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By Alex Fox
Most plastics have a chemical history that makes starting a new life a challenge. The dyes and flame retardants that make them perfect for say, a couch cushion or a bottle of detergent, make them tough to transform into a desirable end product—one of the reasons just 10% of plastic in the United States gets recycled. Now, researchers have created a plastic with a special chemical bond that helps it separate out from those additives, turning it back into a pure, valuable product that can be re-used again and again.
To make the new material, researchers tweaked a type of vitrimer, a glasslike plastic developed in 2011, by adding molecules that change the chemical bonds holding it together. These new bonds, called dynamic covalent diketoenamine bonds, require less energy to break than those in traditional plastics.
As a result, the new plastic can be broken down into its constituent parts using just a solution of water and a strong acid at room temperature, the researchers report today in Nature Chemistry. The process doesn’t require a catalyst to set off the reaction, either, making it easy to collect high-quality recycled plastic from the resulting slurry. But the plastic isn’t at risk of falling apart ahead of schedule—researchers say the powerful acid required to break it down isn’t something most users are likely to encounter.
Traditional recycling methods produce dirty gray pellets (known as nurdles) that few manufacturers want to use, but this chemical recycling process creates plastic on par with brand new material. What’s more, the new method doesn’t require extra sorting. To demonstrate, the team mixed their material with shards of CD cases, plastic straws, and similar waste. Even in the presence of these other plastics, the new material’s molecules separated out.
The next big question is whether manufacturers will use it and recycling plants will accept it. Because the new plastic byproducts are more valuable—and because plants likely wouldn’t need a total overhaul to produce them, this sustainable plastic could soon catch on.
Source: Science Mag