Assessment of Recycled PLA-Based Filament for 3D Printing

This study investigated the possibility of replacing virgin matrices with recycled polymers in additive manufacturing (AM). In this regard, two commercial filaments, made from polylactide acid (PLA)—the second (here referred to as recycled) obtained from the recovery of waste production of the first one (here referred to as virgin)—were initially characterized using infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and dynamic rheology. Then, filaments were extruded in a 3D printer and characterized by dynamic mechanical analysis (DMA). Despite a small reduction in the intensity of correspondence of typical absorption bands of the PLA polymer, in the case of the recycled material compared to the virgin one (as attested by IR spectra), the thermal-mechanical results allow us to attest the very similar characteristics of recycled and neat filaments. The onset of thermal degradation was found at around 315 °C in both systems. Both materials exhibited the same frequency- and time-dependent trends of the complex viscosity, with a reduction of approximately 30% after 10 min of testing. When samples were dried at 80 °C under vacuum for 10 h, the stabilization of rheological features against time was improved. There was no significant difference in the storage modulus (E’) and dissipation factor (tan delta) of 3D printed parts made with different types of PLA-based filaments.