Thermally Induced Phase Separation of Recycled Polyethylene Terephthalate: Crystallization Behavior, Thermal Properties and Processability for Laser Sintering

ABSTRACT Thermally induced phase separation (TIPS) offers a promising route for tailoring the crystallization behavior and thermal properties of recycled polyethylene terephthalate (rPET) for powder‐based additive manufacturing. In this study, rPET powder with near‐spherical morphology and a narrow particle size distribution was successfully prepared via the solid–liquid (S–L) phase separation mechanism. The TIPS process induced a significant structural transition from an amorphous to a semi‐crystalline state, as confirmed by X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses. The effects of polymer concentration (5–15 wt%) and processing temperature (180°C–200°C) on particle morphology, size distribution, and crystallization behavior were systematically investigated. Comprehensive characterization including scanning electron microscopy (SEM), DSC, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and XRD revealed that the TIPS‐derived powder exhibited enhanced crystallinity, a broadened sintering window, and preserved chemical integrity. The optimal powder, prepared at 10 wt% concentration and 190°C, displayed an average particle size of approximately 52 μm with favorable flowability. Preliminary laser powder‐bed fusion (L‐PBF) trials demonstrated the successful fabrication of dense monolayer films, validating the processability of TIPS‐prepared rPET powder for additive manufacturing. This work establishes a sustainable and effective approach for converting recycled semi‐crystalline polymers into high‐quality L‐PBF feedstock.