Ermittlung der Transition-Temperature bei verschiedenen Kühlraten und deren Einfluss auf die Vorhersage von Schwindung und Verzug in der Spritzgusssimulation

Translated title of the contribution: Determination of the transition temperature at different cooling rates and its influence on prediction of shrinkage and warpage in injection moulding simulation

Gilbert Knapp

Research output: ThesisMaster's Thesis

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Abstract

In injection moulding simulation the phase change from melt to solid state is usually simplified by using a so called transition-temperature (Ttrans), also known as noflow-temperature. Above this temperature the polymer is assumed to behave like a fluid and below this temperature it is regarded as a frozen solid without any flow velocity. A common method to determine this material parameter is the differential scanning calorimetry (DSC) with a cooling rate of typically 20 K/min. This cooling rate is much lower compared to the injection moulding process. It can be expected that the way of determining the transition-temperature has an influence on the prediction of shrinkage and warpage with commercial injection moulding simulation tools. In this work the transition-temperature and the specific heat capacity cp of four amorphous and four semi-crystalline polymers was determined using DSC-runs at different cooling rates up to 100 K/min. The dependence of the transition-temperature was described as a function of cooling rate. There was a weak influence of the cooling rate on the transition-temperatures of the investigated amorphous polymers, but the transition-temperatures and in consequence the peak of the cp-curves of the semi-crystalline polymers were significantly shifted to lower temperatures with increasing cooling rate. The obtained transition-temperatures and cp-data of the selected semi-crystalline polymers were then used in injection moulding simulations with the commercial software package Autodesk-Moldflow-Insight to calculate the shrinkage and warpage of boxshaped test parts. The test parts were injection moulded and the dimensions of these boxes were determined using an optical 3D-scanner. Finally, the simulation results were compared with the experimental values of the injection moulded boxes. The results showed a strong influence of the transition-temperatures and cp-data on simulation results of the 3D-model and a very low influence for the 2,5D-model. Generally, the simulation results of the 3D models matched better with experimental values. Transition-temperatures and cp-data measured at higher cooling rates even improved the 3D simulation results for several dimensions.
Translated title of the contributionDetermination of the transition temperature at different cooling rates and its influence on prediction of shrinkage and warpage in injection moulding simulation
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Holzer, Clemens, Supervisor (internal)
  • Lucyshyn, Thomas, Co-Supervisor (internal)
Award date17 Dec 2010
Publication statusPublished - 2010

Bibliographical note

embargoed until null

Keywords

  • Transition-Temperature
  • Ttrans
  • specific heat capacity
  • cp
  • cooling rate
  • shrinkage
  • warpage
  • injection moulding simulation

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