Fibre-reinforced plastics (FRP) are key materials for lightweight construction in aviation, mobility and energy technology. While they are virtually unbeatable in terms of stiffness and strength, they have one disadvantage: they are only recyclable to a limited extent. The Institute for Plastics Processing (IKV) in Industry and Craft at RWTH Aachen University is therefore researching the new material class of vitrimers as a matrix system that enables the material recycling and reuse of continuous fibre composite structures. The results of this work will be presented in Session 6, Mechanical recycling of CFRP: Vitrimers as enablers, of the 33rd International Colloquium Plastics Technology.
Vitrimers – a new class of materials with recycling potential
Vitrimers form a new class of plastics with properties similar to thermosets. Their key feature is the presence of dynamic covalent bonds that form so-called adaptive networks or covalent adaptive networks (CAN), in the plastic. Under certain defined conditions, the bonds in the network can be specifically broken and re-formed. Vitrimers thus combine the thermal and chemical resistance of classic epoxy resins with the weldability and mendability of thermoplastics (Figure 1). This opens up new options for recycling, repairing and repurposing FRPs. “By using vitrimers, we can not only repair fibre composite structures more easily, but also reuse them in a targeted manner at the end of their life cycle,” explains Prof. Christian Hopmann, Director of the IKV. “This lays the foundation for a truly circular economy in lightweight construction.”
Marc Fette, CEO of the Composite Technology Centre (CTC GmbH), will broaden this perspective on material recycling during the colloquium with a presentation on challenges and potential of FRP recycling for sustainable aviation. Particular attention will be paid to a holistic view of the entire product life cycle with regard to sustainable and economically viable CFRP recycling. Even before components are manufactured, the concept of design-for-recycling or eco-design is essential, enhanced by the selection of suitable materials.
Potential of vitrimer-based composite systems
IKV is investigating the entire value chain of vitrimer-based composite systems in several research projects. First results of this work will be presented in Session 6 at the colloquium. Among other things, this covers the recycling of CFRP components using vitrimer matrix systems. In a demonstration project, epoxy resins with the vitrimer hardener bis-(4-aminophenyl) disulphide (4-AFD) were used to produce carbon fibre sheets that can be functionalised with recycled material after curing. A rib made of vitrimer recyclate applied by hot pressing at 190 °C increases the flexural stiffness and demonstrates the weldability and recyclability of the material.
© IKVAnother project describes a method for the multiple use of continuous fibre-reinforced laminates. Here, IKV demonstrated that continuously fibre-reinforced vitrimer laminates can be separated from each other after their first use and then welded back together again. The structure of the continuous fibres remains intact, enabling a second phase of use without the need for complex chemical separation. The investigations show that the self-healing ability of the material remains intact after several recycling cycles.
Circular strategies for sustainable lightweight construction
The research team at IKV sees the development of vitrimer-based fibre composite systems as a decisive step towards sustainable lightweight construction strategies. The combination of high mechanical performance and material recycling opens up new fields of application – especially for battery housings in electric vehicles or structural aviation components. Session 6 of the colloquium will demonstrate that FRP can be designed in such a way that it is not waste at the end of its life cycle, but raw material for new products. Vitrimers thus enable closing the material cycle for high-performance composites for the first time.
Vitrimer technology and lightweight construction at the 33rd International Colloquium Plastics Technology
The topics of lightweight construction and fibre composites in general will be addressed in
- Session 3: Plastics as a key to scaling the hydrogen economy
- Session 6: Mechanical recycling of CFRP: Vitrimers as enablers
- Session 10: Artificial intelligence in product development and simulation
each with a keynote speech from industry and two scientific presentations from the IKV.
Visitors can gain an insight into the processing and recycling of new materials as part of ‘IKV 360° – Research Live’ at the Technical Centre for Fibre-Reinforced Plastics.