The project investigated the feasibility of a circular economy for polymer‑bound permanent magnets, a material class that is increasingly used in sensors, actuators and electric‑vehicle drives. The main scientific objective was to develop and evaluate recovery routes for the hard‑magnetic fillers (NdFeB and SrFeO) that are embedded in either duroplastic or thermoplastic polymer matrices. The study combined a comprehensive material‑flow analysis with experimental recycling trials and a detailed characterization of the recovered powders and the re‑fabricated magnets.

First, a process‑chain analysis quantified the economic and environmental burdens of the current supply chain, including transport distances for rare‑earth elements. The analysis highlighted that the main bottleneck for a circular economy is the oxidation of the magnetic particles during conventional pyrolysis. To mitigate this, the consortium tested a pyrolysis step under inert nitrogen atmosphere. The inert‑gas process suppressed the formation of an oxide layer, but still caused a 20 % loss of magnetic performance, yielding a remanent flux density of 720 mT in the recovered NdFeB powder—an improvement over the 600 mT obtained with air‑atmosphere pyrolysis, yet still below the 1 T benchmark of virgin material.

Because the inert‑gas pyrolysis is energy intensive, a second strategy was pursued for duroplastic magnets. The demagnetized rings were milled into fine (1.5 mm) and coarse (3.5 mm) granulates, which were then mixed with epoxy resin and a magnetic compound (either isotropic NdFeB or anisotropic SrFeO). The granulates were processed by pressing and injection moulding into new magnet blocks. Magnetic measurements showed that the remanence of the pressed samples could be maintained within 20 % of the virgin material, and the magnetic flux density reached up to 950 mT for the NdFeB‑based composites. The anisotropic SrFeO composites exhibited a coercivity of 1.2 kOe and a remanence of 0.45 T, close to the performance of the original thermoplastic magnets.

For thermoplastic magnets, a material‑based recycling route was developed. After thermal ageing at 120–160 °C, the polymer was ground and re‑mixed with fresh epoxy and magnetic filler. The resulting re‑fabricated magnets, produced by injection moulding, displayed a remanence of 0.8 T and a coercivity of 1.0 kOe, representing a 15 % reduction compared to new parts but still suitable for many sensor applications. Differential scanning calorimetry and thermogravimetric analysis confirmed that the recycled polymer retained sufficient melt flow properties for processing.

The project also produced a quantitative assessment of the economic and ecological benefits of the proposed recycling routes. The analysis indicated that the energy consumption of the inert‑gas pyrolysis exceeds that of the mechanical recycling by roughly 30 %, while the latter offers a higher overall material recovery rate (≈ 70 % of the magnetic filler). The life‑cycle assessment showed a reduction of CO₂ emissions by up to 40 % when using the mechanical recycling route compared to a virgin‑material baseline.

Collaboration among the partners was structured around complementary expertise. The Institute of Materials Science and Technology (LKT) in Erlangen led the experimental work on pyrolysis and mechanical recycling. Magnetworld AG in Jena supplied industrial‑scale magnet samples and provided data on production volumes and transport logistics. FIT‑Umwelttechnik GmbH in Wolfsburg contributed life‑cycle assessment tools and economic modelling. Prof. Dr.-lng. Dietmar Drummer coordinated the project and facilitated the integration of the results into a design for a future circular economy of polymer‑bound permanent magnets. The project was carried out over a multi‑year period, with all milestones met according to the agreed schedule, and was funded through a German research grant that supported the development of sustainable materials technologies.