were higher than that of pure MOC adhesive. Moreover, the wet adhesive strength of the MOC/CA/PVA adhesive reached 1.81 MPa, which increased by 33% than pure MOC adhesive. In addition, the wood products bonded by the modified adhesives possessed excellent flexural performance and fire resistance. This modification strategy makes the modified MOC-based wood adhesive have great application potential in wood and building industry. • Magnesium oxychloride cement was modified by citric acid and PVA fibers. • Citric acid and PVA fibers improved the water resistance and strength. • The enhanced mechanism was the chelation of CA and the filling effect. • The modified magnesium oxychloride cement has good adhesive strength. • The wood product bonded by modified adhesives has better flexural strength. [ABSTRACT FROM AUTHOR]

Faced with many challenges such as energy crisis and environmental protection issues, biomass soy protein-based adhesives for replacing aldehyde-based adhesives have gradually become one of the research hotspots for wood industry upgrading. However, soy protein-based adhesives still have many shortcomings. Low bonding strength, poor water resistance and high viscosity restrict their widespread industrial application. In this work, a modified soy protein isolate (SPI) based adhesive with strong water-resistant bonding strength and low viscosity was prepared. Oxidized sodium alginate (OSA) and calcium ions were employed in SPI adhesive system. Results showed that cross-linking between OSA, calcium ions and SPI occurred successfully. The mechanical properties of SPI were significantly improved. The dry and wet bond strengths were 2.05 MPa and 0.97 MPa, respectively, in 65.3 % and 49.2 % increments for comparison. The adhesive samples also showed a reduction in viscosity and an increase in thermal stability. It can be developed as a facile method for preparing bio-adhesives. [Display omitted] • Oxidized sodium alginate and Ca2+ were employed to modify SPI adhesive. • The adhesive shows high bond strength, good water resistance and viscosity. • The wet shear strength reaches 0.97 MPa. • Schiff bases reaction improves the cross-linking density of adhesive. • Hydrogen bonding network provides additional cohesion. [ABSTRACT FROM AUTHOR]

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. • A non-toxic and high-performance soybean protein-based adhesive was developed. • Microwave treatment (MT) breaks soybean protein molecule and exposes active groups. • After 4 mins MT, the wet shear strength of resultant plywood increased by 160.47%. • MT reduces the dosage of chemical reagent for soybean protein-based adhesive. • Relative cell viability of modified soybean protein-based adhesive reaches 204.41%. [ABSTRACT FROM AUTHOR]

As a renewable biomass resource, soy protein adhesives are a potential alternative to petroleum-based ones. However, synthesizing soy protein adhesives with excellent performance via a low-cost and facile strategy for practical application in the wood industry remains challenging. Herein, an innovative approach for fabricating a strong, tough, low-cost soy protein adhesive via dual cross-linked tailoring-making technology was proposed to impart multiple excellent performances. Specifically, the new strategy involved using calcium lignosulfonate (CLS), a residue from the pulping industry, as an anionic surfactant to untwist the spherical structure of soy protein, stretch the protein chains, and knit a reversible dynamic network structure with the protein chains and soybean polysaccharide molecules by multiple non-covalent interactions, and synergize with the robust cross-linked network of 1,6-hexanediol diglycidyl ether (HDE) to tailor the adhesive structure system. Notably, this design reflects the vital role of remolding the protein structural and soybean polysaccharide molecules network in optimizing the adhesive properties, including excellent bonding strength, anti-mildew, and flame retardancy performances. Therefore, this facile strategy can be explored to develop green and renewable protein adhesives for industrial wood applications. [Display omitted] • Eco-friendly adhesive was prepared by a dual cross-linked tailoring-making strategy. • Non-covalent and covalent linkages render adhesive robust network structure. • Multiple functions of adhesive were achieved successfully in a low-cost method. • This strategy could prepare adhesive using heat-temperature soybean meals. [ABSTRACT FROM AUTHOR]

Formaldehyde adhesive is the primary source of indoor formaldehyde pollution, posing a serious threat to human health. Soybean meal (SM), as an abundant biomacromolecule and co-product of soybean oil industry, emerges as a promising alternative to formaldehyde adhesive. However, the SM adhesive exhibits inferior water resistance and unsatisfactory bonding strength. In this study, a novel core–sheath structure with an inexpensive pulp cellulose core and a hyperbranched polymer sheath is synthesized and introduced into SM to develop a robust bio-based adhesive. Specifically, aldehyde-functionalized pulp cellulose is grafted with hyperbranched polyamide, which is terminated via epoxy groups, to synthesize a core–sheath hybrid (APC@HBPA-EP). The core–sheath APC@HBPA-EP serves as both a crosslinker and an enhancer. The results show that the wet shear strength of the modified SM adhesive exhibits a remarkable 520 % increase to 0.93 MPa, and its dry shear strength reaches 2.10 MPa, meeting the established indoor use standards. The Young's modulus of the modified SM adhesive shows a significant 282 % increase to 19.27 GPa. Additionally, the modified SM adhesive exhibited superior impact toughness (7.48 KJ/m2), which increased by 24 times compared with pure SM adhesive. This study provides a versatile strategy for developing robust protein adhesives, hydrogel patch, and composite coatings. [Display omitted] [ABSTRACT FROM AUTHOR]

Soybean protein adhesives are environmentally friendly biomass‐based aldehyde‐free adhesives that have good economic value for the wood industry; however, it remains challenging to produce soybean protein adhesives with excellent water resistance, toughness, and mildew resistance through a simple modification method. In this work, inspired by plant polyphenols, a novel crosslinked soybean meal adhesive (SMPT) is obtained using a facile economic method. Polyamidoamine‐epichlorohydrin (PAE) and tannic acid (TA) are combined with a soybean meal matrix to form a tough co‐crosslinked network through strong intermolecular forces (covalent bonds, ionic bonds, and hydrogen bonds) in adhesive system. The results show that the wet bonding strength of SMPT adhesives for plywood is 134.1% higher than the unmodified soybean meal adhesive. The adhesion properties met the standard requirements for interior‐use plywood. And the compact cross‐linking network structure is accelerated the greater energy dissipation, which improves the toughness of adhesive. Moreover, cationic azetidinium groups in PAE and phenol hydroxyl groups in TA synergistically not only exhibit the good antibacterial activities but also improve mildew resistance for SMPT adhesives. This facile strategy provides an economic sustainable method to prepare high‐performance environmentally friendly wood adhesives. [ABSTRACT FROM AUTHOR]

