The present work is concerned with the investigation of the slit die extrusion of molten polymers, and a systematic strategy is developed for the modelling of its major aspects. The objective is to provide a fundamental understanding of the flow phenomena within such a die, coupled with thermal and mechanical interaction of melt and die body, and to provide user friendly software for analysis and design. Isothermal, non-Newtonian flow in the large aspect ratio channels of such dies is modelled using a Hele-Shaw formulation. The pressure field in the die causes a change of the flow channel dimensions, and hence alters the melt distribution. An experimental technique is applied to determine this die body deflection in a 1.3m commercial die; it is found to be substantial. Modelling of the die deformation using a commercial 3-D finite element package is described, with the load being based on a pressure field previously determined in the undeflected flow channel geometry. Prompted by unsatisfactory results, an algorithm is developed to evaluate the die body deflection iteratively, by coupling a 2-D thick plate analysis with the Hele-Shaw flow analysis, resulting in significantly improved results. Modelling of the conjugate melt flow/die heat transfer problem on the die cross-section is also carried out. Viscous heat generation, conduction and convection energy transport in the melt coupled with heat conduction in the die body are considered, together with the influence of electrical die heating and heat losses from the die surfaces by convection and radiation. Conclusions are drawn on thermal aspects of die design and operation. A graphical user interface embedded in Microsoft Windows is developed for a number of finite element codes, facilitating their use by non-specialists, and providing graphical displays of results. An outline of the operation of the complete package is described, including a convenient contouring algorithm.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:638761 |
| Date | January 1993 |
| Creators | Sander, R. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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