New technology could make hard-to-recycle plastics recyclable
Cookware handles, electrical plugs, brake pads. Unlike other plastics, these ‘thermosets’ cannot simply be melted down and reshaped, making them difficult to recycle. Chemist Roxanne Kieltyka and her team are now exploring a way to make these materials recyclable, potentially transforming the way we handle plastic waste.
A material that is strong, heat-resistant, and durable. No wonder thermosets are widely used across all kinds of industries and applications. However, these same qualities also make them nearly impossible to recycle. ‘Thermosets are made up of tightly linked polymer chains that form a stable structure, resistant to heat and solvents,’ explains Roxanne Kieltyka from Leiden Institute of Chemistry. ‘Once they are set, they cannot be reshaped like regular plastics.’ As a result, most thermosets end up in landfills or are incinerated, contributing to pollution and wasting valuable resources.
Unlike traditional thermosets, which require extreme conditions to break down, this new material can be reprocessed in mild environments
A smart solution: dynamic bonds
To tackle this challenge, Kieltyka and PhD student Mertcan Özel are integrating into thermoset plastics squaramides—special chemical units that create dynamic bonds. ‘Squaramides can form and break bonds under the right conditions, meaning we can design plastics that are both strong and recyclable,’ says Özel. Unlike traditional thermosets, which require extreme conditions to break down, this new material can be reprocessed in mild environments, making recycling more practical and less energy-intensive.
How does it work?
Squaramides engage in strong and reversible hydrogen bonding. They can permit stiffening of materials while still being malleable. ‘What makes squaramides unique is their ability to show reversibility in their bonding configuration without the need for extra chemicals or catalysts,’ Özel explains. Instead of being discarded, old materials could be reshaped into new products with minimal waste and lower costs.
Testing for real-world use
To ensure these materials are ready for practical applications, Özel will be conducting a series of tests to optimise their synthesis. ‘We will look at how these plastics hold up over time, how they respond to heat and stress, and how effectively they can be reprocessed.’ By measuring factors like mechanical strength, thermal stability, and chemical resistance, he aims to fine-tune the material to balance performance and recyclability.
If successful, this approach could reduce plastic waste
A step toward a circular economy
This innovation aligns with the global shift toward a circular economy—where materials are reused rather than wasted. ‘Creating durable yet recyclable thermosets could reshape how industries think about plastics,’ Kieltyka notes. If successful, this approach could reduce plastic waste, lower greenhouse gas emissions, and make sustainable materials more accessible for a wide range of applications, from automotive parts to consumer goods.
The next steps involve synthesis of the materials, optimising their properties and testing them in real-world conditions. The team is also looking to collaborate with industry partners to guide them in their development towards application. ‘We are excited about the potential of this technology to make a real impact,’ says Kieltyka. ‘If we can bring this to market, it could be a game-changer for plastic recycling.’
Funding for new thermosets
NWO recently honoured Roxanne Kieltyka’s research project through the ENW-XS Open Competition for innovative research in the field of Exact and Natural Sciences