Soy, casein, zein, gelatine and side-stream proteins; soy with PAE is the commercial reference.
Overview
Protein glues such as casein, blood and soy are among the oldest wood adhesives. Synthetic resins displaced them in the 20th century because of poor water resistance.
Soy flour crosslinked with polyamidoamine-epichlorohydrin (PAE) has been used commercially for interior hardwood plywood in North America since the mid-2000s. Research now targets other protein sources (zein, spent grain, rapeseed, insect and microbial proteins) and crosslinkers that do not need epichlorohydrin.
Chemistry and bonding mechanism
Proteins must be unfolded (denatured) so their polar and reactive groups can reach the wood surface. Typical treatments are alkali, urea, sodium dodecyl sulfate or enzymes.
Water resistance comes from crosslinking amine, carboxyl and hydroxyl groups. PAE azetidinium groups react with amines and carboxylates. Alternatives include epoxides, polyaldehydes, tannins and dopamine-inspired catechol chemistry.
Representative structures
Monomers and model units, drawn from SMILES with RDKit. Polymers are shown by a representative unit, not a full structure.
L-Lysine
Amine-rich amino acid; lysine residues in proteins and polylysine react with crosslinkers.
NCCCC[C@H](N)C(O)=O
Epichlorohydrin
Precursor of the azetidinium groups in PAE resins, the common crosslinker for soy adhesives.
ClCC1CO1
Position and maturity
Typical products
plywood, hardwood decorative panels, particleboard, finger joints and assembly
Incumbent to beat
UF for interior plywood and panels; PVAc for assembly bonding.
Maturity
Soy-PAE is commercial for interior plywood; most other proteins are laboratory to pilot scale.
Strengths
Many functional groups; good dry strength on veneer.
Uses side streams from food and feed processing.
What to watch
Brewing and distilling side streams moving to production batches.
Crosslinkers without epichlorohydrin, and wet-strength results under standard test methods.
Technical challenges
Wet strength and boil resistance usually depend on a crosslinker, which is often fossil-based.
High viscosity at useful solids content; short pot life; susceptibility to mould.
Soybean meal adhesive crosslinked with PAE, melamine-urea-glyoxal and blocked polyurethane reduced hot-pressing temperature and time for plywood bonding.
“The optimal SM/PAEc/MUG30/BPU5 adhesive exhibited a 12.5% lower hot-pressing temperature of 105 °C, a 20% shorter hot-pressing time of 4 min”
A formaldehyde-free soy protein, collagen and MDI adhesive containing a phosphorus-nitrogen-silicon flame retardant was prepared and tested on eucalyptus plywood.
“to fabricate a flame-retardant adhesive for eucalyptus plywood.”
machine-triagedresearch5 Oct 2026· ACS Applied Polymer Materials
Soy protein isolate adhesive crosslinked with a vanillin-derived trifunctional aldehyde and Fe@polydopamine showed higher dry and wet shear strength plus mold and flame resistance.
“the dry and wet shear strengths of the SPI-10TAM-5Fe@PDA adhesive reached 2.45 and 1.28 MPa”
machine-triagedresearchSept 2026· Chemical Engineering Journaltitle only
Soy protein adhesive was evaluated as a surface-layer modifier in pMDI-bonded bamboo particleboard, with the 2.2% pMDI plus 4% soy formulation showing the highest measured strengths.
“this study evaluated soy protein adhesive as a surface-layer modifier”
machine-triagedresearch21 Sept 2026· Journal of Composites Science
The Tribune reports that 40% of plywood units in Yamunanagar have adopted a urea-free resin input.
“40% plywood units in Yamunanagar adopt urea-free input”
2026-Q3 · Jun 2026 – Aug 2026
supplierconfidence: low10 Jul 2026·BindEthics
BindEthics moves Ecohesive to 40 L production batches
A July 10 company release says the brewing-waste adhesive has moved from laboratory testing to 40-litre production-grade batches, made with Chemique Adhesives, with initial batches earmarked for trials at European Tier 1 and eco-plywood manufacturers.
Editorial interpretation: a contract manufacturer and named trial route make this worth a sample request. The 2,000 L figure is a stated pathway and the 6,000 t figure is customer interest; neither is production.
Limitation: No recipe, solids, dosage, press cycle, panel test or independent qualification is published. "100% bio-based" and drop-in compatibility are supplier claims.
Route assigned editorially: the release names brewing by-products but does not disclose the binder chemistry.
