Bio-based Wood Adhesives Research Articles

Waste sawdust as a raw material: Synthesis, modification and characterization of novel bio-based phenol-formaldehyde wood adhesives

Lignocellulosic biomass is a sustainable alternative to petroleum-derived chemicals for the development of bio-based wood adhesives. However, limited by the complexity and reactivity of biomass, bio-based adhesives are not competitive in terms of physicochemical properties. In this study, a novel bio-based phenol-formaldehyde resin was prepared directly using phenol to liquefy waste sawdust without removing the residue, and modified with a small amount of melamine. The results demonstrated that the melamine-modified bio-based phenol-formaldehyde resin (MBPF) exhibited better physicochemical qualities. Particularly, the free phenol content was 0.36 %, 57.6 % less than in common phenol-formaldehyde resin. Various characterizations of resins showed that liquefied sawdust could successfully substitute phenol in the resin system. Ortho hydroxymethylphenol was produced by an addition reaction between the liquefied sawdust or phenol and formaldehyde during the resin production process. A reticulated cross-linking structure was then formed between the hydroxymethylate liquefied sawdust and polyhydroxymethylphenol through the dehydrated condensation reaction. The degraded sawdust chain segments were successfully embedded in the resin, increased the molecular weight of the resin prepolymer and improved the initial thermal stability. After a tiny amount of melamine was added, the resin produced a denser cross-linked network, which improved resin condensation activity, decreased the curing time, and successfully increased the bonding force between the liquefied sawdust and resin molecules. The wet shear strength of MBPF resin could reach 1.43 MPa, which was equivalent to PF resin.

Mesoporous silica entrapped alpha-mangostin constructed tough, high strength, and mildew resistant soybean protein adhesives by organic–inorganic strategy

The production of value-added products from agricultural raw materials has been deemed a cutting-edge approach to attaining an uncontaminated geosphere globally. Thus, soybeans have recently attracted several wood-bonding capability studies due to their biobased, high-performance, and sustainable attributes. However, simultaneously achieving high-performance, mechanical, and anti-mildew properties in soybean protein (SBP) adhesive remains an enormous quest. Herein, an organic–inorganic strategy is reported to formulate SBP adhesive via adipic acid hydrazide strengthened α-mangostin (Sα-M) entrapped by mesoporous silica nanoparticles (MSN), yielding a highly biocompatible dense network (MSN/Sα-M). Afterward, the MSN/Sα-M was incorporated into SBP molecular chains through the enhanced dynamic covalent conjugation and intermolecular sacrificial hydrogen bonds to form SBP@MSN/Sα-M adhesive. Consequently, the multiple synergistic interactions resulted in tough adhesive layers, exhibiting high wood-bonding strength of 2.59 and 1.50 MPa at dry and wet conditions, increasing 66% and 206%, respectively. The SBP@MSN/Sα-M adhesive also offers excellent anti-mildew properties, with an extended wood bonding capability beyond 20 days of storage. This unique, versatile, and sustainable strategy provides new headway for developing bio-based wood adhesives from agricultural raw materials.

Production of Chemically Modified Bio-Based Wood Adhesive from Camote and Cassava Peels.

Adhesives are significant for manufacturing competent, light, and sturdy goods in various industries. Adhesives are an important part of the modern manufacturing landscape because of their versatility, cost-effectiveness, and ability to enhance product performance. Formaldehyde and polymeric diphenylmethane diisocyanate (PMDI) are conventional adhesives utilized in wood applications and have been classified as carcinogenic, toxic, and unsustainable. Given the adverse environmental and health effects associated with synthetic adhesives, there is a growing research interest aimed at developing environmentally friendly bio-based wood adhesives derived from renewable resources. This study aimed to extract starch from camote and cassava peels and focuses on the oxidization of starch derived from camote and cassava peels using sodium hypochlorite to create bio-based adhesives. The mean yield of starch extracted from camote and cassava peels was 13.19 ± 0.48% and 18.92 ± 0.15%, respectively, while the mean weight of the oxidized starches was 34.80 g and 45.34 g for camote and cassava, respectively. Various starch ratios sourced from camote and cassava peels were examined in the production of bio-based adhesives. The results indicate that the 40:60 camote to cassava ratio yielded the highest solid content, while the 80:20 ratio resulted in the best viscosity. Furthermore, the 40:60 ratio produced the most favorable particle board in terms of mechanical properties, density, thickness, swelling, and water absorption. Consequently, the starch extracted from camote and cassava peels holds promise as a potential source for bio-based adhesives following appropriate chemical modification.

