Overview / Technology routes / Polycarboxylic acid systems
Ester-forming binders
Polycarboxylic acid systems
Citric acid with sucrose or other polyols forms ester crosslinks in the hot press without aldehydes.
Overview
Citric acid combined with sucrose, or used alone, bonds particleboard and plywood through esterification with the polyol and with wood hydroxyls. The approach was developed in Japan in the 2010s and has since been studied in many countries.
Chemistry and bonding mechanism
Heating forms anhydride intermediates from citric acid, which esterify hydroxyl groups. Sucrose partly dehydrates and caramelises under the same conditions. The resulting network is acidic and needs high press temperatures, around 200 °C in the original particleboard work.
Representative structures
Monomers and model units, drawn from SMILES with RDKit. Polymers are shown by a representative unit, not a full structure.
Citric acid
Tricarboxylic acid that forms ester crosslinks with polyols and wood hydroxyls on hot pressing.
OC(=O)CC(O)(CC(O)=O)C(O)=OSucrose
Polyol in citric acid-sucrose adhesives and sugar-based NIPU.
OC[C@H]1O[C@@](CO)(O[C@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@H]2O)[C@@H](O)[C@@H]1OPosition and maturity
- Typical products
- particleboard, plywood, binderless and low-binder boards
- Incumbent to beat
- UF for interior particleboard.
- Maturity
- Laboratory to pilot scale.
Strengths
- Simple, food-grade ingredients; no aldehyde involved.
What to watch
- Lower-temperature catalysts; board results under EN 312 at industrial press cycles.
Technical challenges
- High press temperature and long press time compared with UF.
- The acidity of the bond line can weaken wood and corrode equipment.
Cross-cutting: Water and moisture resistance · Press time, temperature and line throughput · Cost per qualified bond · Comparable life-cycle evidence
Quarterly track
2026-Q4 · Sept 2026 – Nov 2026
Machine-triaged leads (1)
Reaction-byproduct-enabled pore engineering in bio-based cork composites using a solvent-free epoxidized soybean oil-citric acid adhesive
The title describes reaction-byproduct-enabled pore engineering in bio-based cork composites using a solvent-free epoxidized soybean oil-citric acid adhesive.
2026-Q3 · Jun 2026 – Aug 2026
Machine-triaged leads (5)
A bio-based adhesive from sorbitol and citric acid for sustainable plywood manufacturing
A bio-based adhesive from sorbitol and citric acid is reported for sustainable plywood manufacturing.
Development of straw particleboard using citric acid as bio-based adhesive
Study develops straw particleboard bonded with citric acid as a bio-based adhesive.
Bonding Performance of Mildly Thermally Modified Petung Bamboo Using a Citric Acid-Based Adhesive
Study evaluates the bonding performance of mildly thermally modified Petung bamboo bonded with a citric acid-based adhesive.
In-situ citric acid modification of urea-formaldehyde adhesive with a low F/U molar ratio for improved plywood bonding performance
In-situ citric acid modification of urea-formaldehyde adhesive with a low F/U molar ratio was studied for plywood bonding performance.
“In-situ citric acid modification of urea-formaldehyde adhesive”
Water Resistance of Fully Bio-Based Particleboard Intended for Building Façade Application
High-density wheat straw, grey alder and softwood particleboards were bonded with birch-bark suberinic acids and tested for water resistance for façade use.
“the addition of birch-bark-derived suberinic acids (SAs) as the bio-based binder”
2026-Q2 · Mar 2026 – May 2026
Machine-triaged leads (5)
TERMITE RESISTANCE OF SAGO PARTICLE BOARD WITH CITRIC ACID-SUSCROSE ADHESIVE
Termite resistance of sago particleboard bonded with citric acid-sucrose adhesive is tested across layer compositions and acid-to-sucrose ratios.
“One of the ways of minimizing the use of synthetic adhesives is by using natural adhesives such as citric acid and sucrose”
Technical Feasibility of Citric Acid as a Bio-Adhesive for Production of Densified Laminated Veneer Lumber
Citric acid, alone and hybrid with MUF, bonded densified LVL panels from Pinus taeda veneers; all treatments exceeded EN 314-2 shear strength requirements.
“This study evaluated the technical feasibility of CA for producing densified LVL panels using wood from Brazilian Pinus taeda plantation trees.”
Valorization of fibrous sludge waste in eco-friendly particleboard production using citric-sucrose based bio-adhesives
Fibrous sludge waste was valorized in eco-friendly particleboard production using citric-sucrose based bio-adhesives.