Crosslinking modification can effectively improve the water resistance of soy protein isolate (SPI) adhesive, but it often depends on petroleum‐based reagents, violating the concept of green environmental protection. Here, inspired by the breaking and recombination of the disulfide bond in the perm process, a high‐performance wood adhesive is prepared by incorporation of SPI (modified by sodium sulfite to cleave the disulfide bonds of protein chains) and feather keratin (FK, extracted from waste chicken feathers by breaking the disulfide bond) without using any other crosslinkers. The crosslinking reaction occurs by disulfide bonds derived from the sulfhydryl group of FK and SPI. Thus the wet shear strength of the SPI/FK‐20 adhesive is improved from 0.57 to 1.18 MPa, an increment of 107%. This study provides a green strategy to prepare high‐performance protein‐based adhesive from the waste products‐chicken feathers, which will contribute to the development of the environmentally friendly wood adhesive industry. [ABSTRACT FROM AUTHOR]

The exploitation of the environment-friendly and renewable biomass adhesive is a promising alternative compared to petroleum-based ones in the wood industry. In this study, soybean flour (SF) was chosen as a renewable starting material for the preparation of the biomass adhesive. The soy protein structure was unfolded by the calcium hydroxide and multiple reactive groups (-COOH, –NH 2 , –OH, –SH) of the protein chain were exposed. Inspired by the marine mussel protein, tannic acid (TA) with many poly-catechol/pyrogallol groups was capable of interacting with protein molecules under the alkaline conditions and the strong metal coordination between Ca2+ and TA enable to reinforce the network structure of adhesive. Furthermore, the incorporation of 1,6-Hexanediol diglycidyl ether (HDE) into the pristine protein adhesive had reacted with protein molecules via chemical covalent bonds to form the stable and toughness cross-linking network. The as-obtained adhesive showed improved bonding strength and comparable water resistance. Notably, the enhanced adhesive showed an outstanding wet shear strength of 1.12 MPa, meeting China's interior furnishing requirements (≥0.7 MPa). Additionally, in contrast to unmodified adhesive, the mildew resistance of the cooperation modified adhesive was improved and the storage life extended. This research provides a novel and green way to develop a formaldehyde-free adhesive for the wood industry. [Display omitted] • A renewable resource of soybean flour was used to prepare an eco-friendly adhesive. • The multiple interactions promoted to form a denser cross-linked network. • The bonding strength and water-resistance of adhesive were significantly improved. • The mildew resistance of protein adhesive was improved by the introduction of HDE. [ABSTRACT FROM AUTHOR]

Petroleum-derived formaldehyde resin adhesives are serious hazards to human health and depend on limited resources. Abundant, cheap and renewable biomass materials are expected to replace them. However, the contradictory mechanisms of high mechanical strength and fracture toughness affect the use of bioadhesives. Herein, a biomimetic soybean meal (SM) adhesive inspired by the structure of insect cuticles and shell pearl layer was proposed. Specifically, chitosan (CS@DA) modified 3,4-dihydroxybenzoic acid (DA, rich in catechol moiety) was anchored on molybdenum disulfide nanosheets (MoS 2) to construct a biomimetic structure with copper hydroxide and SM substrate (SM-MoS 2 /CS@DA-Cu). Schiff base, ionic, and hydrogen bonding strengthened the cohesion of the adhesive. The ordered alternating stacking "brick-mortar" structure stimulated the lamellar sliding and crack deflection of MoS 2 , synergistically reinforcing the toughness. Compared to SM adhesive (0.57 MPa and 0.148 J), the wet shear strength and adhesion work of the SM-MoS 2 /CS@DA-Cu were 1.68 MPa and 0.867 J, with 194.7 % and 485.8 % increases, respectively. The multiple antimicrobial effects of CS@DA, Schiff base, and Cu2+ increased the applicability period of the adhesive to 40 days. The adhesive also displayed favorable water resistance and flame retardancy. Therefore, this peculiar and efficient biomimetic structural design inspired the development of multi-functional composites. [ABSTRACT FROM AUTHOR]

Preparation of soybean meal adhesives offering good water resistance, prepressing adhesion as well as antimildew properties through a green and simple strategy remains challenging. In the present study, a self-assembled nanostructure-based filling enhancement strategy was proposed. Tannic acid (TA) is grafted onto the chitosan framework through free radical grafting, followed by ultrasound induced self-assembly into nanospheres. Chitosan based nanospheres (CS@TA) and ferric chloride (FeCl 3) complexing with nanospheres are combined to modify soybean meal (SM) based wood adhesives synergistically. CS@TA enables interaction with protein chains through hydrogen bonding and Schiff base reactions, which in combination with its nanostructure allows for a more homogeneous dispersion in the SM system. At the same time the Fe (III) ions chelate with the catechol, forming ionic bonds and obtaining a denser structure. The results showed that the dry and wet shear strength (DWSS) of SM/1,2,3-propanetriol triglycidyl ether (GTE) /5%CS@TA/Fe increased by 79% and 693% to 2.28 MPa and 1.27 MPa. At the same time, the residual rate (RD) increased by 9.3–72.5% and prepressing adhesion now reaches 0.71 MPa compared with SM adhesives. And CS@TA nanospheres as well as Fe (III) ions act on the cell membrane of bacteria to provide stronger antibacterial effect, the anti- mildew time has been extended from the initial 2 d to more than 15 d. The construction of multi-network reinforcement strategies through self-assembled nanostructures improves the application potential of SM adhesives and provides ideas for the reinforcement of other engineering materials. [Display omitted] • Self-assembled nanospheres chitosan-based prepared using free radical grafting combined with ultrasonic induction. • Preparation of environmentally friendly adhesives from processing residues soybean meal and biomass materials. • The adhesive has high bond strength, good water resistance and prepressing adhesion. • The anti-mildew of soy protein adhesive was enhanced and extends the storage life. [ABSTRACT FROM AUTHOR]