Curing Behavior of Sucrose with p-Toluenesulfonic Acid.

With respect to the fossil resources shortage, the development of bio-based wood adhesives is an important research topic in wood science. There has been research on using sucrose for bio-based adhesives. However, a high acid catalyst content and a high hot-pressing temperature are required when manufacturing particleboards. In this study, to explore the possibility of p-toluenesulfonic acid (PTSA) as a promising acid catalyst for sucrose-based adhesives, the curing behavior of sucrose with PTSA (Suc-PTSA) was clarified. The thermal analysis results showed that the thermal properties of sucrose decreased significantly with the addition of PTSA. Based on the results of the insoluble matter rate, the optimal mixture ratio and heating conditions were determined to be 95:5 and 180 °C for 10 min, respectively. According to the results of FT-IR, the heat-treated Suc-PTSA contained furan compounds. In the context of the dynamic viscoelasticity, the onset temperature at which the storage modulus (E') begins to rise was significantly lower than those of the other sucrose-based adhesives. PTSA has the potential to cure sucrose more efficiently and at lower temperatures than previous sucrose-based adhesives, making it a promising acid catalyst for sucrose.

Effect of demethylation of acetone-soluble softwood kraft lignin on adhesion of lignin–phenol–formaldehyde resins

Owing to the increasing interest in sustainability and bio-based materials, softwood kraft lignin (SKL) was acetone-fractionated to reduce its heterogeneity and then demethylated to substitute phenol in lignin–phenol–formaldehyde (LPF) resins to be used as bio-based wood adhesives. This study investigated the effect of the demethylation of acetone-soluble SKL (AS-SKL) on the adhesion of LPF resins, where phenol was partially replaced with acetone-soluble demethylated kraft lignin (AS-DKL). Characterization of SKL, AS-KL, and AS-DKL using gel permeation chromatography (GPC), FTIR, and 31P NMR spectroscopy showed that the demethylation was successfully performed; the molecular weight (MW) and the number of methoxy groups decreased, and the number of –OH groups increased. The MW, chemical reactions, and curing behavior of LPF resins synthesized with different AS-DKL levels (10, 20, 30, and 50 wt%) were also characterized. With the increase in AS-DKL content, the viscosity and MW of the resin increased, whereas the gelation time decreased. LPF resins with 10% AS-DKL showed the highest tensile shear strength and lowest peak curing temperature. These results suggest that 10% is an optimal AS-DKL level in LPF resins for plywood bonding and that demethylation is an effective way of utilizing SKL.

Glycerol-based liquefied palm kernel shell product and its blend with citric acid as bio-based wood adhesive

Concerns for the environment and for human health have become critical factors that motivate creating bio-based wood adhesives. Therefore, this study proposes replacing toxic chemicals with alternative adhesives. In the first step, glycerol was added to the natural phenolic compounds from liquefaction of palm kernel shell (PKS), having a high content of lignin. The obtained glycerol-based liquefied PKS, and its blend with citric acid, were tested for bonding in a study on the effects of hot-pressing conditions (temperature and time). The results revealed that the liquefaction system in this study achieved an 83% conversion of the PKS components into glycerol-based liquefaction. According to the Fourier transform infrared and carbon-13 nuclear magnetic resonance analyses, the glycerol-based PKS contained lignin derivatives and furan products. This accounted for its great performance in bonding rubberwood veneers. The tensile shear strength was improved by blending with 15% citric acid, especially when applying the high 190 °C pressing temperature for 15 min.

