Non Isothermal Flow Dynamics and Viscous Heat Generation in Polymer Melt Extrusion
Non-isothermal viscous dissipation drives core melt temperature spikes that cause extrudate defects if die land geometry is not scaled to shear rates.
Polymer Melt Extrusion
Meaning
Manufacturing processes that force molten plastic through a shaped die enable the continuous production of uniform profiles and components. In polymer melt extrusion, raw plastic in the form of pellets or powder is heated and pressurized by a rotating screw. This method is the foundation for creating pipes, sheets, films and insulation for electrical wires.
Material Transformation
Solid resin enters the system and undergoes a transition into a viscous liquid through a combination of external heat and internal friction. The polymer melt extrusion process requires precise control of the temperature profile along the barrel to prevent degradation. Each zone of the machine serves a specific purpose in melting and mixing the material.
Barrel Performance
The capability of the system is measured by its ability to deliver a stable flow of plastic at a constant pressure. Within polymer melt extrusion, the screw design must match the specific rheology of the resin being used. If the barrel is too short, the melt may contain un-melted particles that ruin the surface of the final product.
System Throughput
Output rates are determined by the screw speed and the resistance of the die at the end of the line. A supplier forecast for polymer melt extrusion often assumes ideal conditions, but the demonstrated rate depends on the cooling capacity of the downstream equipment. Increasing the speed without adequate cooling results in dimensional instability.