Transport processes in polymer extrusion and optical fiber drawing

The numerical modeling of the transport processes in materials processing, particularly for polymers and glass, is discussed. Two important manufacturing processes concerned with these materials, the optical glass fiber drawing and the plastics screw extrusion processes, are considered in detail. Heat transfer and fluid flow considerations play a very important role in determining the properties of the final product. The governing equations, the relevant boundary conditions, and the numerical study of these processes are discussed. The importance of material characterization in an accurate numerical modeling is brought out, along with the coupling between the process and the resulting properties. The various concerns and computational difficulties that arise due to the non-Newtonian behavior of plastics, exponential temperature dependence of glass viscosity, complex geometry, free surface flow, conjugate transport, material movement, and variations in the velocity level due to the large changes in cross- sectional area are considered. Additional mechanisms such as surface tension effects and chemical reactions are also important. Some of the important methods to treat these problems and challenges are presented. A few characteristic numerical results are discussed and validated by comparisons with experimental results. The implications of such results in improving practical systems is also considered.