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 contribution | Determination of the transition temperature at different cooling rates and its influence on prediction of shrinkage and warpage in injection moulding simulation |
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Original language | German |
Qualification | Dipl.-Ing. |
Supervisors/Advisors |
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Award date | 17 Dec 2010 |
Publication status | Published - 2010 |
Bibliographical note
embargoed until nullKeywords
- Transition-Temperature
- Ttrans
- specific heat capacity
- cp
- cooling rate
- shrinkage
- warpage
- injection moulding simulation