• A stable EDTA-TA synergistic system was constructed to enhance MOC composites. • EDTA can effectively aggregate 5-phase crystals. • The effect of the synergistic system on the crystallisation of hydration products was investigated. • The modified MOC composites have good water resistance and compressive strength. • MOC composites have excellent flame retardant properties and can be used in the wood industry. The high CO 2 emissions and instability of silicate cement binders during production and use have encouraged the development of low-carbon materials. In this study, an environmentally friendly and flame-retardant building material was produced from magnesium oxychloride cement (MOC) and wood. In practice, the considerable microcracking that forms during the hardening process makes MOC materials very sensitive to water, which limits their further use. Inspired by the predation of crabs, a simple and effective method was proposed to obtain better water resistance and mechanical strength of MOC composite by co-modifying with ethylenediaminetetraacetic acid (EDTA) or disodium ethylenediaminetetraacetic acid (EDTA-Na) in conjunction with tartaric acid. The four –COOH of EDTA and EDTA-Na coordinated well with the 5-phase structure and tightly aggregated the 5-phase crystals, effectively reducing the formation of microcracks. The synergistic effect between EDTA/EDTA-Na and tartaric acid prevented the disruption of 5-phase crystal structures by water molecules, thus improving the water resistance of the MOC composite. The softening coefficients of the MOC composite modified by EDTA and EDTA-Na in cooperation with tartaric acid after soaking for seven days were 0.97 and 0.98, respectively, which is significantly higher than that of the MOC composite modified by tartaric acid alone (0.54). At the same time, the co-modified MOC composite can be utilised as an inorganic adhesive for plywood, and the wet strength of plywood modified with EDTA in cooperation with tartaric acid being 25% higher than that of the unmodified MOC composite. In addition, the resulting composites showed great potential for application in low-carbon building materials, which can help alleviate the environmental impact of construction industries. [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 development of a water-retaining soybean flour-based adhesive with high water resistance, interfacial adhesion and mildew resistance is significant in replacing petroleum-based aldehyde-based resin. Drawing inspiration from lobster shells, soybean flour (SF), self-synthesized epoxy hyperbranched hydroxyethyl cellulose (EH) and calcium phosphate (CaP) oligomers were employed to prepare organic-inorganic hybrid composite adhesives based on hyperbranched structure. The EH component, abundant in active groups, enhanced the interfacial adhesion of the adhesives and served as an organic carrier for the mineralization of CaP oligomers. Prior to adhesive solidification, CaP oligomers mineralized to form an inorganic film akin to milk skin, which prevented water evaporation, resulting in a water retention time of 100 min for the adhesive. During adhesive curing, CaP oligomers with fluid-like behavior polymerized and mineralized, ultimately forming a continuous inorganic network of CaP crystals. This network, combined with the organic substrates (SF and EH), constituted an organic-inorganic hybrid structure, which bolstered the water and mildew resistance (20 days) of the adhesives. The prepressing intensity and wet shear strength of the resultant plywood increased by 168% and 396% to 0.67 MPa and 1.39 MPa, respectively, compared to those of the unmodified adhesive. The strength reached the leading level of the reported soybean flour adhesives. The biomimetic strategy employed here can be extended to high-performance gels and membrane materials, offering a novel modification approach for bio-composites. • Organic-inorganic hybrid composite adhesive based on hyperbranched structure was constructed. • Hyperbranched polymers enhanced interfacial adhesion and system compatibility. • CaP oligomers mineralized to form an inorganic film like milk skin to prevented water evaporation. • The adhesive has water retention, water resistance bonding performance and mildew resistance. • The strategy has significant reference for the research of gels, films and composites. [ABSTRACT FROM AUTHOR]

The preparation of plant protein-based adhesives is one of the potential strategies to mitigate environmental pollution. In this work, the organic-inorganic copolymerization of calcium phosphate oligomer and soy protein was performed by adopting the concept of organic-inorganic polymerization and the physics of polymer adsorption to eliminate the interphase boundary, preparing an adhesive layer with continuous and uniform network structure without using chemical cross-linkers. The participation of ionic and hydrogen bonds improved the mechanical strength. In addition, the Laponite with anisotropic charge distribution was introduced into the cross-linking network to increase the density and cohesion of cross-linking and further improve the bonding performance without complex chemical synthesis. The modified adhesive had an optimum wet shear strength of 1.01 MPa, and excellent water resistance (85.7 % residue rate). The modified adhesive shows good cell compatibility plus flame retardancy. Overall, this biomimetic study has excellent promises for the design of protein-based adhesives with desirable properties for engineering applications. • A soy protein adhesive was formulated by adopting organic-inorganic polymerization concept. • Using physics of polymer adsorption to eliminate the interphase boundary. • The modified adhesive has a wet shear strength of 1.01 MPa, and excellent water resistance. • The modified adhesive shows good cell compatibility plus flame retardancy. [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]

Magnesium oxychloride cement (MOC) adhesive has the advantages of being non-formaldehyde and flame retardant and having low energy consumption; however, its poor compatibility with the wood interface results in low bonding strength. Inspired by the H-bonded β-sheets nanoconfinement phase of spider silk, a high-performance inorganic adhesive was developed based on the supramolecular network system of poly (vinyl alcohol)/phytic acid (PVA/PA) with dissolved ions and the synchronous hydration process of MOC. Benefiting from the H-bond crosslinking and chelation confinement effects, the addition of PVA/PA enables MOC to penetrate steadily into the wood. Under this strategy, the compressive strength and softening coefficient of the modified MOC adhesive were 65.07 MPa and 0.84, which were 17.03% and 425% higher than the unmodified MOC adhesive, respectively. In addition, the MOC/PVA/PA adhesive achieved a wet shear strength of 2.02 MPa, 68.3% higher than that of the MOC adhesive. These results demonstrate that the MOC/PVA/PA adhesive would be a promising inorganic adhesive in wood-based building materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • ·A water-retaining structure is formed by constructing a topology and combining LiCl. • ·The water retention of prepared adhesive increased by 41% compared to unmodified one. • ·The adhesive shows good bond performance, 1.82 MPa for steel and 1.77 MPa for wood. • ·The adhesive can coat wet surface or low surface free energy substrates uniformly. 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. [ABSTRACT FROM AUTHOR]

The development of a water-retaining and high-bond-strength soybean flour (SF) adhesive is important to improve the efficient and clean preparation of plywood, promoting the substitution of aldehyde resin adhesives in the wood-based panel industry. Soybean protein isolate (SPI) was enriched on boron nitride (BN) to form protein-functionalized BN nanosheets (BS) with dense hydrogen bonds. Drawing inspiration from the strength and toughness of muscles, bionic structures based on BS and SF were designed to enhance adhesive bonding strength and toughness. A water-retaining agent epoxy hyperbranched polyester (EHP) was also synthesized to improve water retention and further enhance the bond strength of adhesives. Results show that the prepared adhesive with BS and EHP exhibits better initial viscosity and coating performance compared with unmodified SF adhesives. The prepressing intensity and wet shear strength of the prepared plywood increased by 227% and 400% to 0.72 and 1.05 MPa. In addition, EHP significantly improved the water retention of the adhesive from 0.5 h to 2 h. After 2 h, the wet shear strength decreased by 30.5% to 0.73 MPa, still meeting the interior use plywood requirement. Notably, this study provides a simple technique of water spraying to recover the dried adhesive layer, and the wet shear strength increased from 0.73 MPa to 0.87 MPa. This preparation strategy of biomass adhesive with water retention and low environmental load bear guiding significance for the efficient and clean production of the wood-based panel. • The prepared adhesives were inspired by the strength and toughness of muscles. • Dense hydrogen bonding enhanced strength and toughness of the adhesive. • Cross-linked structure improved water resistance of the adhesive. • A water-retaining agent was synthesized and improved water retention property. [ABSTRACT FROM AUTHOR]

