Wood Adhesives Based on Natural Resources: A Critical Review: Part I. Protein‐Based Adhesives

Dunky, Manfred

doi:10.1002/9781119846703.ch8

Cited by 17 publications

(7 citation statements)

References 279 publications

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“…Since wood is uneven and porous, adhesive wetting of wood is often poor, leaving voids in the adhesive layer. 42 Despite this challenge, we observed the adhesion is comparable to or even better than that of steel. This could be due to the lignin presence in wood, which acts as a natural glue between cellulose and hemicellulose and may also offer good adhesion in lap-shear testing.…”

Section: Resultsmentioning

confidence: 70%

Broad-spectrum lignin-based adhesives using thiol–silyl ether crosslinkers

Bension,

Zhang,

Menninger

et al. 2024

Polym. Chem.

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Section: Resultsmentioning

confidence: 70%

Broad-spectrum lignin-based adhesives using thiol–silyl ether crosslinkers

Bension,

Zhang,

Menninger

et al. 2024

Polym. Chem.

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“…On the other hand, it formed a highly cross-linked network through the cross-linking reaction, which enhanced the adhesive bonding strength of the adhesive. When excessive amino acids were added, some amino acids did not participate in the reaction, which increased the adhesive’s solid content and destroyed the cross-linking between the GER and amino acids [ 42 ]. The wet shear strength of S/G/L-9% was suitable for the selected ratios in this study, reaching 1.22 MPa.…”

Section: Resultsmentioning

confidence: 99%

Effects of Lysine on the Interfacial Bonding of Epoxy Resin Cross-Linked Soy-Based Wood Adhesive

et al. 2023

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Soy protein isolate (SPI) is an attractive natural material for preparing wood adhesives that has found broad application. However, poor mechanical properties and unfavorable water resistance of wood composites with SPI adhesive bonds limit its more extensive utilization. The combination of lysine (Lys) with a small molecular structure as a curing agent for modified soy-based wood adhesive allows Lys to penetrate wood pores easily and can result in better mechanical strength of soy protein-based composites, leading to the formation of strong chemical bonds between the amino acid and wood interface. Scanning electron microscopy (SEM) results showed that the degree of penetration of the S/G/L-9% adhesive into the wood was significantly increased, the voids, such as ducts of wood at the bonding interface, were filled, and the interfacial bonding ability of the plywood was enhanced. Compared with the pure SPI adhesive, the corresponding wood breakage rate was boosted to 84%. The wet shear strength of the modified SPI adhesive was 0.64 MPa. When Lys and glycerol epoxy resin (GER) were added, the wet shear strength of plywood prepared by the S/G/L-9% adhesive reached 1.22 MPa, which increased by 29.8% compared with only GER (0.94 MPa). Furthermore, the resultant SPI adhesive displayed excellent thermostability. Water resistance of S/G/L-9% adhesive was further enhanced with respect to pure SPI and S/GER adhesives through curing with 9% Lys. In addition, this work provides a new and feasible strategy for the development and application of manufacturing low-cost, and renewable biobased adhesives with excellent mechanical properties, a promising alternative to traditional formaldehyde-free adhesives in the wood industry.

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“…There is currently intense industrial interest in biobased adhesives for wood products, as they are considered environmentally friendly alternatives to petroleum-based adhesives. One of the potential biobased resources is soy flour, an agricultural byproduct of soy oil production that is renewable, non-toxic, low-cost, and abundantly available [ 1 , 2 , 3 ]. Soy-based adhesives have been used in plywood since 1923 [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

“…In the soy adhesive literature, it is commonly stated that denaturing proteins results in stronger bonds in wood because reactive groups are exposed [ 3 , 14 , 19 , 20 ]. In our experience, we usually observe cohesive failure in the adhesive rather than adhesion failure.…”

Section: Introductionmentioning

confidence: 99%

Effect of Protein Surface Hydrophobicity and Surface Amines on Soy Adhesive Strength

Kallakas,

Plaza,

Crooks

et al. 2024

Polymers

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Soy is considered one of the most promising natural materials for manufacturing wood adhesives due to its low cost, high protein content, and ready availability. However, more cost-effective ways of improving its wet shear strength are needed to achieve wider market acceptance. Protein adhesive wet strength depends on the use of (typically expensive) crosslinking additives as well as the processing/denaturation of the protein. It has been commonly stated in the literature that protein denaturation leads to higher bond strength by activating the surface and exposing the reactive groups. Therefore, we investigated how differences in surface reactive groups (surface hydrophobicity and reactive amine groups) brought on with different denaturation treatments relate to bonding performance. Fourteen soy protein isolates (SPIs) with different denaturation histories were investigated. Characterization of the SPIs included surface hydrophobicity, surface amine content, extent of protein hydrolysis, and bond strength (wet and dry, with and without polyamidoamine epichlorohydrin (PAE) crosslinking agent) by ASTM D7998. The molecular weight patterns showed that proteins denatured by extensive hydrolysis had very low bond strengths. Adding the crosslinker, PAE, improved all the shear strength values. We found that the number of water-accessible reactive amine groups on protein surfaces had no impact on the adhesive strength, even with the amine-reactive crosslinker, PAE. Conversely, increased surface hydrophobicity was beneficial to adhesive strength in all cases, though this correlation was only statistically significant for wet strength without PAE. While, in general, denatured proteins are typically thought to form better bonds than native state proteins, this work suggests that it matters how proteins are denatured, and what surfaces become exposed. Denaturation by hydrolysis did not improve bond strength, and extensive hydrolysis seemed highly detrimental. Moreover, exposing hydrophobic surface groups was beneficial, but exposing covalent bond-forming reactive amine groups was not.

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Wood Adhesives Based on Natural Resources: A Critical Review: Part I. Protein‐Based Adhesives

Cited by 17 publications

References 279 publications

Broad-spectrum lignin-based adhesives using thiol–silyl ether crosslinkers

Broad-spectrum lignin-based adhesives using thiol–silyl ether crosslinkers

Effects of Lysine on the Interfacial Bonding of Epoxy Resin Cross-Linked Soy-Based Wood Adhesive

Effect of Protein Surface Hydrophobicity and Surface Amines on Soy Adhesive Strength

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