The chemical process disassembles epoxy composite, releasing intact glass fibres and extracting one of the chemical component of the resin.
Both are as good as new materials, according to the university, which added that the process could also be used with some materials that are reinforced with carbon fibres: “The newly-discovered process is a proof-of-concept of a recycling strategy that can be applied to the vast majority of both existing wind turbine blades and those presently in production, as well as other epoxy-based materials.”
A ruthenium-based catalyst and two common solvents – isopropanol and toluene – are used. The extracted polymer building block is bisphenol A, known as ‘BPA’.
The method as it is is not scalable as it need too much catalyst to be practical, and ruthenium is too expensive, pointed out the university, which is working on improvements. That said, it did ready ~70% of the mass of the composite for reuse.
“We see it as a significant breakthrough for the development of durable technologies that can create a circular economy for epoxy-based materials,” said project chemist Professor Troels Skrydstrup. “This is the first publication of a chemical process that can selectively disassemble an epoxy composite and isolate one of the most important building blocks of the epoxy polymer as well as the glass or carbon fibres without damaging the latter in the process.”
Aarhus University worked with Vestas, Olin and the Danish Technological Institute. Together they have formed the CETEC (circular economy for thermosets epoxy composites) project. A patent application has been made for the demonstration process.
The work is covered in the Nature paper ‘Catalytic disconnection of C-O bonds in epoxy resins and composites‘, which is clearly written, even for the non-chemist, and can be read in full without payment.