Dual hydrogen-bonding network strategy enables fabrication of robust soy protein adhesive capable of excellent bonding at ambient temperature

The application of biobased soy protein adhesives is significantly limited by poor initial adhesion during assembly. This deficiency leads to weak interfacial adhesion and cohesion toughness attributed to insufficient intermolecular interactions. In this study, we propose a dual hydrogen bonding system within a waterborne epoxy emulsion (WEU), in which the 2-ureido-4[1 H]-pyrimidinone (UPy) moiety with quadruple hydrogen bonds is grafted onto an epoxy skeleton, and polyethylene glycol (PEG) blocks with regular weak hydrogen bond sites is used to emulsify the WEU by simple mixing. WEU then acts as a crosslinker to improve the mechanical performances of high-temperature soybean meal (HSM) wood adhesives. The introduction of UPy and PEG blocks contributes to the formation of a dense cohesion crosslinking network and an energy dissipation system via multiple hydrogen bonding with peptide chains, enhancing the cold-pressing bond strength of adhesives with a 140% increase, relative to that of a pure HSM adhesive. Thermocuring facilitates interfacial penetration and covalent links via an epoxy ring-opening reaction in the system, creating a secondary crosslinking platform to optimize the water resistance and toughness of the adhesives. Consequently, the cured HSMW-15 adhesive exhibits an improvement in wet bond strength from 0.11 MPa to 0.90 MPa, with optimal toughness at 2.74 MJ/m3. This effective and feasible design provides valuable insights into modification strategies for preparing biobased wood adhesives with superior performance.

Sucrose-tannin-nanosilica hybrid bio-adhesive based on dual dynamic Schiff base and disulfide bonds with enhanced toughness and cohesion

Herein, a high-performance sucrose-tannin bio-based adhesive is developed based on consisting of oxidized sucrose (OS), tannin acid (TA), SiO2 nanoparticles and 2,2′-disulfanediylbis (ethan-1-amine) (DBA) by a facile chemical cross-linking strategy. The OS-TA and OS-TA@SiO2 bio-based adhesives are characterized by XPS, FTIR, and 13C NMR, while the bonding performance is also investigated using shear strength test. Results show that the optimal formulation of OS-TA bio-based adhesive is a 2:1:1 mass ratio for OS: TA: DBA. When the mass fraction of SiO2 is 15 % and the solid content of main components is 50 %, the OS-TA@SiO2 bio-based adhesive has excellent bonding strength. Relative to OS-TA, the wet bonding strength of the OS-TA@SiO2 enhanced from 1.16 MPa to 1.85 MPa, while the dry bonding strength improved from 1.90 MPa to 2.50 MPa. The wood failure rate of the plywood fabricated by using the OS-TA@SiO2 bio-based adhesive reaches 80 %. Therefore, relying on the high flexibility of dynamic disulfide bonds, adding SiO2 nanoparticles into the adhesive system can facilitate greatly the mechanical interlocking effect and make the chemical cross-linking network more compact through the synergistic chemical interactions. This work provides new insights into producing green and renewable bio-based wood adhesives using sucrose and tannin.

Integration of branched amine and dialdehyde cellulose to produce high-performance bio-based wood adhesive

Rational design of environmentally friendly and sustainable bio-based wood adhesives is of great significance to people's health, environmental protection, high value-added utilization of crop resources and national economic development. In this work, we develop new cellulose-based wood adhesives and explore the differences in the spatial structure of branched polyamines and linear binary amines after cross-linking with dialdehyde cellulose (DAC). The bio-based wood adhesives DAC-2N (adhesives obtained from the reaction of DAC with diethylenetriamine) and DAC-3N (adhesives obtained from the reaction of DAC with tris(2-aminoethyl)amine) are prepared by the cross-linking reaction between DAC and linear amines (2 N)/branched amines (3 N). The effects of spatial cross-linking degree, mass ratio of amine to DAC and solid content of adhesives on the bonding performance are systematically studied, and the mechanical properties of wood specimens are also tested by universal mechanical tests. Results show that the best formulation of DAC adhesive is a 1:1 mass ratio of DAC to 3 N, and the optimal solid content is 40%. Compared with the pristine DAC adhesive, the dry bonding strength of the DAC-3N adhesive increased by 103% from 1.35 MPa to 2.74 MPa, and the wet bonding strength increased from 0 MPa to 1.81 MPa. DAC-3N adhesive with dense network structure has stronger glue and water-proof properties than DAC-2N adhesive, and the shear strength test of the three plywood shows the failure mode of the substrate rather than the failure mode of bonding or cohesion. Therefore, this study might offer a prospective strategy for future research, especially the rational design and potential application of bio-based adhesives with branched structure.

