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Catalytic disconnection of C–O bonds in epoxy resins and composites

Nature 2023 286 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Alexander Ahrens, Andreas Bonde, Hongwei Sun, Nina Kølln Wittig, Hans Christian D. Hammershøj, Gabriel M. F. Batista, Andreas Sommerfeldt, Simon Frølich, Henrik Birkedal, Troels Skrydstrup

Summary

Researchers developed a chemical recycling method using a ruthenium catalyst that can break down tough epoxy resins and recover their building blocks along with intact glass or carbon fibers from composites like wind turbine blades. This breakthrough addresses the plastic waste problem at its source by making it possible to recycle materials that currently end up in landfills, where they can fragment into microplastics.

Fibre-reinforced epoxy composites are well established in regard to load-bearing applications in the aerospace, automotive and wind power industries, owing to their light weight and high durability. These composites are based on thermoset resins embedding glass or carbon fibres1. In lieu of viable recycling strategies, end-of-use composite-based structures such as wind turbine blades are commonly landfilled1-4. Because of the negative environmental impact of plastic waste5,6, the need for circular economies of plastics has become more pressing7,8. However, recycling thermoset plastics is no trivial matter1-4. Here we report a transition-metal-catalysed protocol for recovery of the polymer building block bisphenol A and intact fibres from epoxy composites. A Ru-catalysed, dehydrogenation/bond, cleavage/reduction cascade disconnects the C(alkyl)-O bonds of the most common linkages of the polymer. We showcase the application of this methodology to relevant unmodified amine-cured epoxy resins as well as commercial composites, including the shell of a wind turbine blade. Our results demonstrate that chemical recycling approaches for thermoset epoxy resins and composites are achievable.

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