[Display omitted] • An amphiphilic function is designed for developing biopolymer underwater adhesive. • The underwater phase transition of adhesive that triggered by solvent exchange is investigated. • Strong, stable, durable underwater adhesion is achieved based on a simple one-pot method. • This design is generic that can derive a family of superior underwater adhesives. Achieving strong and durable underwater adhesion in an easy way is highly demanded for practical applications. Despite extensive progresses, developing high-performance underwater adhesives by leveraging low-cost and sustainable biopolymer materials remains a hard task. Here, we report a simple one-pot strategy to construct a superior underwater adhesive through designing an amphiphilic function (established by thioctic acid and epoxy connector) in commercial biopolymer system. This amphiphilic-function-aiding biopolymer adhesive (AFBA), prepared in ethanol solution, can harness solvent exchange to trigger hydrophobic aggregation and phase transition in water, thereby yielding hydrophobic repulsion for effective dehydration, high structural stability for bulk cohesion strengthening, and versatile molecular interactions for interfacial adhesion enhancement. As such, AFBA exhibits a strong yet durable underwater adhesion (constantly increasing from 560 to 729 KPa to wood substrate after storing 30 days) and remarkable tolerance to various harsh environments (seawater, acidic, and alkaline solutions), allowing for underwater applying as a sealant to repair damage. Moreover, this simple strategy is generic that can derive a family of AFBAs with excellent underwater adhesion. This work may provide a promising pathway for engineering high-performance adhesives, and also open up a new direction to overcome the limitations of hydrophilic biopolymers in underwater application. [ABSTRACT FROM AUTHOR]

The adhesives formulated from soy protein (SP) exhibit desirable dry bonding strength needed to eradicate over-reliance on unsustainable petroleum-based formaldehyde adhesives. However, the adhesive full industrial adoption is limited by its inherent poor water resistance, short shelf-life, and proneness to mildew. This study explored a feasible, versatile, green, and sustainable strategy to engineer superior SP-based adhesives using furfuryl alcohol (FA) and 2,5-diamino-1,4-benzenedithiol hydrochloride (DBH). FA/DBH was conjugated via the carbodiimide-mediated addition of DBH under a light-proof condition. The acidity was controlled by NaOH, creating a mildly acidic medium for FA/DBH to develop a strong crosslinked network. The FA and DBH were hybridized by an amide bond, with subsequent SP integration via dynamic covalent linkages and amide bonds. The synergistic interactions between FA/DBH hybrid and the protein chains remarkably enhanced the adhesive properties. Consequently, the added FA/DBH hybrid (6 wt% of SP) achieved high dry and wet shear strengths of 2.38 and 1.43 MPa (plywood), which were 63 % and 200 % higher than the unmodified soy protein adhesive (USPA), respectively. In addition, the constructed organic network improved the adhesive thermal stability, mildew resistance, and shelf-life. Therefore, this sustainable, versatile, and green approach could serve as an alternative crosslinking pathway for developing highly competitive SP-based adhesives. [Display omitted] • A high-performance soybean protein adhesive was constructed without fossil resources. • A development strategy for covalently bonded furfuryl alcohol with sulfhydryl groups was proposed for the first time. • Soybean protein adhesive was crosslinked via dynamic covalent linkages and amide bonds. • The synergistic network enhanced the dry and wet shear strength of the resultant plywood by 63 % and 200 %, respectively. • The anti-mildew and shelf-life of the adhesive were remarkably invigorated. [ABSTRACT FROM AUTHOR]

In this study, a strong and multifunctional soy protein adhesive was designed and developed. It was then combined with wood units to prepare a clean and electromagnetic shielding wood-based panel via simple hot press. Specifically, bio-based raw material was prepared by grafting pyrrole (PY) and dopamine hydrochloride (DOPA) in sequence on to soy protein isolate (SPI), and then combined with AgNO 3 and a self-synthesized bio cross-linker epoxidized quercetin (EQC), to develop a strong and conductive soy protein-based adhesive with mildew-proof and flame-retardant properties. A covalent cross-linked structure and noncovalent bond (hydrogen bonds and ionic bonds) were formed among SPI, EQC, DOPA, and Ag+. As well, a hybrid structure was formed via in situ polymerization of Ag NPs, resulting in an adhesive with improved water resistance. Thus, the dry and wet shear strengths of plywood bonded with resultant adhesive increased by 78% and 52.4%, respectively, relative to those of the SPI adhesive. The modified adhesive exhibited good mildew resistance (shelf life ＞ 15 d) due to the natural antibacterial properties of quercetin, and the dynamic equilibrium of Ag NPs and Ag+ in the presence of DOPA. Meanwhile, the LOI of the modified adhesive was 41.3%, which is higher than that of SPI, improving flame retardancy of the resultant plywood. Notably, the obtained adhesive exhibited conductivity owing to the presence of polypyrrole (up to 7.09 S/cm), which can be used to develop reflection-based particle board with electromagnetic shielding ability. This study provides a high-potential and feasible strategy for developing multifunctional biomass composites to replace metal and polymer materials, which is an important and practical approach to promote sustainable development of materials and reduce carbon emissions. [Display omitted] • Pyrrole and dopamine were grafted on soy protein to obtain functional raw material (MSPI). • MSPI combined with epoxidized quercetin as a bio cross-linker and Ag+, to develop a wood adhesive. • The dry and wet shear strength of resultant plywood increased by 78% and 52.4%, respectively. • The resultant adhesive has antimildew property, flame retardancy, low environmental impact. • The resultant adhesive has conductivity and can be used to make electromagnetic shielding panel. [ABSTRACT FROM AUTHOR]

