Melt Fracture - Its Consequences for Polymer Processing, Viscosity Measurement and Flow Simulation

Viewers will learn how melt fracture manifests itself as extrudate with a rough and irregular surface when the expectation is that of smooth and defect-free. The capillary rheometer is one of the few instruments which can detect and quantify, via a critical stress value, the phenomenon. Melt fracture has been described by a myriad of terms which serve to confuse an already misunderstood behaviour even more so.
The different terms will be discussed and the authors who coined the terms, in some of their seminal papers, examined for their take on this strange polymer trait which can affect many extrusion disciplines. It will be seen that there is arguably no agreement on the exact mechanism, only on that it exists and when it does so, you usually encounter problems. Melt fracture corrupts the Poiseuille equations of flow about which the capillary rheometer gleans its shear stress, shear viscosity and extensional measurements; how to spot melt fracture in both raw data and the extrudate itself is one of the keys to understanding how to mitigate its effects.
Our Special Guest: Dr. Don Fleming
Fleming Polymer Testing Ltd was established by Dr Don Fleming in 1998 who thus has over 20 years’ experience in the polymer industry. Don graduated in Mechanical Engineering at Bradford University before undertaking a PhD in the same department. The substantive areas of his research were the reactive extrusion of cross-linked LLDPE and PET foams via twin screw extrusion. Having written and presented many papers over the years, juggled with extruder dies, and having his hands burnt on many occasions by a variety of polymer melts, has cemented both the practical and theoretical aspects of rheology.
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