Polymer Engineering Center > Research > Wire Coating and Pipe Extrusion

The center attacks problems with viscoelasticity during the extrusion of pipes and wire coating. During high-speed wire coating, melt emerges from an annular die and is drawn onto the metal wire by a vacuum, applied inside the annular extrudate, or melt cone. In continuous plastic pipe extrusion, melt from an annular die is freely drawn into a sizing sleeve. Positive air pressure is typically applied inside the pipe to ensure good contact with the sizing sleeve. In both cases, the final product is typically much thinner than the extruded melt. Being able to predict characteristics of finished product will help during process as well as to understand the underlying physics of these techniques. Although these processing techniques are used extensively in industry, there have been no general predictive models. Within this research project, these flow fields are investigated using both analytical and numerical methods. For the case without applied pressure differences, analytic solutions can be derived. When additional pressures are applied, such as the vacuum in wire coating, numerical solutions can be constructed and examined. Design curves are then constructed from the solutions to these models. These curves are helpful in predicting operating conditions for pipe extrusion and wire coating. The models may also provide insight into common problems associated with these processes. Anticipated benefits: The ability to predict process characteristics from developed models, which will aid in process and quality control. Deepening our understanding of the physics of these processes, and the roles that shear thinning and viscoelasticity play. Student conducting experiment in the Polymer Processing Laboratory