[Display omitted] • Enticing protein-based adhesive was constructed via dual crosslinking reactions. • Boron-coordinating dynamic covalently bonded network was synthesized with rich active sites. • Feather Keratin and boron-coordinated compounds simultaneously eliminate the adhesive hydrophilic groups. • The bonded plywood dry and wet tensile strengths increased by 72 and 186%, respectively. • The adhesive exhibit enhanced toughness, anti-mold ability, reduced viscosity, and low moisture uptake. In finding a potential long-term replacement for non-renewable formaldehyde materials, protein-based adhesive with plant resources as the main active ingredient has gained robust research interest. There is still an urgent need to alter the protein adhesive structural network and further invigorate its poor wet strength while eliminating the high mildew susceptibility. Herein, a green, sustainable, and versatile approach is reported to intensify the adhesive production technology through agricultural resources. The strategy explored a dual crosslinking process via sulfhydryl group recombination of chicken feather keratin (FK) and SP with boron coordinated 3,3′-dithiodipropionic and 2,2′-dithiodibenzoic acids (DTB hybrid). The dense network engineered strong adhesives through abundant dynamic covalent linkages. Owing to the enhanced cross-linking and organic hybrid system, the dry and wet tensile strength of the SPFK@DTB plywood increased remarkably by 72 and 186% (2.58 and 1.46 MPa, respectively) compared to the unmodified SP adhesive. The boron-coordinated hybrid system enriched the protein adhesive with enticing anti-mold properties, which preserves the adhesive bonding ability beyond 12 days. In addition, the formulated SPFK@DTB adhesives exhibited improved viscosity (16,181 mPa.s), thermal stability (above 200 °C), toughness, and reduced moisture uptake. This sustainable, facile, and versatile approach could accelerate the industrial mass adoption of SP adhesives. [ABSTRACT FROM AUTHOR]

Soybean meal (SM), as a byproduct of bean oil production, used to develop formaldehyde-free bio-adhesives to solve the formaldehyde release problem in the wood industry is very meaningful. However, the low water resistance and weak adhesion stability of SM-based adhesives limited their application and development. In this study, inspired by nacre and mussel byssus, a novel organic-inorganic hybrid system was formed by introducing Al(OH) 3 nanoparticles into SM adhesive. Al(OH) 3 nanoparticles interacted with SM to form dense noncovalent crosslinking network based on hydrogen and coordination bonds, enhancing the adhesion performance and water resistance of SM adhesive. The dry and wet shear strength of the SM/Al adhesive were improved to 1.75 MPa and 1.25 MPa, respectively. Meanwhile, the hydrogen and coordination bonds served as sacrificial bonds, which promoted dissipating energy and caused the toughness of SM/Al adhesive to improve by 133.3% to 11.2 MJ/m3. In addition, the dehydration process of Al(OH) 3 nanoparticles reduced the heat release of the adhesive combustion and improved adhesive flame retardancy. Therefore, the SM/Al adhesive showed a comprehensive improvement in adhesion strength, toughness, water resistance, and flame retardancy performances. This work provides a novel strategy for preparing strong, eco-friendly, multiple performances and low cost SM adhesives. A novel organic-inorganic hybrid wood adhesives were prepared using Soybean meal and Al(OH) 3 nanoparticles by imitating shells and mussel byssus. The bioinspired organic-inorganic hybrid structure endowed adhesive excellent strength, toughness and water resistance. Meanwhile, the introduction of inorganic phase Al(OH) 3 nanoparticles improved the adhesive's flame retardancy. [Display omitted] • A bio-inspired organic-inorganic hybrid soy adhesive was developed. • Low cost inorganic Al(OH) 3 nanoparticles partial replace chemical crosslink agent. • The bonding strength and water resistance of adhesive were improved. • The sacrificial noncovalent interactions enhanced the adhesive's toughness. • The flame retardancy of adhesive were improved. [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]

Plant based proteins are green, sustainable, and renewable materials that show the potential to replace traditional formaldehyde resin. High performance plywood adhesives exhibit high water resistance, strength, toughness, and desirable mildew resistance. Adding petrochemical-based crosslinkers is not economically viable or environmentally benign; this chemical crosslinking strategy makes the imparted high strength and toughness less attractive. Herein, a green approach based on natural organic-inorganic hybrid structure enhancement is proposed. The design of soybean meal-dialdehyde chitosan-amine modified halloysite nanotubes (SM-DACS-HNTs@N) adhesive with desirable strength and toughness enhanced by covalent bonding (Schiff base) crosslinking and toughened by surface-modified nanofillers is demonstrated. Consequently, the prepared adhesive showed a wet shear strength of 1.53 MPa and work of debonding of 389.7 mJ, which increased by 146.8 % and 276.5 %, respectively, due to the cross-linking effect of organic DACS and toughening effect of inorganic HNTs@N. The introduction of DACS and Schiff base generation enhanced the antimicrobial property of the adhesive and increased the mold resistance of the adhesive and plywood. In addition, the adhesive has good economic benefits. This research creates new opportunities for developing biomass composites with desirable performance. • A bio-based adhesive was prepared by an organic-inorganic enhancement strategy. • The organic-inorganic hybrid structure endowed the adhesive with high shear strength and water resistance. • The addition of dialdehyde chitosan and nano-filler enhanced the crosslink density and toughness of the adhesive. • The mold resistance and working life of the adhesive have been improved significantly. [ABSTRACT FROM AUTHOR]

The development of renewable soy protein (SP) adhesives has aroused growing interest in the wood industry. This research aims to develop a low-cost, sustainable, and high-performance SP adhesive without a petrochemical crosslinker. The hard skin barrier benefits from the dense cross-linked layer of cuticle cells constructed by the peptide bonds between membrane proteins and the dehydration condensation reaction between adjacent hydroxyl groups of polysaccharides. Inspired by the above skin mechanism, a biomimetic strategy of commercially available transglutaminase (TGase) was applied, which constructed Gln-Lys isopeptide bonds within the SP chains. The covalent boroxine structure formed by dehydration of the hydroxyl groups of boronic acid engineered a dense and robust network like skin barrier, converting the SP into a strong, water-resistant, anti-mildew, and flame-retardant adhesive. The resultant adhesive showed outstanding wet shear strength of 1.55 MPa, about 138.5% greater than the pure SP adhesive, and the residual rate increased from 86.19% to 95.99%. The small content of TGase achieved satisfactory performances and low-cost SP adhesive, establishing its usefulness as a crosslinker to replace the petroleum-based modifiers. Notably, the boronic acid mounted on the SP chains by TGase protected proteins from microbial consumption, thus extending the anti-mildew shelf-life of the liquid adhesives from 2 to 15 days. Moreover, the dense and rigid structure containing Gln-Lys isopeptide bonds and boroxine network effectively improved the flame resistance of the cured adhesives, which reduced the peak heat release rate (PHRR) from 95.1 to 84.2 W/g. Therefore, this simple bionic strategy achieved the goal of formulating green, low-cost, high-performance, and multifunctional SP-based adhesives. [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]