Development of biomass adhesives based on aminated cellulose and oxidized sucrose reinforced with epoxy functionalized wood interface

Both increasing environmental issues and the lack of fossil resources have increased the importance of wood-based natural fiber composites. Therefore, high performance, sustainable, and environmentally-friendly bio-based wood adhesives are highly desirable. We developed a new biomass adhesive based on aminated cellulose (AC) and oxidized sucrose (OS), and reinforced it with an activated wood interface to improve its bonding performance. To this end, the natural wood interface (NWI) was customized with an epoxy group to produce the epoxy-functionalized wood interface (EFWI), one end of which is tethered to the wood surface. The epoxy group at the other end reacts with the amino group of AC, resulting in hydrophobicity and forming new covalent bonds in the adhesive layer, such as -Si-O-Si-, -Si-O-C-, -C-N-C-, and -O-C-C- bonds. Characterization of the adhesive interface is realized by FTIR, 13C NMR, XPS, XRD, and SEM. Dry and wet shear strengths are also investigated by tensile shear strength measurements in China National Standards (GB/T 9846-2015). Results show that OS-AC adhesives have better dry and wet shear strengths at EFWI in comparison with those on NWI, reaching 2.52 and 1.48 MPa, respectively. Thus, the construction of a functionalized wood adhesive interface dramatically enhances the bonding strength and water resistance of biomass adhesives. This study provides new insights for developing renewable, low cost, and green bio-based wood adhesives by chemical modification of the wood interface.

Kraft Lignin Periodate Oxidation for Biobased Wood Panel Resins

The development of biobased resins with high-bonding performance has gained considerable attention in the wood industry. In this study, we developed biobased novolacs phenol-formaldehyde (BNPF) resins by partially replacing petroleum-based phenol and formaldehyde with lignin derived from kraft biorefinery and modified kraft biorefinery-derived lignin, respectively. We first performed a mild and efficient chemical modification of the lignin through the periodate oxidation process. Sodium periodate was used to oxidize the hydroxyl functional groups present in the interunit linkages (β-O-4 bond) in the lignin structure and convert lignin partly to quinones. This was assessed by Fourier-transform infrared spectroscopy, elemental analysis, solid-state 1H–13C 2D HETCOR NMR, and aldehyde content analysis. We synthesized a series of BNPF resins by replacing phenol with lignin, then by replacing formaldehyde with oxidized lignin, and finally by replacing both phenol and formaldehyde with lignin and oxidized lignin. The structural characterization results of the NPF resins revealed the formation of methylene linkages in the phenolic rings. Before application as wood adhesives, we studied the curing behavior of the formulated adhesive via differential scanning calorimetry. The adhesion strength of the adhesive was determined using the tensile shear strength analysis. The bonding performance tests indicated that BNPF resin adhesives have high adhesion strengths (>0.7 MPa). The outcome of this research provides a promising perspective to utilize natural polymers such as lignin for the synthesis of biobased wood adhesives.

Effect of Hemicellulose Molecular Weight on Bonding Properties in Biobased Wood Adhesives

Today, the most commonly used adhesives in the wood industry are fossil-based, but the search for new, renewable and less hazardous, resources for adhesives is intensifying. Hemicelluloses show promising bonding performance when used as a component in wood adhesives. Since batch-to-batch variations can affect the use of hemicelluloses in a large-scale production, we have investigated the effect of hemicellulose molecular weight on important adhesive properties, such as viscosity and bond strength, by using locust bean gum as a hemicellulose model and varying the molecular weight through hydrolysis. Results showed that there is a nonlinear proportionality between bond strength and molecular weight. In the molecular weight range used in the study, 70–1460 kDa, anoptimum in the adhesive performance was achieved with intermediate molecular weights, 320 and 530 kDa, especially when considering applicability and bond strength. Adhesives with lower molecular weights, 70 and 150 kDa, did not exhibit sufficient cohesive strength; therefore, the bond strength was lower. The adhesive with higher molecular weight, 1460 kDa, was difficult to apply, especially since its maximum solid content was very low, 5 wt %.

