Scientists develop new eco-friendly glue of the future

By Gwyn Wright via SWNS

A new eco-friendly glue that can hold together home furniture, décor and floors has been developed by scientists.

Glues and resins that hold together chipboard, fiberboard and plywood normally contain pungent-smelling formaldehyde and could release this colorless gas into the air.

Fossil fuels used to make existing glues produce formaldehyde, which means the need for an environmentally friendly alternative has never been greater as the Earth warms.

Exposure to large amounts of the substance can also cause cancer but the links between the disease and smaller volumes of the gas are less clear, according to the American Cancer Society.

Researchers in China and France have now developed an alternative glue for plywood, which is used in many household objects, using sugar and citric acid, which is used to make orange juice.

To make plywood, manufacturers glue together thin layers of wood and then cure it under pressure and heat, creating large, flexible panels.

One of the most common glues is a resin made from formaldehyde and urea, which is found in urine, because it is cheap and bonds strongly to wood.

However, formaldehyde emissions from plywood with this type of resin could damage people’s health and the environment.

Earlier research has found a solution made up of sucrose, a sugar made from glucose and fructose, and citric acid can form a natural, water-resistant glue.

Zinc chloride is needed as a catalyst to reduce energy consumption while plywood is cured, which also reduces its’ strength.

The researchers wanted to find out if pure glucose and citric acid could produce a strong glue.

To make the new glue, researchers heated solutions of glucose and varying quantities of citric acid into a sticky liquid which they then applied to thin sheets of wood.

They then stacked three thin sheets of wood and pressed them into a single sheet at 200 degrees Celsius (392 degrees Fahrenheit).

The team cut the sheets into smaller pieces for strength tests and found that under pressures greater than 101 pounds per square inch, 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 were strong enough to satisfy the standard requirement.

The researchers say glues made from glucose and citric acid hold great promise for the future.

The study’s corresponding author Dr. Hong Lei said: “Adhesives (glues) play an essential role used in the fields of aerospace, electronic devices, architectures, furniture and packing industries.

“However, presently, a certain amount of adhesives are prepared by non-sustainable fossil sources, which produces volatile organic compounds (VOCs), such as formaldehyde.

“Formaldehyde-based resins, such as phenolic resin, urea-formaldehyde resin, and melamine-formaldehyde resin adhesives, are usually used to manufacture wood-based products, such as interior decoration materials and wooden furniture.

“The usage of formaldehyde-based resins inevitably leads to substantial formaldehyde emission concerns.

“Therefore, developing renewable, nontoxic, and biobased adhesives has been attracting much attention.

“As an environmentally-friendly catalyst-free adhesive, the prepared citric acid and glucose glue is a promising prospect.”

The findings were published in the journal ACS Applied Materials and Interfaces.