Related Experiment Video
Updated: Feb 3, 2026

Design of an Open-Source, Low-Cost Bioink and Food Melt Extrusion 3D Printer
Published on: March 2, 2020
The application of temperature-composition phase diagrams for hot melt extrusion processing of amorphous solid
Dana E Moseson1, Lynne S Taylor1
1Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University, West Lafayette, IN 47907, United States.
Abstract:
Hot melt extrusion (HME) can be used to produce amorphous solid dispersions (ASDs) at temperatures below the drug's melting point if the drug and polymer exhibit melting point depression. However, the risk of residual crystallinity becomes significant. The purpose of this study was to apply the temperature-composition phase diagram to the HME process, correlating process conditions to ASD residual crystallinity, and identifying the formulation critical temperature, which defines the theoretical minimum processing temperature. The phase diagram of indomethacin (IDM) and polyvinylpyrrolidone/vinyl acetate copolymer (PVPVA) was generated using melting point depression measurements coupled with Flory-Huggins theory. Extrudates were manufactured above, at, and below the formulation critical temperature (Tc) as identified from the phase diagram, with a range of residence times, and characterized for crystallinity. Below the Tc, a fully amorphous sample could not be prepared. Above Tc, sufficient residence time led to amorphous samples. A processing operating design space diagram with three regimes was generated to correlate temperature and residence time factors with process outcome. In conclusion, phase diagrams provide a rational basis for designing hot melt extrusion processes of amorphous solid dispersions to minimize residual crystalline content, delineating the minimum processing temperature based on thermodynamic considerations.
Related Concept Videos
Phase Diagrams
Phase Transitions: Melting and Freezing
Structures of Solids
Phase Diagram
Molecular and Ionic Solids
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Network Covalent Solids
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...

