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A green and sustainable soybean flour (SF) adhesive is considered as a potential alternative to toxic formaldehyde‐based resins. Nevertheless, poor bond stability and low bonding strength is caused by the uneven size distribution and low reactivity of SF. Herein, SF adhesives with excellent and stable performance are synthesized via the synergistic action of high‐pressure homogenization (HPH) treatment by incorporating a green crosslinker. Specifically, an even distribution of the SF particles is obtained after the HPH treatment, from which large soy protein molecules are broken to several small and even single protein molecules. In this way, the adhesion stability is improved. Additionally, more active groups buried in proteins are exposed after the HPH treatment due to the unfolding of the protein molecules. Therefore, a more reactive SF is obtained and thus forms a denser crosslinking structure of resultant the adhesive, providing an increase in bonding strength. Particularly, the effects of homogenizing pressure on the adhesive performance are investigated. The results show that a 215.6% increase of wet bonding strength (1.01 MPa) is obtained after the HPH treatment with a homogenizing pressure of 20 MPa, meeting the standards (GB/T 9846‐2015) for interior applications. [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]

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]

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]

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]

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]

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] • 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 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]

[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 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 application of SM can improve the use of waste of agricultural industry. • The components of adhesive were derived from renewable waste or green resources. • Highly dense H-bonds and other interactions strengthened the adhesive network. • The wet shear strength of SM-based adhesive was improved by 105.2 %. • The adhesive exhibited good cytocompatibility and flame retardancy. 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. [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]