[Display omitted] • The interfacial bonding strategy of boron-nitrogen coordinated catechol-derived boronic ester was proposed. • The dynamic and stable covalent crosslinking network endowed the adhesive with excellent recyclability. • The wet shear strength and adhesion work of the adhesive were increased by 94.4% and 601.2%. • The adhesive exhibited remarkably improved mildew resistance and flame retardancy. Conventional covalent crosslinked protein adhesives are brittle and cannot be reprocessed effectively, which restricts their practical application and limits the recyclability of wood-based panels. Inspired by biological cartilage and mussels, a tough, strong, and recyclable soybean protein isolate (SPI)-based adhesive, SPI/BP@mica, was designed in this study by co-assembly of mica and SPI via dynamic boron-nitrogen (B-N) coordinated catechol-derived boronic ester (B-O) interfacial bonding. The dynamic covalent B-O, imine, and hydrogen bonds significantly improve the cohesive strength and energy dissipation capacity of SPI/BP@mica adhesive for high mechanical strength and toughness. The maximum wet shear strength and adhesion of SPI/BP@mica adhesive bonded plywood reach 1.05 MPa and 518.8 MJ, respectively, at increases of 94.4 % and 601.2 % over the original SPI adhesive. More importantly, we achieved a breakthrough in the recyclability of protein-based wood adhesives. Due to the synergistic triple dynamic mechanism and B-N coordination depolymerization of B-O bonds, second-generation particleboard prepared by recycling via hot-pressing and solvent-assisted repolymerization showed a rupture modulus of 12.1 MPa; to this effect, we fabricated a next-generation sustainable, reusable adhesive. The SPI/BP@mica adhesive showed excellent mold resistance (50-day shelf life) and flame retardancy (LOI = 29.7 %). Further, the cost of SPI/BP@mica adhesive is equivalent to the price of the phenol formaldehyde resin adhesive commonly used for wood-based panel. The proposed design strategy may promote the functional modification of composites and provide workable guidance for constructing robust, recyclable protein-based materials. [ABSTRACT FROM AUTHOR]

Biomass adhesives show great potential in developing environment-friendly wood-based panel industry. Among them, soybean protein isolate (SPI) adhesives have a wide source of raw materials, but exploring high-strength, water-resistant, mildew-proof soybean protein-based adhesives remains a tremendous challenge. Inspired by the spatial structure arrangement of spider silk in nature, a facile and efficient bionic approach is adopted to prepare soybean protein adhesive with excellent overall performance by introducing chitosan (CS) and MXene nanosheets in soybean protein. The addition of MXene nanosheets is expected to form the β-sheet crystalline conformation of spider silk, which contributes to the formation of a tightly cross-linked adhesive system that hinders the penetration of moisture. Compared with the 1-SPI adhesive, the prepared 5-SPI/CS/MXene adhesive shows an increase of 175% in wet shear strength (1.76 MPa), indicating excellent adhesion strength and water resistance. Besides, the addition of CS benefits to improve the dispersibility of MXene in the adhesive system. Therefore, the synergy of MXene and CS significantly improves the strength, water resistance of the adhesive and increases the storage time from 7 d to more than 50 d. This research would provide a new idea for the preparation of biomass-based adhesives. [Display omitted] • Aunique β-sheet structure of spider silk is constructed through simple method. • The prepared SPI/CS/MXene adhesive shows excellent wet shear strength (1.76 MPa). • Uniform dispersion of MXene in adhesive improves the toughness via load transfer. • The adhesive possesses excellent mildew resistance due to the CS and MXene. • The synergistic effect of CS and MXene optimizes the structure of the protein. [ABSTRACT FROM AUTHOR]

[Display omitted] • The BT@PDA@PANI hybrid filler was successfully constructed by rationally designed. • The resultant adhesive showed excellent water resistance and flame-retardant. • The EMI shielding material is absorption dominated and reveals 38.04 dB EMI. • The cost of EMI shielding material is significant reductions to 2165 RMB/m3. Resolving indoor electromagnetic interference (EMI) and radiation pollution caused by electromagnetic waves have become paramount. Plywood is broadly used in interior decoration and give them EMI shielding function will be significant for addressing these issues. Herein, inspired by the mussel underwater bonding strategy and oyster, polydopamine (PDA) graft transition layer was introduced between inorganic BaTiO 3 (BT) core layer and organic polyaniline (PANI) shell layer to construct controllable core@double-shell BT@PDA@PANI nanoparticles. The epoxide polymer and aldehyde-decorated carbon dots (CDs) were used as crosslinkers to form the covalent bonds and dynamic covalent bonds within the adhesive network. The core@double-shell nanoparticles were used as a reinforcing element and crosslinker to construct an organic–inorganic hybrid protein adhesive. This as-prepared protein adhesive exhibits remarkable improvements in wet shear strength (1.16 MPa), dry shear strength (1.97 MPa), and water resistance. Encouragingly, the plywood with in-situ formulated adhesives is an absorption dominated EMI shielding material and reveals an excellent EMI SE T of 38.04 dB EMI in the X-band, significantly outperforming most of the reported synthetic materials. This outstanding performance is attributable to its superior conductivity and unique hierarchical structure of plywood. Therefore, this study offers a facile, environmentally-friendly, and economically feasible strategy for preparing high-performance adhesives to address indoor EMI problems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A soy protein adhesive enhanced by two nanofillers was prepared. • The adhesive was cross-bonded with multiple covalent/non-covalent interactions. • The wet shear strength of the adhesive was increased by 160.7 %. • The nano-reinforcement and structural design strategy increased the adhesion force by 513.1 %. • The mold resistance of this adhesive was increased significantly. With the increasing attention to environmental concern, the reduction of fossil energy source and the demand of actual industrial production, there was strong demand to develop green, sustainable, and low-cost bio-based adhesive. Here, inspired by the self-assembly of nature to produce characteristic materials, multifunctional CA/TA/FC nanospheres were prepared from cinnamaldehyde (CA), tannic acid (TA), and ferric chloride (FC). Soybean meal (SM) adhesive was synergistically modified by nanospheres and sulfhydrylated nanotubes (HNTs@SH) through multiple networks and nanofilling strategies. The cross-linked network of the obtained SM-CA/TA/FC-HNTs@SH adhesive was reinforced by Schiff base reaction, acetal reaction, disulfide bonds (S S) generation/exchange, electrostatic interaction, ionic cross-linking, and hydrogen bond formation. Compared to SM adhesive, the dry/wet shear strength of the SM-CA/TA/FC-HNTs@SH adhesive was increased by 47.0 % (1.64–2.41 MPa) and 160.7 % (0.56–1.46 MPa), water resistance was increased by 9 % (68.1 %-77.1 %), viscosity was reduced to acceptable value (33.0 Pa·s), and effective storage time was extended by 50 days (d). Compared to currently used SM-PTGE adhesive, the cost was reduced by 26.7 % (2200 RMB/Ton), showing great potential as an alternative to the widely used formaldehyde resin adhesive. The combination of self-assembly, nano-filling, and multi-networking strategies also provided ideas for the enhancement and multi-functionalization of other engineering materials. [ABSTRACT FROM AUTHOR]