Sourced facts (9) and gaps
Geography
UNITED KINGDOM LONDON, UNITED KINGDOM(Dateline, supplier)
Milestone
producing 40-litre production-grade batches progressing from laboratory testing to producing 40-litre production-grade batches(Paragraph 3, supplier)
Chemistry
100% bio-based, formaldehyde-free adhesive — basis: Supplier claim; not certified Ecohesive™ is a 100% bio-based, formaldehyde-free adhesive(Sustainable alternative section, supplier)
Renewable basis
by-products from the brewing industry — basis: Supplier-described feedstock; renewable fraction of the whole formulation not certified including by-products from the brewing industry(Sustainable alternative section, supplier)
Application
engineered wood applications developed specifically for engineered wood applications(Sustainable alternative section, supplier)
commencement of commercial customer trials commencement of commercial customer trials(Milestones list, supplier)
Capacity
2,000 — unit: litres per batch; basis: Supplier-stated pathway; not achieved; status: target; product: Ecohesive adhesive (per batch) a validated pathway to 2,000-litre manufacturing volumes(Paragraph 3, supplier)
Manufacturing
compatible with existing industrial mixing and pressing equipment — basis: Supplier claim; no press trial data compatible with existing industrial mixing and pressing equipment(Sustainable alternative section, supplier)
Next evidence to seek: Request batch records, product type, press cycle, dosage and independent (Bangor or third-party) EN test reports from the announced Tier 1 trials.
holdLignin-zein debondable plywood adhesive(24 Jun 2026, doi:10.1039/d6gc02129h) Author manuscript recovered, but veneer thickness (1.5 vs 1 mm) and dry spread (83 vs ~76 g/m²) differ between its sections; publisher version not yet compared.
holdCasein adhesive on beech compared with PVAc(16 Aug 2026, doi:10.3390/f17080972) Retained HTML was revised on 4 September, after the quarter cutoff; comparison withheld until the original August version is recovered.
Machine-triaged leads (7)
machine-triagedresearchJun 2026· European Polymer Journaltitle only
MXene-Ag nanostructures embedded in a soy protein isolate framework with 3-carboxyphenylboronic acid crosslinking yield a wood adhesive with reported dry and wet shear strengths.
“Replacing petroleum-derived wood adhesives with soy protein isolate (SPI) offers a sustainable alternative”
machine-triagedresearchJun 2026· International Journal of Adhesion and Adhesivestitle only
The study compares PVAc with bone glue, fish glue and casein adhesives for bonding European beech wood under ambient conditions and moderate thermal exposure.
“PVAc exhibited the most consistent bonding performance, whereas casein achieved shear strength comparable to that of PVAc”
machine-triagedother21 Aug 2026· Woodworking Network
Laccase-oxidized waxberry tannin blended with soybean meal formed a quinone-amine crosslinked network; plywood bonded with the adhesive reached 0.85 MPa wet shear strength at 63 °C.
“plywood bonded with OTS exhibited a wet shear strength of 0.85 MPa at 63 °C”
machine-triagedresearchMar 2026· International Journal of Adhesion and Adhesivestitle only
The paper reports preparation of a water-resistant gelatin-based wood adhesive through synergistic supramolecular preassembly and covalent cross-linking.
machine-triagedresearchApr 2026· Industrial Crops and Productstitle only
Environmental storage conditions induced variations in the mechanical strength of soy protein-based adhesive-bonded plywood, and underlying mechanisms were studied.
“Environmental storage conditions-induced variations in the mechanical strength of soy protein-based adhesive-bonded plywood”
machine-triagedresearch11 May 2026· Drewno. Prace Naukowe, Doniesienia, Komunikaty = Wood. Research Papers, Reports, Announcements
The study presents an enzymatic hydrolysis-assisted protein adhesive integrated with polyamide-polyurethane resin with enhanced strength and toughness.
machine-triagedresearchMay 2026· Journal of Cleaner Productiontitle only
Phenol-glyoxal precondensate was used as a crosslinking agent in a soy protein adhesive, and plywood hot-pressing parameters were optimized by orthogonal experiments.
“this study employed a phenol-glyoxal precondensate as a crosslinking agent and optimized the hot-pressing process parameters for plywood”
machine-triagedresearch8 Dec 2025· Wood Material Science & Engineeringtitle only
Wood sawdust, soy protein isolate and glutaraldehyde composites were prepared and characterised; imine formation between GTA carbonyls and SPI amines was related to mechanical property changes.
“It was established that chemical interactions occur between GTA carbonyl groups and SPI primary amine groups”
Key literature
Dunky M. (2020). Wood adhesives based on natural resources: a critical review Part I. Protein-based adhesives. Reviews of Adhesion and Adhesives. doi:10.7569/raa.2020.097309review
Vnučec D., Kutnar A., Goršek A. (2016). Soy-based adhesives for wood-bonding – a review. Journal of Adhesion Science and Technology. doi:10.1080/01694243.2016.1237278review
Kumar R., Choudhary V., Mishra S., Varma I.K., Mattiason B. (2002). Adhesives and plastics based on soy protein products. Industrial Crops and Products. doi:10.1016/S0926-6690(02)00007-9review
Liu Y., Li K. (2007). Development and characterization of adhesives from soy protein for bonding wood. International Journal of Adhesion and Adhesives. doi:10.1016/j.ijadhadh.2005.12.004research
Huang J., Li K. (2007). A new soy flour-based adhesive for making interior type II plywood. Journal of the American Oil Chemists' Society. doi:10.1007/s11746-007-1162-1research
Gui C., Wang G., Wu D., Zhu J., Liu X. (2013). Synthesis of a bio-based polyamidoamine-epichlorohydrin resin and its application for soy-based adhesives. International Journal of Adhesion and Adhesives. doi:10.1016/j.ijadhadh.2013.03.011research