This study investigates the feasibility of mechanically recycling post-industrial polypropylene (PP) waste into homogeneous pellets and 3D-printable filaments for fused deposition modeling (FDM) without the use of chemical additives. The primary objective is to evaluate whether recycled polypropylene can retain sufficient mechanical, thermal, and structural integrity for additive manufacturing applications. The recycled PP was processed using single-screw extrusion to produce pellets and filaments, followed by fabrication of test specimens through injection molding and FDM printing. Mechanical performance was evaluated through tensile testing in accordance with ASTM D638, while thermal behavior and structural integrity were assessed using melting point analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results demonstrate that pellet-based recycled polypropylene retained approximately 90% of the tensile strength of virgin polypropylene, whereas filament-based recycled polypropylene retained approximately 80%. FTIR analysis confirmed preservation of the polypropylene chemical backbone with no significant evidence of oxidative degradation, while SEM observations revealed minor micro voids and interlayer features associated with FDM processing. The successful fabrication of dimensionally stable 3D-printed components further confirms the processability of recycled polypropylene under standard FDM conditions. These findings indicate that mechanically recycled polypropylene can be effectively utilized in additive manufacturing, offering a simplified and sustainable pathway for polymer reuse without chemical modification.
