Eco-sustainable magnetic polymer composites using recycled and rare-earth-free hard magnetic fillers

Abstract

Biodegradable polymer matrices, poly(ε-caprolactone) (PCL), and poly(butylene succinate-ran-butylene adipate) (PBSA) were used to fabricate magnetic composites with recycled NdFeB and rare earth-free lab-synthesized ferrite fillers (SrFe₁₂O₁₉ and SrFe₁₂O₁₉–CoFe₂O₄) across a wide filling range (1–90%). Results obtained by differential scanning calorimetry, polarized light optical microscopy, and phase contrast microscopy, indicated that the magnetic particles tend to aggregate, leading to bimodality in the crystallization process, which can be attributed to distinct regions of the composites with well-dispersed and aggregated particles. Notably, ferrite fillers exhibited lower magnetic anisotropy compared to NdFeB, enabling magnetic saturation at lower fields. These results demonstrate the potential of combining biodegradable polymers with sustainable magnetic fillers for eco-friendly circular economy applications.