A dimensionless rheology-based extrusion map as a predictive tool for hot-melt extrusion processability

Predicting the processability of polymeric materials in hot-melt extrusion remains a critical challenge in continuous manufacturing due to the complex transition from powder feeding to melt flow under dynamic processing conditions. In this work, we present a unified and predictive methodology for construction an extrusion processability map based on dimensionless rheological criteria. The framework first assesses powder feeding behavior using solid-state indicators, including the flowability index ( f f c ), friction ratio ( F R ), and Froude number ( F r d ), to characterize feed consistency and uniformity. The analysis is subsequently extended to the melt-processing stage in a twin-screw extruder, where extrudability is described using dimensionless numbers that capture viscous, elastic, and inertial effects, namely the Bingham ( B n ), Deborah ( D e ), Weissenberg ( W i ), and Reynolds ( R e ) numbers, along with the die swell ( B ) parameter. These criteria are integrated into a first-order predictive model that enables identification of stable extrusion processing windows. The resulting processability map provides mechanistic insight into the behavior of polymeric systems under defined operating conditions, reducing reliance on empirical trial-and-error approaches. Early identification of processing limitations supports efficient process optimization, leading to reduced material waste, lower energy consumption, and a smaller environmental footprint. While demonstrated using pharmaceutical polymer systems, the proposed methodology is broadly applicable to extrusion-based manufacturing across materials and chemical engineering.