Fourier Transformation Analysis in Capillary Flow—A New Option to Detect Flow Instabilities (Shark Skin)

Abstract

Flow instabilities cause various problems in extrusion blow-or flat film processes. Especially shark skin is affected by molecular structure. This phenomenon is analyzed in various scientific works using apparatus that are complex or difficult in operation. A new set-up, now available is being presented as an option for new and existing capillary rheometers or lab extruders, consisting of a special designed die, a fast responsive transducers system and evaluation software. The software allows the evaluation of diverse pressure frequency regimes causing flow instabilities and generate statistics. Measurement examples are given for different shear rates and polymers. The shark skin effect can be detected even before it is visible on the extrudate. The measured frequency regimes are related to molecular parameters

Rheological characterization of polyolefin composites with reduced flammability

“…The aim of this study is to show how the non-conventional rheological die Shark skin 5 can be helpful to characterize the filled melts when other techniques fail.…”