New lignin-based adhesive developed by university to replace formaldehyde adhesives

According to Science X, researchers at Aalto University have developed a bio-based adhesive that can replace formaldehyde-containing adhesives in wood construction.

The main raw material in the new adhesive is lignin, a structural component of wood and a by-product of the pulp industry that is usually burned after wood is processed. As an alternative to formaldehyde, lignin offers a healthier and more carbon-friendly way to use wood in construction.

Although timber construction has been touted as an environmentally friendlier method of construction as compared to using concrete or steel, the adhesives used to bond wood panels still contain formaldehyde, which can be harmful.

Instead, lignin, which comes from wood itself, binds cellulose and hemicellulose together and gives wood its tough, strong structure.

Previously, chemical-intensive pre-treatments have been necessary to use lignin in adhesives. The adhesive developed by Aalto University researchers can use purified kraft lignin and the chemical reaction to make the adhesive takes a few minutes instead of up to 10 hours.

Science X reports that no additional heating of the raw material is needed, which reduces energy consumption. The only by-products of the process are salt and sodium hydroxide, or lye.

“Using lignin as a material can reduce carbon dioxide emissions and increase the processing value of forests. This is why research on lignin is an important priority for us at Aalto University,” said Monika Österberg, professor at the Aalto University School of Chemical Engineering.

The lignin content of previous adhesives has been relatively low, around 20-50%, while the new Aalto University innovation has a lignin content of over 90%.

The adhesive is strong and non-toxic, and protects surfaces from fire, so it can even be used as a flame retardant.

According to the researchers, lignin can also be used as a raw material for applications such as coatings and composites. Research work will continue in the laboratory, and various commercialisation opportunities are likely to be explored in collaboration with LignoSphere, a spin-off from Aalto University.

Source: Science X