Optimierte Entformung mikrostrukturierter Spritzgussbauteile durch Werkzeugbeschichtungen

Translated title of the contribution: Optimized demolding of microstructured injection molding parts through tool coatings

Lukas Windischbauer

Research output: ThesisMaster's Thesis


The aim of this work was to improve the demoldabilty of microstructured injection molded polymer parts by the coating of mold inserts. In a first step unstructured mold inserts were coated with titanium nitride (TiN), tungsten disulfide (WS2), chromium nitride (CrN) and polytetrafluorthylene (PTFE). The coated mold inserts were tested with cyclo olefin copolymer (COC), polymethylmethacrylate (PMMA) and polycarbonate (PC) under variotherm conditions. The ability of parts being demolded and the tendency of polymer particles sticking to the insert were observed. On the one hand the PTFE coating appeared to be the best solution for COC and PMMA. PC could be demolded without material sticking with and without coating. So no improvement could be observed. On the other hand this coating can cause problems because of its low durability. This can influence the effectivity of the coating in terms of demoldability improvement. Furthermore PTFE particles being stuck to the polymer part can cause problems in optical or fluidic applications. The TiN coating improved the demolding behavior only with PMMA. The coating is much more durable than PTFE. The results of the WS2 coating were good, especially with COC, but the coating was not investigated further because of different reasons. The rough coating surface can influence optical and fluidic applications. Furthermore, the deposition method cannot guarantee a constant quality. Additionally, the coating appeared to degrade both in practical tests and in literature. The CrN coating showed bad demolding properties with all tested polymers. The coating was not used for any further tests. Because of the great durability of the TiN coating, this material was used for tests with microstructured mold inserts. The tests revealed that the demoldability with TiN-coated mold inserts was worse than with uncoated inserts with all tested polymers. These results are caused by three effects. The TiN coating builds untercuts at the top edges of the microstructures. This effect is especially effective in combination with sharp edges. Another reason are cracks at the bottom of the microstructures which occur because of stresses inside the coating in combination with high demolding forces and low stiffness of the thin mold inserts (thickness 300 µm). In case these cracks are filled with polymer melt, the demolding force is increased. Additionally, the coating thickness decreases with decreasing draft angle. At draft angles lower than 7°, where the highest friction occurs, there is no visible coating. Because of these results for the TiN coating, other microstructured mold inserts were coated with PTFE. The first tests were performed with cyclo olefin polymer (COP). The demoldability was significantly better than without the coating. A long run test with cyclo olefin copolymer (COC), which was performed with a different mold, proved the effectiveness of the coating for the improvement of the demoldability for at least 1000 parts.
Translated title of the contributionOptimized demolding of microstructured injection molding parts through tool coatings
Original languageGerman
  • Lucyshyn, Thomas, Co-Supervisor (internal)
  • Holzer, Clemens, Supervisor (internal)
Award date1 Jul 2016
Publication statusPublished - 2016

Bibliographical note

embargoed until 27-05-2021


  • Optimized
  • demolding
  • of
  • microstructured
  • injection
  • molding
  • parts
  • through
  • tool
  • coatings

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