Scientists at ETH Zurich in Switzerland have developed a chemical recycling method that can break down acrylic glass or PMMA, into its original monomer at temperatures below 200°C.
PMMA is widely used in products such as plexiglass and Perspex because it is lightweight and resistant to shattering. However, conventional recycling methods generally require temperatures above 400°C and may use solvents, making the process more energy-intensive and potentially affecting the quality of the recovered material.
The new technique uses a chemical reaction involving an N-hydroxyimide reagent to split the PMMA polymer chain. One of the resulting fragments can then rapidly break down into its monomer which can be used to produce new acrylic material.
In laboratory experiments, the process achieved a recycling yield of up to 96% at temperatures between 180°C and 230°C. When the remaining material was subjected to a second recycling cycle, the overall recovery reached 99%.
Researchers said the method works directly on commercially relevant PMMA and does not require solvents or light irradiation. This could simplify the process compared with some earlier approaches based on specially modified plastics or photochemical reactions.
The researchers have filed a patent and are now investigating ways to scale up the technology and identify cheaper chemical reagents. However, they noted that further work is needed before the method can be considered for commercial-scale recycling.