The Understanding the Processing Window of Virgin and Recycled Bio-based Filaments for 3D Printing Applications

Commercial available filaments made from poly(lactic) acid (PLA) are selected for potential use in 3D printed parts by fused deposition modeling. Virgin materials (PLA Eum, Z-PLA Pro), but also recycled matrices (PLA 2Life, PLA Eubio), and one filled with wood fibers (PLA Woodfir) have been considered. Then, a lab-made filament (PLA Nature) is realized by extruding PLA pellets. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and rheological measurements are used to determine initial degradation temperature, glass transition, melting temperature, and complex viscosity as a function of time and material pre-drying. A preliminary investigation of thermal properties enables the materials' processing window to be validated in order to prevent the deterioration during the process. PLA Nature and PLA Woodfir melt around 170 degrees C, whereas all of the other biopolymers show a lower melting point (around 150 degrees C). The temperature at which thermal degradation began is always greater than 260 degrees C. However, good stability of rheological parameters over time at 210 degrees C is not confirmed for all bio-filaments. In particular, for Z-PLA Pro and PLA Eubio, a significant reduction of complex viscosity is verified after a few seconds of testing. Drying samples have been shown to improve the long-term stability of complex viscosity.