Solvent- and Catalyst-Free In Situ Esterification of Citric Acid and Mannitol: Synergistically Enhancing the Dimensional Stability and Mechanical Strength of Poplar Wood
Citric acid and mannitol were esterified in situ in poplar wood, forming covalent ester bonds that improved dimensional stability and compressive strength.
“a solvent-free and catalyst-free method was used to synthesize bio-based polyesters from citric acid and mannitol”
Artificial intelligence-driven physical and mechanical properties of acid-based adhesive for manufacturing particleboard
Artificial intelligence was applied to the physical and mechanical properties of an acid-based adhesive used for manufacturing particleboard.
2026-Q1 · Dec 2025 – Feb 2026
Machine-triaged leads (9)
Candy Wood: Bioadhesive Based on Citric Acid and Glucose With Additives (Lignin, Starch and Glycerol)
Citric acid–glucose bioadhesives modified with lignin, starch or glycerol were characterized and tested in plywood panels; starch gave the best mechanical performance.
“bioadhesives formulated with citric acid and glucose, modified with lignin, starch, or glycerol”
Starch–Citric Acid Adhesive: Preparation and Performance Study Catalyzed by p-Toluenesulfonic Acid
p-Toluenesulfonic acid catalyzed starch–citric acid adhesive esterification, lowering hot-pressing temperature for plywood with good water resistance.
“The results demonstrate that pTSA substantially catalyzes the esterification crosslinking reaction between starch and citric acid.”
A simplified manufacturing technique of fabricating jute stick cross-banded board reinforced with citric acid as a natural binder: Process optimization and characterization
Cross-banded jute stick boards were made with citric acid as binder, optimizing acid concentration and pressing temperature, with ester linkages confirmed by FTIR.
“Fourier transform infrared spectroscopy analysis confirmed the formation of ester linkages between the carboxyl groups of CA and the hydroxyl groups of jute stick components”
Citric Acid as an Alternative Adhesive: Optimisation of Concentrations on Characteristics of Jabon Plywood
Study optimises citric acid concentrations as an alternative adhesive for Jabon plywood.
Characterization of Particleboard Form Sisal Using Citric Acid and Sucrose as Adhesive
Sisal particleboard bonded with citric acid and sucrose at varying ratios was characterized for physical and mechanical properties against JIS A 5908:2003.
“particleboard using sisal with an adhesive ratio of 15% citric acid and 85% sucrose has the best value”
Development of Suberinic Acids-Bonded Medium-Density Particleboard
Particleboard made from sawdust and recycled board residues bonded with a suberinic acid mixture from birch outer bark was tested for physical and mechanical properties.
“natural suberinic acids mixture obtained from birch outer bark as a binder”
A rapid-curing adhesive based on lactic acid and poly(vinyl alcohol) for plywood
A rapid-curing adhesive based on lactic acid and poly(vinyl alcohol) is reported for plywood.
Effects of heat treatment on environmental stability and dissolution behavior of citric acid-containing wood flour sheets
Wood flour sheets were wet-extruded with hydroxypropyl methylcellulose and citric acid, and heat treatment promoted crosslinking and water stability.
“heat treatment promoted CA-mediated crosslinking and insolubilization of HPMC within the sheet structure”
Life Cycle Assessment of Plywood Using Thermally Modified Birch Veneers Bonded with Suberinic Acids Adhesive
A cradle-to-grave life cycle assessment examined thermally modified birch plywood bonded with a birch bark-derived suberinic acids adhesive, finding bark extraction the dominant impact contributor.
“plywood manufactured from thermally modified birch veneers using the Thermovuoto® process, bonded with a birch bark–derived suberinic acids adhesive”
Key literature
- Umemura K., Sugihara O., Kawai S. (2013). Investigation of a new natural adhesive composed of citric acid and sucrose for particleboard. Journal of Wood Science. doi:10.1007/s10086-013-1326-6 research
- Sun S., Zhao Z., Umemura K. (2019). Further exploration of sucrose-citric acid adhesive: synthesis and application on plywood. Polymers. doi:10.3390/polym11111875 research
- Solt P., Konnerth J., Gindl-Altmutter W., Kantner W., Moser J., et al. (2019). Technological performance of formaldehyde-free adhesive alternatives for particleboard industry. International Journal of Adhesion and Adhesives. doi:10.1016/j.ijadhadh.2019.04.007 review