Optimizing TPU performance: The role of mold temperature on injection molding of TPU

Frederik Grønborg*, David Bue Pedersen, Jon Spangenberg, Anders Egede Daugaard, Markus Lothar Susoff

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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This study explores the influence of mold temperatures below 60°C on thermoplastic polyurethane (TPU) properties during injection molding, focusing on phase separation and its impact on mechanical, thermal, and viscoelastic properties. Using a combination of micro-indentation, temperature scanning stress relaxation, and conventional characterization methods, the research highlights how increased mold temperatures promote more distinct phase separation, enhancing mechanical stability and physical properties. The novel use of micro-indentation revealed a gradient in material stiffness from the surface to the core of injection-molded samples, attributed to differential cooling rates and shear forces, which affect phase separation and crystallinity of the hard domains. These insights are critical for applications requiring specific surface properties and underscore the importance of understanding the interplay between chemical composition and processing conditions for optimizing TPU properties. Furthermore, the paper shows that tensile testing, differential scanning calorimetry, and Shore hardness cannot quantify the effects of mold temperatures below 60°C. The research highlights the influence and importance of chemical composition, rheological history, and thermal history on the properties of TPU.
Original languageEnglish
JournalJournal of Applied Polymer Science
Publication statusAccepted/In press - 2024


  • Differential scanning calorimetry (DSC)
  • Mechanical properties
  • Molding
  • Morphology
  • Structure-property relationships


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