Once cured, thermosets are locked into a rigid structure that can’t be melted or reshaped, making them extremely durable. Unlike thermoplastics, which can be remelted and recycled, thermosets remain permanently ‘set’, contributing to the growing problem of plastic waste in landfills.
At the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2), Research Scientist Sheng Wang and Director Zibiao Li have been working on a solution. Together with collaborators at the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE); and the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, China; they developed a new generation of thermosets that maintain high-performance properties without sacrificing recyclability.
The key to their novel material, poly(α-cyanocinnamate) (PCC), lies in a specific chemical structure called Knoevenagel adducts. “The Knoevenagel reaction is a well-established method for forming C=C bonds with conjugated structures, while never used for the crosslinked polymers,” Wang and Li explained. “Such well-conjugated systems are suitable for preparing high performance thermosets.”
The team’s PCC thermoset was put through rigorous thermal, mechanical and chemical tests and delivered exciting results, matching the performance of conventional gold standard thermosets. The PCC achieved a Young’s modulus of 3.02–3.77 GPa, a tensile strength of 83–87 MPa, and an elongation at break of 6.8–8.8 percent. “These values show great prospects for application in plastic engineering” the researchers said.
Crucially, PCC can be recycled. The Knoevenagel reaction allows the polymer to be broken down, recovering one of its key building blocks, while the other component remains non-recyclable. This selective degradation means PCC can be recycled without contaminating other plastics, making it more viable for real-world recycling systems. The team also demonstrated the ability to recover valuable materials like carbon fibres from mixed waste streams, improving the overall sustainability of the process.
PCCs have the potential to transform industries—from automotive and electronics to aerospace—where high-performance thermosets are essential. Their ability to be reprocessed also makes them ideal for consumer goods such as sports equipment, appliances and recyclable packaging.
“We are now exploring new formulations and composites to expand the range of properties and functionalities of PCCs,” said Wang and Li, noting that they are also working on optimising recycling efficiency while minimising any performance loss over multiple cycles.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2) and the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE).
