Rheology-Informed Working Thresholds for HME/FDM Processability in a PVA-Sorbitol-Paracetamol Model System

Area of Science:

• Pharmaceutical Technology
• Materials Science
• Rheology

Background:

• Oscillatory rheology is crucial for hot-melt extrusion (HME) and fused deposition modeling (FDM).
• Translating rheological data into practical formulation screening criteria for HME/FDM remains challenging.
• This study re-analyzes a PVA-sorbitol-paracetamol dataset to establish processability thresholds.

Purpose of the Study:

• To derive rheology-informed working thresholds for HME/FDM processability.
• To develop a compact, formulation-specific screening framework for PVA-based systems.
• To interpret rheological descriptors against empirical extrusion and printing data.

Main Methods:

• Utilized temperature-ramp oscillatory rheology to extract formulation descriptors.
• Measured complex viscosity (|η*|) at 185 °C and 200 °C.
• Calculated Processing Window Fraction (PWF) and analyzed crossover temperatures.

Main Results:

• Identified specific viscosity thresholds for successful HME/FDM: ~0.460 kPa·s at 200 °C and ~0.899 kPa·s at 185 °C.
• PVA-sorbitol formulations (S1.25, S1.5) showed good extrusion compatibility; S1.75 indicated over-plasticization.
• Paracetamol addition (P5-P15) reduced viscosity while maintaining processability; PWF indicated formulation temperature flexibility.

Conclusions:

• Process-temperature complex viscosity and PWF provide a robust screening framework for PVA-based HME/FDM.
• The derived thresholds offer operational guidance for formulation development.
• Prospective external validation is recommended for the proposed rheological thresholds.