INVESTIGATION ON THE FEASIBILITY OF PRODUCING POLYMER-BASED MAGNETIC COMPOSITES FROM RECYCLED PERMANENT MAGNETS USING FUSED DEPOSITION MODELLING

Polymer-based composites with magnetic properties represent a promising class of materials that combine conventional polymer characteristics (low density, high electrical resistance, enhanced flexibility, and processability, among others) with magnetic properties typically associated with ferromagnetic or ferrimagnetic metals and alloys. In the present study, micrometric particles of a neodymium-iron-boron (NdFeB) alloy are compounded with a flexible thermoplastic matrix comprising polybutylene adipate-co-terephthalate (PBAT). The NdFeB alloy is recovered from permanent magnets of obsolete hard drives and is demagnetised, ground to powder under an inert atmosphere, and finally sieved to a particle size below 50 μm. The obtained powder is mixed with the polymer using a twinscrew extruder. The composite material containing the NdFeB particles is then processed to obtain a calibrated filament, which is used for the fused deposition modelling (FDM) three-dimensional (3D) printing of magnetic composites. Different routes to improve the ferromagnetic behaviour are investigated, including increasing the filler content up to 50 wt%, orientating the particles during the 3D process by printing directly onto a permanent magnet and subsequent magnetisation of the samples using a pulse magnetiser. The results of the structural, thermomechanical, and magnetic characterisations are presented and discussed.