CircularEpoxy
CircularEpoxy is devoted to the economical production of recyclable epoxy-based thermosets and their fiber-reinforced composite materials. The materials developed in CircularEpoxy pave the way for composite components with an extended service life (due to the possibility of repair and maintenance). In addition, recyclability and easier disassembly enable the realization of closed-loop recycling processes for composite structures.
Project Partners
- Isovolta AG, Coordinator
- Polymer Competence Center Leoben GmbH
Motivation and Goals
The composite industry is faced with the task of meeting the challenges of the European Green Deal, which aims to achieve climate neutrality by 2050. However, establishing a circular economy for composite structures is challenging as the components are usually made up of a wide variety of materials (e.g., polymers, fillers and metals). The repair, maintenance and recycling of composite materials is particularly difficult, as the matrix polymers used (e.g., epoxy-based thermosets) cannot be dissolved, melted or reshaped due to their covalent network structure. Interior components are therefore often not adequately sorted for cost reasons and around 15% of the aircraft components that are currently sent to landfill come from cabin components.
Thus, CircularEpoxy aims at the economical production of recyclable fiber-reinforced composite materials, which are characterized by (a) a unique possibility for maintenance and recycling of interior components, (b) an increased service life (reparability),
(c) more efficient production methods (thermal reshaping of semi-finished products), (d) energy-saving distribution, (e) adjustable fittings (for on-site assembly), (f) the absence of chemicals that are harmful to health and the environment (including anhydrides) and (g) high mechanical strength and fire resistance. As a new generation of fiber-reinforced composite materials, these materials combine the properties of classic thermosets (which cannot be repaired, reshaped or recycled due to their covalent network structure) with the processing properties of thermoplastics. The material development in CircularEpoxy is based on commercially available epoxy resins, which are equipped with dynamically exchangeable chemical groups. By thermally activating these groups, a viscoelastic flow of the material is achieved without changing the average cross-linking density. The targeted control of the physical properties is subsequently used for the assembly, production, repair or recycling of the materials (e.g., separation of fillers and polymer matrix).
Main Goals
Development and production of epoxy-based fiber-reinforced composite materials that are characterized by the following properties:
- Improved repairability (including patch-free repair of scratches and delaminations)
- Increased recyclability (recovery of fibers and the chemically cross-linked resin matrix)
- Thermal malleability (production of cured semi-finished products that can be reshaped in short process times)
- Weldability (establishment of new joining and assembly processes)
- High creep resistance, rigidity and fire resistance
Objectives and Approach
CircularEpoxy is intended to initiate a change in the production of epoxy-based composite materials, as it enables the production of cured thermoset prepregs that can be repaired and recycled due to the dynamic network points. Despite being fully cured, these new recyclable prepregs can be processed in the same way as organic sheets (malleability) and welded, paving the way for an efficient and flexible production of aerospace components by end users. In addition, simpler quality control is made possible (control of intermediate steps vs. control of the finished component) and defective prepreg can be replaced more easily, which reduces the overall costs of the process chain.
Due to the dynamic covalent network sites introduced, the materials can not only be repaired but also chemically recycled (without the use of solvents that are hazardous to health and the environment). The networks are degraded by transesterification in the presence of water vapor or primary alcohols, allowing the polymer matrix to be separated from the fibers. The degradation reactions preferentially form carboxylic acids and alcohols, which can be used as new crosslinkers in thermally cured epoxy resins.
„Dynamic polymer networks are key materials for future recyclable products. CircularEpoxy is advancing the industrial application of this new class of materials for numerous fields.“
Downloads & Links
Funding Body
The project (project number: 58728995) is funded by the Federal Ministry for Innovation, Mobility and Infrastructure (BMIMI) as part of the “Kreislaufwirtschaft und Produktionstechnologien 2024” call. The program is managed by the FFG.
