To replace the harmful adhesives used in wood construction, researchers from Aalto University in Finland have developed a bio-based adhesive composed of lignin.

Lignin — a structural component of wood and a by-product of the pulp industry — is being eyed as a replacement for current wood construction adhesives that contain formaldehyde, which is a colorless, potentially harmful gas featured in building materials like particleboard, plywood, and fiberboard; glues and adhesives; permanent-press fabrics; paper product coatings; and some insulation materials.

Source: Aalto UniversitySource: Aalto University

According to the Aalto team, lignin is the component that binds cellulose and hemicellulose together, giving wood its tough, strong structure. Because it is produced in substantial quantities in the pulp and bioprocessing industry, it is plentiful for other applications, including as an adhesive.

Aalto University researchers used purified kraft lignin in the making of the new adhesive and demonstrated that the chemical reaction to make the adhesive takes just a few minutes versus the 10 hours it takes to manufacture other adhesives. Further, additional heating of lignin is not needed as is the case with the materials used in the making of current adhesives, thereby reducing energy consumption.

The new adhesive, according to the researchers, contains 90% lignin versus previous lignin-based adhesives that feature just 20% to 50% lignin.

In addition to being a potentially healthier and more carbon-friendly alternative for adhesives used in the manufacture of wood construction materials, the adhesive is strong and non-toxic, and protects surfaces from fire, so it also shows promise as a flame retardant.

The article detailing the bio-based glue, Interfacial catalysis and lignin nanoparticles for strong fire- and water-resistant composite adhesives, appears in the journal Green Chemistry.

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