| Micocellular plastics,characterized by cell size smaller than 10μm and cell density larger than 109cells/cm3,are drawing increased attention due to their unique properties and potential applications.In this study,based on theories of polymer theology,hydrokinetics and thermodynamics etc.,the governing equations of a continuous screw process in the capillary nozzle are presented.The equations are solved by using finite element software POLYFLOW and postprocess software FIELDVIEW.Supercritical carbon dioxide(CO2),a potential replacement of the traditional screw agents(chlorofluorocarbons),is applied to produce microcellular screw of polystyrene.The design of screw with a desired cell structure mainly depends on the selection of proper operating conditions.The contraction flow in the screw is simulated with POLYFLOW to predict profiles of pressure,velocity,shear—rate and stress.The results show that:1.In the molding equipment,a supercritical fluid in jection system was designed.The system can be used to control the injected Pressure temperature and flux of the supercritical CO2,Some improvement for the extruder barrel screw configuration,and gas injection inlet has been done.During the research some novelty screw element were specially designed for the foaming process.A gear pump system was constructed and mounted directly at downstream of screw extruder.2.In the molding of the foaming Process,the effects of the material composition,temperature,Pressure and gas concentration on the microscopic strueture of the sample were preliminary studied.Based on study,an optimized extrusion processing route for PS/CO2 microcellular foam were established.By reconstructing the conventional extrusion equipment and optimizing process control,the microcellular PS/CO2 foam was successfully extruded in this study. Integrated with the result of simulation,screw for forming was designed,and Micocellular screw extrusion molding device was constructed preliminary.
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