A new type of nontoxic wood glue

A new type of nontoxic wood glue made entirely from biological materials has been created by a team of international researchers. The new adhesive is described in a paper published in the American Chemical Society’s journal ACS Applied Materials & Interfaces.

Plywood is a handy building material used to make furniture and floors, among other things. It’s created by gluing thin layers of wood together and curing the resulting composite under heat and pressure.

A resin made from urea and formaldehyde is commonly used as the glue in plywood manufacturing. However, there are increasing concerns about the health impacts of the formaldehyde in composite wood products.

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Materials researchers have been investigating biologically based adhesives that could be used to replace the potentially hazardous glue. Previous studies have reported that a combination of sucrose (also known as table sugar) and citric acid (found in citrus fruits) can be used as a natural glue. However, this natural glue becomes weakened during the plywood curing process.

The authors of the new study, led by Hong Lei of Southwest Forestry University in China, tested an adhesive made of glucose and citric acid. Glucose is another type of natural sugar – in fact, it’s what all carbohydrates from our diet become when they are broken down by our bodies and absorbed into our cells.

A closeup photograph showing a cross-section of the plywood made with the new nontoxic woodglue
Three-layer plywood made with the new nontoxic wood glue. Credit: adapted from ACS Applied Materials & Interfaces 2022, DOI: 10.1021/acsami.2c02859.

After heating, the sticky glucose-citric acid solution was applied to sheets of poplar wood, which were then stacked and pressed together at 200°C for six minutes. In subsequent tests, the resulting plywood was shown to be strong and water-resistant.

The paper also reported that a higher citric acid to glucose ratio resulted in a higher adhesive strength.

“This green adhesive shows great potential to replace the existing industrial urea-formaldehyde resin adhesives,” the authors write.   

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