Search

Starch-based wood adhesives are widely used as environmentally friendly and formaldehyde-free alternatives in the manufacturing of wood products. However, their poor water resistance and inability to inhibit bacterial/fungal growth limit their practicality. To address this issue, a physicochemical double-crosslinked network structure between citric acid, starch, and wood was prepared in this study by physically entangling the wood structure and chemically crosslinking the starch molecules, with citric acid preventing the activity of various enzymes and denatured proteins within microbial cells, thereby inhibiting bacterial and fungal growth. In water resistance cycling tests, the resulting esterified starch plywood demonstrated a 47.6 % and 13.2 % increase in water resistance compared with starch plywood and commercially available phenolic resin plywood, respectively. In addition, the tighter intermolecular bonding in the crosslinked structure results in a 31 % increase in heat resistance. The physical "nailing" and chemical crosslinking between the adhesive and the wood improved considerably the bonding strength to 98.36 %. The dual role of the physicochemical crosslinking of starch adhesives provides a straightforward strategy for the preparation of inexpensive, water-resistant, and fungal/bacterial-resistant starch adhesives, thus contributing to the promotion of starch adhesives., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Starch is a highly attractive carbohydrate in the production for the preparation of adhesives in recent years, due to its widespread availability, renewability, and abundance of reactive hydroxyl groups. However, the mechanical properties, hydrophobicity, self-adhesion, and particularly high energy efficiency are generally unsatisfactory for current starch-based adhesives. On this premise, starch was oxidized using Fenton's reagent in a ""one-pot cooking" process. The prepared oxidized starch was chain expanded by polyvinyl alcohol (PVA) and then cross-linked with a 10 % isocyanate (PM-200) to fabricate a starch-based adhesive (SFA) with a network crosslinked structure. SF 12 A 35% /2.5-55 adhesive shows significantly higher wet shear strength (1.18 MPa), a remarkable 94 % increase compared to SF 0 A 35% /2.5-55. The adhesive film also demonstrates both hydrophobicity (99° contact angle) and exceptional energy efficiency, with a DSC test revealing a notable 10 % elevation in energy efficiency. In addition, the crosslinked structure increases its molecular weight, thereby increasing its self-adhesion (Fig. S1). This study opens up new possibilities for the design and manufacture of multifunctional starch-based adhesives., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

In this paper, cassava starch was used as the main raw material to prepare high performance and environment-friendly starch-based adhesive. Starch was grafted with glycidyl methacrylate (GMA), and then cross-linked with sodium trimetaphosphate (STMP). Before preparation of plywood, polyaryl polymethylene isocyanate (PAPI) was mixed as chain extension agent. Prepared starch adhesives are used in wood-based panel applications. From the Fourier transform infrared (FTIR) analysis, it was found that GMA was successfully grafted to the starch adhesives which improved the hydrophobicity and shear strength of the adhesive. The plywood using modified starch adhesive at pH 4.50-5.50 showed the highest wet shear strength, 1.00 MPa, which was 163% higher than that using unmodified starch adhesive. The Scanning electron microscopy (SEM) results showed that the original morphology of starch particles were destroyed and became smaller during GMA grafting, which made the modified starch-based adhesive easier to penetrate into the bonding interface of plywood. The characterization results of the adhesive film also showed that the mechanical properties of the adhesive were better when the grafting reaction pH was 4.50-5.50. Graft copolymerization modification of starch improves the hydrophobic properties of starch binders., (Copyright © 2021. Published by Elsevier B.V.)

Starch-based adhesives were prepared by esterification modification with dodecenyl succinic anhydride (DDSA) and polyaryl polymethylene isocyanate (PAPI) as a crosslinking agent. DDSA modified starch (DMS) adhesives could significantly enhance the viscosity and adhesion strength of starch adhesives, making it beneficial to be applied in the field of plywood industry. This paper investigated the physicochemical properties of starch modified by dodecenyl succinic anhydride. Solid content, viscosity, adhesion, structural change and morphological features were characterized in detail. Viscosity and solid content of the modified starch (MF) adhesives was improved remarkably when DDSA was introduced. Three-ply plywood was fabricated with DMS adhesives, and its wet shear strength was measured. The results showed that the water resistance of the adhesive with 6wt% DDSA improved by 72.4% compared to that without DDSA. The wet shear strength plywood bonded by the adhesive reached 1MPa and could meet the requirement set by the China National Standard. Incorporating DDSA into the starch adhesive formed a dense crosslinking structure due to chemical reactions between DDSA and active groups on the starch molecules and thus improve the water resistance of the cured adhesives. The introduction of DDSA improving the viscosity and solid content remarkably, which increased the amount of the adhesive that penetrated the wood surface and formed more interlocks. Using DDSA promoted a smooth and homogeneous fracture surface of cured adhesive, which effectively prevented water intrusion and improved water resistance. The modified adhesive proved practical as a plywood adhesive for industrial application., (Copyright © 2018. Published by Elsevier B.V.)

