Circular economy-driven additive manufacturing: A model for recycling PLA/copper composites through multi-extrusion processing

Abstract

ISO 52,900 material extrusion (MEX) 3D printing utilises materials to manufacture customisable components. End of life parts lead to accumulation of nondegradable plastic wastes with detrimental environmental impacts. Circular methods to close the loop will reduce the wastes that would end up in landfill. Recycling polylactic acid (PLA) has been reported to negatively impact the mechanical properties compared to the virgin material. We investigate the addition of copper microparticles, found in old electronic parts, to recycled PLA and its effects on the mechanical properties. We pelletise the extruded filament and use it as the feedstock for another further extrusion to simulate the recycling process. The first extrusion showed a good copper dispersion in the PLA matrix, the novelty of the second pass was to create a model to evaluate mechanical performance. Commercially available 60wt% copper filament was used as a benchmark. Tensile strength and modulus of extruded filament were found to be 48.8 MPa and 2.3 GPa for sample with quarter copper loading, respectively. All extruded filaments outperformed commercial filament in fracture toughness, with values of 1.06 MPa√m for quarter copper loading and 1.1 Mpa√m for half copper loading, with re-extrusion reducing fracture toughness by 34% and 9%, respectively.