Impact of Drug Loading and Mannitol on Mechanical Properties and Printability of Filaments: A Comparative Study of Single-Screw Extruder vs. Twin-Screw Extruder

The manufacturing of drug-loaded filaments aimed for fused deposition modeling (FDM) three-dimensional printing (3DP) is still an important challenge because the filament mechanical profile and printing performance depend on both formulation and process-related factors. This study investigated the impact of extrusion technology on the mechanical properties and printability of paracetamol-loaded polyvinyl alcohol filaments with variable compositions. Filaments with compositions according to a full-factorial design were processed by single-screw extrusion (SSE) and twin-screw extrusion (TSE). Mechanical properties were assessed using the 3-point bending test and stiffness test. The thermal behavior of the components was evaluated through differential scanning calorimetry (DSC), while printability was evaluated through feeding and printing tests. Both formulation factors affected mechanical performance. High paracetamol content generally reduces stiffness and flexural resistance while increasing deformation capacity, suggesting a secondary plasticizing effect in the studied concentration range. Mannitol exhibited limited plasticizing efficiency, with flexibility decreasing at high ratios. DSC indicated partial crystallinity after extrusion, with TSE showing lower residual melting enthalpies than SSE. TSE filaments provided higher model reproducibility, broader mechanical ranges, and higher printability scores. This study shows that formulation effects depended strongly on extrusion technology and highlights TSE as a more robust platform for producing printable pharmaceutical filaments.