March 5, 2024

Chemists Develop a Non-Toxic Glue for Plywood – From Glucose and Citric Acid

Plywood and other composite wood products are utilized thoroughly in home decor, furnishings, and building and construction. They are frequently made utilizing glues and resins which contain potentially carcinogenic chemicals such as formaldehyde.
The go-to materials for building house furniture, décor, and floors are composite wood items that can be found in large sheets. However the glues and resins holding together particleboard, fiber board, and plywood typically include formaldehyde and could release this probable carcinogen into the air. To develop a non-toxic adhesive, researchers reporting today (May 11, 2022) in ACS Applied Materials & & Interfaces have actually combined glucose and citric acid– sugar and an orange juice component– into a strong, water-resistant wood glue for plywood.
To make plywood, manufacturers glue together thin layers of wood and after that treat the material under pressure and heat, producing large, versatile panels. Among the most popular adhesives to use in this application is a urea-formaldehyde resin due to the fact that its economical and bonds highly to wood. Formaldehyde emissions from plywood with this type of resin have raised health and environmental issues. Previous research studies have actually revealed that solutions of sucrose, a two-unit sugar made from glucose and fructose, and citric acid form a natural and water-resistant wood glue. However, a zinc chloride catalyst is needed to decrease the energy consumption for the plywood treating, which likewise decreases the adhesives strength. So, Hong Lei and colleagues wished to see if pure glucose and citric acid could create a strong adhesive with a less energy-intensive curing procedure.
Citric acid and glucose produce a wood glue that develops strong, waterproof three-layer plywood. Credit: Adapted from ACS Applied Materials & & Interfaces 2022, DOI: 10.1021/ acsami.2 c02859.
The scientists warmed solutions of glucose and differing quantities of citric acid into a sticky liquid that they used onto poplar veneers. Then they stacked 3 veneers and pushed them into a single sheet at 392 ° F( 200 ° C) for 6 minutes. The team cut the sheets into smaller pieces for strength tests and discovered that under pressures higher than 101 psi, the plywood samples all broke along the wood fibers and not at the glued seams.

To make plywood, manufacturers glue together thin layers of wood and then treat the product under pressure and heat, producing big, versatile panels. Previous studies have shown that options of sucrose, a two-unit sugar made of glucose and fructose, and citric acid form a natural and water-resistant wood glue. The team cut the sheets into smaller sized pieces for strength tests and found that under pressures greater than 101 psi, the plywood samples all broke along the wood fibers and not at the glued seams.

When the plywood samples were soaked in hot or boiling water, only the ones made with citric acid to glucose ratios above 0.6 had adhesive strengths that pleased the standard requirement.

These results please the standard requirement for plywood in China. When the plywood samples were taken in boiling or hot water, just the ones made with citric acid to glucose ratios above 0.6 had adhesive strengths that satisfied the basic requirement. The researchers associate these outcomes to the increase in ester links in between citric acid and wood, which increased the wood-binding strength and water-resistance.
Citric acid-glucose adhesives hold promise for the wood items industry, the researchers state.
Recommendation: “Fully biobased adhesive from glucose and citric acid for plywood with high efficiency” 11 May 2022, ACS Applied Materials & & Interfaces.DOI: 10.1021/ acsami.2 c02859.
The authors acknowledge funding from the National Natural Science Foundation of China, the Yunnan Provincial Natural Science Foundation, the 111 job and the French National Research Agency (ANR).