A new biodegradable, renewable, and environmentally friendly starch-based wood adhesive that can be used at room temperature was synthesized by grafting of itaconic acid (IA) monomer onto cassava starch. When the addition of IA was 5% (starch basis), we can obtain the optimal mechanical properties of 15.38 MPa in dry state and 4.56 MPa in wet state. Compared with unmodified starch adhesive, the shear strength of grafted starch adhesive improved by 43.6% in dry state and 93.2% in wet state, respectively. The improved performance of the grafted starch-based wood adhesive was characterized by the measurement of viscosity and solid content, Fourier-transform infrared (FTIR), Thermogravimetry (TGA), X-ray diffraction (XRD) and scanning electron microscopy analyses (SEM). The results showed that there was a new characteristic peak of ester at 1700 cm−1 in the infrared spectrogram, which indicated the successful grafting of IA onto starch. After grafting modification, the storage stability and thermal stability of starch adhesive were improved. From SEM images and XRD patterns, we can witness that the morphology and crystallinity of starch particles were changed, which as a supplement of FTIR, confirmed the improvement of bonding strength and water resistance of the adhesive. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to obtain high-solids-content and low-viscosity starch adhesive, and improve bonding strength of the pure starch adhesive.Design/methodology/approach Maize starch was treated by hydrochloric acid solution with different concentrations, and acid-thinned starch adhesive was prepared. Polyisocyanate as a crosslinking agent was added to improve water resistance of the pure starch adhesive.Findings The physical and chemical properties of the acid-thinned starch adhesive were characterised. Acid hydrolysis did not change structure of starch granules, but increased its crystallinity. After acid modification, starch granules became less smooth and some fragments appeared. Acid treatment had little influence on thermal stability of starch, when acid hydrolysis was not strong. High concentration of HCl solution led to starch granules being destroyed, resulting in decrease in bonding strength. The optimal HCl concentration was 0.5 mol/L. Polyisocyanate addition was beneficial to improve the bonding strength of the acid-thinned starch adhesive.Research limitations/implications Acid hydrolysis changed the properties of the starch adhesive.Practical implications Acid hydrolysis decreased viscosity of the starch adhesive and improved its solids content, which had a positive effect on the application of the starch adhesive.Social implications It was helpful to develop an environment-friendly, natural polymer-based wood adhesive.Originality/value The properties of acid-thinned starch and acid-thinned starch adhesive were studied. [ABSTRACT FROM AUTHOR]

Utilizing corn starch as a main raw material to prepare starch adhesive, polyvinyl alcohol, borax, and carboxymethyl cellulose (CMC) were added in the preparation process. Because of the poor water resistance of native starch adhesive, an isocyanate prepolymer as a cross-linking agent was synthesized and added to improve its water resistance. Three-layer wood panels were fabricated and bonding strength was measured. The differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDX) were used to characterize the thermal properties, morphology, and element content of samples. Effects ofRvalue (the molar ratio of isocyanate group to hydroxyl group) and CMC addition on the physicochemical properties of starch adhesive were investigated. Thermal analysis results showed prepolymer/starch adhesive (PSA) cured at a relatively low temperature and thermal stability was improved after prepolymer added. SEM, XPS, and EDX results revealed that prepolymer played an effective role in bonding process, and the penetration of adhesive occurred in the wood, resulting in the improvement of bonding strength. [ABSTRACT FROM AUTHOR]

A Highly efficient method was developed for preparing starch-based wood adhesives with high performance, using H 2 O 2 , a silane coupling agent and an olefin monomer as an oxidant, cross-linking agent and comonomer, respectively. The effects of various parameters on the shear adhesive strength were investigated in the dry state (DS) and wet state (WS). The results indicated that the bonding strength of starch-based wood adhesives could reach 7.88 MPa in dry state and 4.09 MPa in wet state. The oxidation could reduce the content of the hydroxyl transforming into carboxyl and aldehyde groups, and the graft copolymerization enhanced the thermal stability, which improved the bonding strength and water resistance. The starch-based adhesive and the fractures in the bonded joints were analyzed via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The improved properties were attributed to the modified of microstructure of the graft-copolymerized starch-based adhesive. [ABSTRACT FROM AUTHOR]