Scientists have created "recyclable endless plastic"

"The approach is innovative and elegantly simple," says an expert.

Plastic is a cheap and versatile material, so it is not surprising that it has become so widely used. The problem, of course, is that it is also very durable and is not easily recyclable, so it ends up largely as waste, causing considerable damage to the environment.

Research indicates that even biodegradable plastics are not environmentally friendly. The solution is then to stop using plastic products or at least to do it more economically.

Science can also help. A case in point: researchers at the Lawrence Berkeley National Laboratory of the US Department of Energy have developed a new form of plastic polymer that can be dismantled and reassembled with relative ease.

Plastics are composed of polymers, hydrogen and carbon chains, derived from substances such as oil. Their network of molecules can be mixed with a range of chemicals to achieve various properties, making plastics so versatile. Some plastics can be broken down into their components, making them easy to recycle. However, other plastics, such as thermoset polymers, are generally much harder to recycle.

"Most plastics have never been designed to be recycled," says Peter Christensen, a chemist at Berkeley's lab, author of a new study in the journal Nature Chemistry. "But we have discovered a new way to assemble plastics that takes into account recycling from a molecular point of view."

The lab team has succeeded in making durable thermoset polymers recyclable by tinkering with their monomeric components called diketoamine. They condensed these simple building blocks into newly created polydiketoenamine (PDK) bonds, which can easily be dissolved simply by soaking them in a strong acid bath for a few hours.

"It's a click reaction that works at room temperature, without the need for catalysts, additives, or even solvents," says team leader Brett Helms. "They just need a few minutes in a ball mill."

Once the polymers are broken down, the central parts can be separated from the additives several times in a closed-loop cycle, the researchers say. To test this recovery process, they contaminated PDK and acidic solutions with substances such as flame retardant chemicals because many plastics contain such additives. The scientists found that these additives did not significantly alter their recovery method.

This means that the end result is a plastic ingredient that is rid of its colors and chemical agents. It can therefore be reused in another product. "We are interested in the chemistry that redirects plastic lifecycles from linear to circular," says Helms. "We see an opportunity to make a difference when there is no recycling option."

"The approach is innovative and elegantly simple," says Rachel O'Reilly, a polymer science chemist at the University of Birmingham. "This new type of plastic can be recycled in a closed loop, which means that it can be depolymerized into its monomers," she adds, "and then transformed into a polymer with the same properties as it does." original".