A Single Cheap Chemical Lets Acrylic Glass Be Recycled at Half the Usual Temperature

Acrylic glass is everywhere, from window panes and furniture to car tail lights, and it is often sold under the brand name Plexiglas. Recycling it back into high-quality material has been difficult and energy-hungry. Now chemists at ETH Zurich have reported a method that could make it far easier: a single, inexpensive, commercially available chemical that unlocks the plastic's building blocks at roughly half the usual temperature.

The work, published in Nature Chemistry, comes from the group of materials scientist Professor Athina Anastasaki, with lead author Richard Whitfield, and chemistry professors Tae-Lim Choi and Gunnar Jeschke, who helped search for the right reagent. The team found that adding a single N-hydroxyimide compound to acrylic glass triggers depolymerisation, the breakdown of long polymer chains back into the original monomers. Once the reaction starts, it proceeds on its own, and it needs no solvents.

The numbers are striking. The breakdown begins at just over 200°C, whereas previous methods needed at least 400°C, and pyrolysis, used in other chemical recycling, typically runs above 400°C as well. The monomer yield can reach 98%, and the recovered monomers are very pure even when the starting acrylic contains dyes or impurities. By comparison, according to ETH, monomers from pyrolysis can contain impurities of up to 3%. The recovered building blocks can be used to make new acrylic of the same quality as the original.

"What makes our new approach so exciting is its simplicity," Whitfield said. Anastasaki added: "The only thing that surprised us was that a single chemical really was sufficient for the reaction." Because the process works with existing infrastructure and standard processes, companies would not need costly overhauls, and ETH reports that the chemical industry has already shown interest.

This is still a laboratory result. ETH Zurich has filed a patent application and is looking for licensees, and the team's next steps are to scale the method up, study the reaction in more detail and develop substances that speed it up and improve yields. The researchers also plan to apply the same principle to polystyrene, which, if it works, could widen the impact well beyond acrylic.