ETH Zurich researchers have pioneered a method to nearly completely recycle Plexiglas into its monomer building blocks, opening new possibilities for sustainable plastic use.
In a recent development for the world of materials science, ETH Zurich researchers have achieved what has long been considered nearly impossible — the complete breakdown of Plexiglas into its monomer building blocks. Their breakthrough promises to revolutionize the recycling of plastics, offering a sustainable alternative to the current practices that often result in incineration and environmental harm.
A team of scientists, spearheaded by Athina Anastasaki, an assistant professor in the Department of Materials at ETH Zurich, has discovered a method to break down Plexiglas, chemically known as polymethyl methacrylate (PMMA), into monomers.
These monomers can then be purified through simple distillation processes to create virgin-grade materials for new Plexiglas products.
A Simple and Robust Process
The innovative process involves dissolving Plexiglas in a chlorinated solvent and heating the mixture to temperatures between 90 degrees Celsius and 150 degrees Celsius while exposing it to UV or visible light. This triggers a depolymerization reaction facilitated by chlorine radicals released from the solvent.
“Our process is extremely simple,” Anastasaki said in a news release. “All we need is a chlorine-based solvent and to heat the dissolved recycling mixture to a temperature of between 90 and 150°C to start the depolymerization reaction with the aid of UV or visible light.”
What makes this discovery so remarkable is the simplicity and efficacy of the mechanism, even when dealing with long polymer chains and various additives that typically complicate recycling efforts.
The researchers tested the method on multicolored Plexiglas from the DIY market and still achieved yields of between 94% and 98%.
Significant Implications for the Plastic Industry
The potential impact of this breakthrough cannot be overstated. Plexiglas, with an annual global production of approximately 3.9 million tonnes, is widely used in various industries, including aerospace, automotive, electronics and construction.
Traditionally, plastics recycling has been limited and inefficient, often leading to the incineration of mixed plastics, which generates harmful emissions.
Until now, the only industrial method capable of breaking down similar polymer chains was pyrolysis, which involves thermal decomposition at around 400 degrees Celsius. Pyrolysis, however, produces a mixture of cleavage products that are economically inefficient to purify.
The ETH method sidesteps these limitations, offering a more energy-efficient and cleaner solution.
Towards a Sustainable Future
While the current method relies on a chlorinated solvent, Anastasaki’s team is already looking ahead.
“Chlorinated chemical compounds harm the environment. Our next goal is therefore to modify the reactions to enable them to work without the chlorinated solvent,” added Anastasaki.
Looking ahead, the ETH Zurich team’s work opens new avenues for recycling methods that target the breakdown of previously chemically inaccessible polymer chains. This could be a gamechanger in the ongoing battle against plastic waste, providing a more sustainable path forward.
Published in the journal Science, this development is a testament to the power of innovative research in addressing some of the most pressing environmental challenges of our time.
Source: ETH Zurich