Latest advancements in high-performance bio-based wood adhesives: A critical review

Over the last 50 years, the use of wood adhesives in the manufacturing of wood-based panel goods has increased the efficiency of wood resources. Wood adhesives are becoming more popular as the need for wood-based panels grows. By 2028, the global market for wood adhesives is expected to reach 21.8 billion dollars. Even though urea-formaldehyde (UF), phenol-formaldehyde (PF), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), and resorcinol-formaldehyde (RF) resins are excellent in terms of bonding performance, workability, quality, and economy, they consist of harmful or toxic chemical agents derived from fossil resources, which make their application severely limited. This review aims to go through the most significant ‘green’ wood adhesives for manufacturing high-performance wood-based panels, such as lignin, tannin, protein, natural rubber, emulsion polymer isocyanate (EPI), 1C PUR polyurethane (for glue-laminated wood and cross-laminated timber), PMDI (for particleboards, medium-density and low-density fiberboards), carboxylic acid, and vegetable oil. The physical and mechanical characteristics of bio-based wood adhesives, as well as the development of sustainable, greener, and high-performance bio-based wood adhesives, are discussed in this work. Original research papers and review articles are among the most important sources since they provide complete information on the most recent developments in sustainable, eco-friendly, and high-performance bio-based wood adhesives.

H2O2-mediated tannin bio-based wood adhesive inspired by starfish structure and phenol-amine synergy

High-performance formaldehyde-free bio-based wood adhesives are extremely attractive because of the friendliness and sustainability of their ingredients and resources. This work reports a phenol-amine synergistic tannin bio-based adhesive inspired and designed by insect exoskeleton hardening and starfish structure. The phenol-amine synergistic strategy is based on Schiff base reaction and Michael addition between the benzoquinone group of tannin acid (TA) and the nucleophilic amino group of polyamines (PA XN , X = 4, 5 and 6, X represent the number of amino-terminal groups), which is supplemented by oxidation-induced quinone cross-linking in TA and the combination of covalent and non-covalent bonds. The proposed TAPA wood adhesives with the three-dimensional dense cross-linking network may dissipate stress via hiding sacrificial bonds, which can form a compact glue film to prevent the infiltration of water molecules as well as increase thermal resistance. FT-IR, XPS, and solid 13 C NMR demonstrated the tannin-based phenol-amine network was formed by cross-linking imine covalent bonds. DSC, TG, and DMA revealed reduced melting and glass transition temperatures, as well as improved thermal stability, which are conducive to the cross-linking and curing of adhesives. In detail, the dry lap shear strength of TAPA adhesive increased by 170% from 0.8 MPa to 2.16 MPa compared with pure TA adhesive by using poplar veneer as wood substrate; and the wet lap shear strength made a breakthrough from 0 to 1.06 MPa, exceeding the minimum requirement (0.7 MPa) defined by the China national standard (GB/T 17657–2013). Given this, a high-efficiency, green, and economic phenol-amine synergistic strategy are beneficial to the development of formaldehyde-free bio-based wood adhesives and multifunctional application of agricultural and forestry residues. Schematic illustration of developing phenol-amine synergetic TAPA wood adhesive inspired by insect exoskeleton hardening. • Tannin-based wood adhesives were prepared by phenol-amine synergy strategy. • FT-IR, XPS, 13C NMR, SEM, DSC, TG, and DMA characterization were carried. • Phenol-amine cross-linking network connected by covalent bonds and non-covalent bonds. • TAPA adhesives showed enhanced bonding strength, waterproof and thermal properties. • The formation of cross-linking network help to improve the performance.

Environmentally Friendly Starch-Based Adhesives for Bonding High-Performance Wood Composites: A Review

In recent years, bio-based wood adhesives have gained an increased industrial and research interest as an environmentally friendly and renewable alternative to the commercial petroleum-based synthetic adhesives used in the wood-based industry. Due to its renewability, abundance, relatively low price, and good adhesion properties, starch is a promising natural feedstock for synthesizing bio-based adhesives for wood-based composites. This review aims to summarize the recent advances in developing sustainable starch-based wood adhesives for manufacturing non-toxic, low-emission wood composites with enhanced properties and lower environmental impact. Recent developments in starch modification, physical, and enzymatic treatments applied to improve the performance of starch-based wood adhesives, mainly in terms of improving their water resistance and bonding strength, are also outlined and discussed.

