The Use of Biodegradable Poly(ε-Caprolactone) as a Matrix for Preparing Micro-Composites with NdFeB Recycled Magnetic Particles

Abstract

Neodymium-iron-boron (NdFeB) magnets are essential because they show optimized magnetic properties for clean energy applications. They suffer nevertheless from their rare earth mine security of supply. The European Union considers them as key materials, encouraging their recycling to reduce the supply dependence on other countries. In this work, biodegradable poly(ε-caprolactone) (PCL) is used to obtain PCL/NdFeB micro-composites, with recycled NdFeB loadings of 0.25, 0.50, 0.75, 1.00, and 5.00 wt.%. Three different preparation techniques are employed: “melt mixing,” “solution-mixing,” and “solution mixing and precipitation.” The crystallization behavior is studied by Differential Scanning Calorimetry (DSC) and morphology by Polarized Light Optical Microscopy (PLOM) and Phase Contrast Microscopy (PCM). Non-isothermal and isothermal DSC experiments showed that the nucleation effect of NdFeB magnetic micro-particles on PCL is more effective in the case of micro-composites prepared by “solution and precipitation”. Non-isothermal experiments evidenced the largest increase in the crystallization temperature, while the isothermal experiments showed the highest acceleration in the overall crystallization rate for the samples prepared by “solution and precipitation”. Besides, self-nucleation tests confirmed these samples' most significant increase in nucleation efficiency. Finally, the nucleation effect of NdFeB micro-particles on PCL is also proven by the reduction in spherulitic size observed after NdFeB particle incorporation.