Analysis of Crystallization Kinetics of PLA Filament for Fused Filament Fabrication

This study focuses on characterizing the crystallization kinetics of a PLA 4032D filament, specifically investigating the impact of the extrusion process and different thermal protocols. A principal finding reveals that the PLA filament exhibits a significantly faster crystallization rate compared to the original pellets. This acceleration is attributed to the thermomechanical stresses and potential partial degradation that the polymer experiences during filament extrusion. Two distinct calorimetric protocols, “melt” (erasing prior history) and “solid” (preserving nucleation seeds), were employed. The “solid” protocol demonstrated notably faster kinetics, approximately half the time of the “melt” protocol, underscoring the crucial role of pre-existing nuclei—a condition relevant to the short residence time in Fused Filament Fabrication (FFF) liquefiers. The research also confirmed the phase transition between α′ and α crystalline forms in PLA 4032D, which is highly dependent on crystallization temperature. A kinetic model was successfully developed to accurately predict the evolution of crystallinity for both phases, effective for crystallization from the melt and in the presence of nuclei. These results are crucial for optimizing PLA filament production and controlling the final properties of 3D-printed parts, contributing to a deeper understanding of PLA behavior under processing conditions and improving FFF efficiency.