Date of Award
Doctor of Philosophy (PhD)
Dr. J. Vlachopoulos
A fully-predictive steady-state computer model has been developed for a single screw plasticating extruder. Included in the model are:
(i) a model for the flow of polymer solids in the feed hopper,
(ii) a variation of the Darnell and Mol model for solids flow in the extruder screw channel,
(iii) a modification of the Tadmor melting model for the melting zone in the screw channel,
(iv) an implicit finite difference solution of the conservation of mass, momentum and energy equations for the flow of the polymer melt in the screw channel and die, and
(v) a predictive correlation for the extrudate swell at the die exit.
A temperature and shear rate dependent viscosity relation is used to describe the melt flow behaviour in the model. The parameters in the viscosity relation are obtained by applying regression analysis to Instron capillary rheometer data. Extrudate swell theories developed for capillary rheometers have been utilized in the development of the correlation are the prediction of the extrudate swell at the extruder die exit. The parameters in the correlation are obtained by applying regression analysis to Instron extrudate swell data.
Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions (i.e. screw speed, barrel temperature profile, etc.), the following are predicted:
(i) mass flow rate of the polymer,
(ii) pressure and temperature profiles along the extruder screw channel and in the die, and
(iii) extrudate swell at the die exit.
The overall extruder model predictions have been confirmed with experimental results from a 1 1/2 inch (38 mm) diameter, 24:1 L/D single screw extruder with a 3/16 inch (4.76 mm) diameter cylindrical rod die. High- and low-density polyethylene resins were used.
Agur, Enno Eric, "Numerical Simulation of a Single Screw Plasticating Extruder" (1982). Open Access Dissertations and Theses. Paper 1601.