Plastic waste recycling in additive manufacturing: Recovery of polypropylene from WEEE for the production of 3D printing filaments

The inefficient management of wastes recovered from electric and electronic apparatuses (the so-called WEEE or e-waste) has become a severe global concern in the last years, since the indiscriminate accumulation of wastes containing hazardous material poses serious risks for the environmental, as well as for the human health. Despite the continuous development of innovative and efficient technologies for the mechanical recycling of WEEE plastics, the effective re-utilization of these fractions is often limited by their poor value-added. In this work, we propose a strategy for the valorization of a typical WEEE plastic stream recovered from small appliances (mainly composed on polypropylene filled with talc particles) through the formulation of filaments suitable for Fused Filament Fabrication (FFF) 3D printing processes. Preliminary spectroscopic analyses on the WEEE plastics allowed separating the sample in two streams, according to the different content of talc. Both streams were first characterized from a rheological point of view, aiming at assessing their 3D printability. Then, the mechanical properties and the morphology of the filaments (obtained after a close optimization of the extrusion conditions) were evaluated; the obtained results indicated the achievement of a regular geometry and mechanical properties comparable to those of commercial filaments. Finally, 3D printed specimens showed a satisfactory quality in terms of resolution and definition, demonstrating the possibility of profitably enhancing the value-added of WEEE plastics, using them as feedstock to produce sustainable 3D printing filaments.