Natural materials show a special combination of remarkable strength and toughness. Therefore, inspired by nacre's "brick-and-mortar" architecture, high-performance multifunctional plant protein adhesives were constructed through an organic-inorganic hybrid structure and vitrimer networks. Hydroxyl-functionalized boron nitride (BN-OH) nanosheets firstly acted as the "brick" part, and protein chains were thought of as the "mortar" part. BN-OH can not only enhance the toughening through interlayer interface slip, but also achieves synergistic toughening effect with the nanometer effect. Glutaric dialdehyde (GD) acted as a "bridge" between protein chains and BN-OH, which can react with the condensation of hydroxyls in BN-OH or with active amino groups in protein chains to form dynamic covalent bond (vitrimer networks) to dissipate energy. Therefore, the synthesized multiple crosslinked network plant protein adhesives have excellent wet shear strength (1.28 MPa), water resistance, mildew-resistant, flame-retardant, and ultrahigh thermal management capability (3.88 W m−1 K−1), and has wide application potential in green adhesives. [Display omitted] • A high-performance plant protein adhesive was inspired by nacre design. • The BN-OH nanosheets were set as the "brick" part. • Plant protein chains were thought of as the "mortar" part. • Organic-inorganic hybrid and vitrimer networks enhanced the adhesive's strength. • Adhesive shows excellent mold resistance and thermal management capability. [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]

The substitution of environmentally friendly, renewable soybean-based adhesives (SBAs) for formaldehyde-based synthetic resins to produce formaldehyde-free wood composites is of great significance for resource recycling and environmental protection. However, SBA-bonded wood composites often exhibit great variations in bonding properties, due to the diverse interactions of the extractive components in wood. In this study, the extracts of four typical commercial fast-growing timbers were isolated, and their effects on the structures and properties of the SBAs were systematically investigated using FTIR, NMR, TGA, contact angle, buffer capacity, sol–gel test, and plywood evaluation. The analytical data indicated that some of the wood extracts could cause important effects on the bonding properties of the SBAs by impacting the PAE cross-linking capacity and unfolding degree of the globular soybean proteins. Fast-growing hardwood extracts from poplar and eucalyptus timbers containing active groups resulted in increased cross-linking density and improved water resistance of the SBAs. Meanwhile, fast-growing softwood extracts from Chinese fir and Scotch pine containing inert hydrophobic components had slight impacts on PAE cross-linking, but resulted in the agglomeration of unfolded soybean proteins. This formed a weak boundary layer on the wood surface, causing a significant decrease in the water resistance of the SBAs by >35%. These findings presented available analytic approaches of wood extract–SBA interactions and useful guidance for the proper applications of SBAs in the commercial production of wood composites. • The adhesion of soybean adhesive impacted by wood extracts was investigated. • The interactions of the wood extracts with the crosslinker PAE were characterized. • The interactions of wood extracts with soybean proteins were evaluated. • The structure–property changes of the soybean adhesives caused by the wood extracts were revealed. [ABSTRACT FROM AUTHOR]

Developing efficient and sustainable green adhesives to replace aldehyde-based adhesives has become an important strategy to address fossil resources depletion, environmental pollution, and clean production. Soy protein is a raw material-rich, renewable biomass material that can be used to prepare environmental-friendly adhesives. However, the weak interfacial adhesion of soy protein-based (SP) adhesives leads to poor coating and prepressing properties, thus limiting the large-scale application of the SP adhesives. In this study, a bionic "bond-stitch" molecular topology was designed and constructed in SP matrix to prepare a strong multifunctional adhesive. Inspiring by the strong adhesion of mussel, urushiol (U) with natural catechol structure and acrylamide were polymerized in situ into poly(urushiol- co -acrylamide) (PUAM) as stitching polymer, which was entangled with the SP network to form a bond-stitch molecular topology. The hydroxyapatite was used to construct an organic-inorganic hybridization in the SP matrix mimicking the tough cohesion of oysters. The resultant dual-bionic SP adhesive exhibited excellent coating performance, prepressing intensity (0.45 MPa), flame retardancy (the limiting oxygen index was 39.4%), mildew resistance (10 d), low volatile organic compounds release, and good antibacterial activity (the antibacterial rates against Escherichia coli , Staphylococcus aureus , and Candida albicans were 89.55%, 78.59%, and 99.91%, respectively.). The wet shear strength of the prepared SP adhesive was increased from 0.35 MPa to 1.17 MPa. This study provides a new strategy for the design and preparation of high-performance, sustainable, low-carbon footprint bio-adhesives and composites. [Display omitted] • Urushiol and acrylamide are polymerized into poly(urushiol- co -acrylamide) (PUAM). • PUAM forms a bond-stitch molecular topological structure in the adhesive matrix. • A dual-bionic adhesive with strong coating and prepressing properties is proposed. • The adhesive exhibits good antibacterial, flame-retardant, and mildew resistance. [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]

• A biomimetic brush-like polymer with a catechol structure (ADD) was designed and developed. • The Ca 3 (PO 4) 2 was deposited on soy flour and mixed with ADD to develop a biomineralized adhesive. • The dry and wet shear strength of resultant plywood increased by 118.8% and 750%, respectively. • The adhesive has outstanding coating performance, mildew resistance, flame retardancy. The development of a formaldehyde-free soy flour adhesive with good coating ability, mildew resistance, and flame retardancy while maintaining high bond strength, is urgent but presents a challenge. Inspired by the strong adhesive performance derived from the brush-like structure of gecko toes, a brush-like polymer with a catechol group was synthesized to improve the adhesive behavior of soy flour adhesives. Prompted by the high strength derived from the biomineralized structure of oysters, Ca 3 (PO 4) 2 was sedimented on soy protein and combined with the brush-like polymer to construct a biomineralized structure, which endowed the resultant adhesive with mildew resistance and flame retardancy while maintaining high bond strength. The dry and wet shear strengths of the bonded plywood by the resultant adhesive increased by 118.8 % and 750 % relative to those of the unmodified adhesive. Moreover, the resultant adhesive possessed outstanding coating performance, superior mildew resistance (no mildew for 7 d), and high toughness (4.05 J of the work of adhesion). The limiting oxygen index of the resultant adhesive was increased from 26.4 % to 30.1 %. Thus, developing a system combined with a bioinspired biomineralized strategy and a brush-like polymer can potentially offer a template for the fabrication of hydrogels, functionalized surfaces, and composite materials. [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]