Nanocellulose in Heterogeneous Water-Based Polymerization for Wood Adhesives

The interest in the development of biobased adhesives has increased due to environmental concerns. Moreover, as the production of engineered wood products (EWPs) is expected to grow, the wood adhesives market needs to transit toward formaldehyde-free products. Cellulose nanoparticles (CNPs) are a material with unique properties and advantages for producing hybrid materials as biobased wood adhesives. Besides their traditional use as reinforcing additives, CNPs can be incorporated at the beginning of the polymerization reaction to form in situ polymerized hybrid adhesives with better mechanical and physicochemical properties than the neat adhesive. Despite their outstanding characteristics, CNPs are still an emerging nanomaterial in the wood adhesive field, and the studies are incipient. This review explores the utilization of CNPs in heterogeneous polymerization for the production of polyvinyl acetate, polymeric isocyanates, waterborne polyurethane systems, and other waterborne polymer latexes. The main challenges are discussed, and some recommendations are set down for the manufacture of these novel hybrid nanocomposites.

Soy Protein Adhesives for Particleboard Production – A Review

Formaldehyde-based resins are commonly used in the particleboard industry due to their high bonding strength and excellent water resistance. Nowadays, the healthy and sustainable issues lead to the development of bio-based wood adhesives. In the last past decade, soybeans were the most prominent crop for the production of environmentally friendly adhesive with no formaldehyde in its composition. This review covers the strengths, weaknesses, opportunities and threats of soy-based adhesives as a replacement of conventional resins. Moreover, this work details the different techniques used to improve the performance of soy protein adhesives in order to encourage their use in the wood industry.

Biobased Epoxidized Starch Wood Adhesives: Effect of Amylopectin and Amylose Content on Adhesion Properties

Formaldehyde-free, water-resistant, and environmentally friendly wood adhesives were prepared from starches via a simple one-step epoxidation reaction followed by cross-linking using diethylenetriamine. This study focused on the effect of amylose/amylopectin ratio of starch (high amylose, low amylose, and amylopectin) on the epoxidation reaction and on the bonding performance of the prepared epoxidized starches. The epoxidation of starches altered the fluid behavior of the resins, from Newtonian for pristine epoxy to shear thinning, that corroborated the successful integration of starch chains as part of the epoxy resin. Epoxidized amylopectin had the highest viscosity, 114 Pa.s, and a high degree of substitution, 2.33 ± 0.10, among the starches that indicated that amylopectin is more favorable for the grafting of epoxy groups and for the integration of starch chains in epoxy resins compared to the starches with high amylose content. Bonding strengths were determined by lap shear tests on yellow birch specimens in dry, wet, and boiled conditions. High amylopectin epoxidized starch showed the highest lap shear bonding performance under wet conditions (5.50 ± 0.451 MPa). Under boiled conditions, all three epoxidized starches showed equally better performance than the unreacted starch-filled epoxy blends. This study provides fundamental insights into the effect of starch molecular structure on epoxidation reaction and adhesion properties and suggests a promising approach for developing strong formaldehyde-free sustainable biobased wood adhesives.

Comparison of the wood bonding performance of water- and alkali-soluble cottonseed protein fractions

The interests in biobased wood adhesives have been steadily increasing in recent years. Cottonseed protein isolate has shown potential as a renewable biobased adhesives. For a better understanding of the adhesive performance and mechanisms of cottonseed protein, we sequentially separated the isolated material into water-soluble (CSPw) and alkali-soluble (CSPa) fractions. The adhesive properties of both fractions on bonding maple wood veneers were tested at their natural pH (4.0 for CSPw and 7.0 for CSPa) and a common pH 11.0. The dry, wet, and soaked (i.e. wet and then re-dried) strength at break of the wood pairs bonded by CSPa were always higher than the values found for CSPw under the same conditions. Per the solubility and rheological analysis, the observed differences in bonding performance could be attributed to the fact that CSPw is more hydrophilic and lower in pI. ATR FTIR analysis was directly applied to the adhesive-coated surface area of maple strips cohesively broken by shear tests. Qualitative FTIR spectral features and quantitative contact angle measurement of the adhesive-coated maple surface evidenced the better wettability of cured CSPa than CSPw adhesives. Lesscarbohydrates leached out of CSPa during water soaking relative to CSPw. These observations increased the mechanistic knowledge of seed protein products functioning as wood adhesives, and would be helpful for the design and tuning of their future functional performance in green applications.

Dual-Network Nanocross-linking Strategy to Improve Bulk Mechanical and Water-Resistant Adhesion Properties of Biobased Wood Adhesives

Biomass-derived protein adhesives have gained considerable attention as a replacement for formaldehyde-based resins in industry. However, for biobased structural adhesives, water-tolerance polymeri...