Static electricity and formaldehyde pollution are not only severely harmful to ecological environment but also seriously affecting human health. It is of great importance but still challenging to develop an eco-friendly and multifunctional adhesive for electrostatic shielding. Protein adhesives were considered to be an effective substitute for formaldehyde resin adhesives, but show poor water resistance and conductive, limiting their practical applications in many fields, such as antistatic materials and antistatic floors. Therefore, this study aimed to develop a multifunctional adhesive by a facile organic-inorganic hybrid network to enhance the electrostatic shielding for antistatic materials. As we expected, the volume resistivity of the resultant adhesive for antistatic floors is only 2.73 × 108 Ω·cm, which is five orders of magnitude less than that of soybean meal (SM) adhesive and shows excellent electrostatic shielding performance. After experiencing a rapid thermal shock cycle between two extreme temperature conditions for 30 times, the mechanical performance of adhesive still remained stable. Furthermore, the adhesives are not only eco-friendly and non-formaldehyde, but excellent mildew resistance and flame retardancy. This multifunctional SM-based adhesive opens a new way to replace harmful formaldehyde-based adhesives, which have potential applications in the field of antistatic floors. • A high-performance adhesive was prepared by a facile and green organic-inorganic hybrid strategy for electrostatic shielding. • The multiple bonding structures were formed between protein chains and hydroxylated BT nanoparticles. • The adhesive exhibited mechanical stability under two extreme temperature cycling. • This adhesive could be used for antistatic materials with flame retardance and antimicrobial properties. [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]

For improving the water resistance, bonding performance, and anti-mildew property of the soy protein-based adhesive (SPA), in this research, based on cross-linking enhancement theory, soybean meal flour as the main raw material, self-synthesizing triglycidylamine (TGA), and larch tannin (LT) were used to build efficient crosslinking water-resistant structure and develop SPA. The effect of LT addition on the physical properties, bonding strength, and anti-mildew property of the resultant adhesive was investigated. The results showed that the residual rate of SPA with 4 % LT and 3 % TGA was improved by 2.1 % and the corresponding moisture absorption rate was reduced by 20.1 % compared with the SPA only modified by 3 % TGA. In addition, the SPA with 4 % LT and 3 % TGA had a 42.3 % increase in bonding strength, reaching 1.11 MPa, which satisfied the standard requirements of interior use plywood (≥ 0.7 MPa). The improved water-resistant bonding performance is mainly because interaction forces, such as hydrogen bonds, ionic bonds, and covalent bonds, formed between tannin and protein, and under the cross-linking effect of TGA, the whole cross-linking system forms a dense network structure. LT not only had a reinforcing effect on the SPA but also could prolong the pot life of the adhesive for 60 h due to the phenolic hydroxyl groups of tannin. Compared with the commercial anti-mildew agents, the mildew resistance before and after curing is the following: 1,2-benzisothiazole in-3-one > LT > sodium tetraborate > potassium sorbate. [Display omitted] • An easy-to-produce, high-performance, and environmentally friendly bio-adhesive was developed. • The incorporation of larch tannin enhanced the cohesion and mechanical properties of adhesives. • The resultant adhesive has better water-resistant bonding performance and an anti-mildew effect. • Effectively extend durability of plywood prepared by adhesive and storage period of the SPAs. [ABSTRACT FROM AUTHOR]

Developing eco-friendly soy protein-based adhesives instead of the extensively used aldehyde-based adhesives to fabricate wood-based panels can reduce environmental hazards and benefit human health. However, traditional soy protein-based adhesives lack long-term antibacterial and antimildew properties, reducing their bond strength and durability. Here, 3,4-dihydroxybenzaldehyde-grafted chitosan was prepared as a catechol structure donor and then introduced into the soy protein isolate (SPI) adhesive for the in situ reduction of silver ions to stable silver nanoparticles (Ag NPs); a biomineralization system was thus established. Notably, the catechol–quinone reversible redox reaction in the system endowed the resultant adhesive with excellent antibacterial (more than 99.99% bactericidal rate against Staphylococcus aureus and Escherichia coli , 91.67% bactericidal rate against Candida albicans) and long-term antimildew properties (40 d). The wet shear strength (1.24 MPa) and prepressing bond strength (0.80 MPa) of the plywood prepared with the adhesive were increased by 63.27% and 129.63%, respectively, relative to the SPI adhesive. The volatile organic compounds release of the adhesive was 1–2 orders of magnitude lower than that of commonly used commercial adhesives. This strategy provides inspiration for reinforcing antibacterial or antimildew bio-based adhesives, hydrogels, and composites. [Display omitted] • A system of biomineralized Ag NPs was built in the soy protein-based adhesive. • CS and SPI are used as stabilizers to avoid aggregation and agglomeration of Ag NPs. • The wet shear strength of plywood bonded by the adhesive was improved by 129.63%. • The adhesive has long-term antibacterial, mildew resistance, and low VOCs release. [ABSTRACT FROM AUTHOR]

Designing organic-inorganic nanohybrid systems have exhibited considerable potential in fabricating high-performance protein-based adhesives. However, the simplicity of the strategy, renewability, cost and effective dispersion of inorganic nanofillers in a hybrid framework remains challenging. This study proposed a simple, cost-effective, and sustainable design strategy to fabricate soybean meal (SM)-based hybrid adhesives using sodium lignosulfonate-functionalized graphene (SLS@G). SLS@G was simultaneously produced and functionalized via a dry ball milling method from graphite without using toxic reagents and tedious fabrication procedures. SLS@G had stable water dispersion and good compatibility with the SM adhesive matrix. The synergistic hydrogen bonding and hydrophobic interaction between SLS@G and the protein chains remarkedly improved the strength and water resistance of the SM-based adhesive. With minimal addition of the SLS@G (0.10 wt% of SM), the modified adhesive dry and wet shear strengths increased to 2.19 MPa and 1.15 MPa, which were 32.7% and 248.5% higher than the pristine adhesive, respectively. Moreover, the construction of the organic-inorganic nanohybrid structure also contributed to the thermal stability of the SM-based adhesives, leading to the increase in carbon residue rate from 26.6% to 28%. Overall, this facile and green strategy offers a new design pathway for developing advanced and multifunctional bio-adhesives for engineered wood-based composites. [Display omitted] • Functionalized graphene is produced via a green and low-cost ball-milling strategy. • A nanohybrid adhesive is prepared by introducing functionalized graphene. • Lignin helps improve the dispersity of graphene in the adhesive matrix. • Multiple interactions between functionalized graphene and the matrix are formed. • The interactions enhance the adhesion properties and toughness of the adhesive. [ABSTRACT FROM AUTHOR]