Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 7: POSTERS Rheology

CPP 7.2: Poster

Montag, 25. Februar 2008, 16:45–19:00, Poster A

Deviation from elongational flow in the capillary breakup of polyethylene oxide solutions — •Rainer Sattler and Christian Wagner — Campus, Gebäude E2 6 3.OG, 66041 Saarbrücken

The formation of the beads-on-a-string structure on a thinning thread of an elastic liquid is revisited. This structure occurs as previously shown in consequence of a linear instability. However, the evolution has been examined in more detail to evaluate existing iterative concepts and gain more insight into the processes involved. The reported formation of a solidified polymer thread during the final stages of the breakup could be deduced in-situ in an indirect way compared to the Scanning Electron Microscopy images previously presented. Two independent observations allow for a qualitative and quantitative prediction of it matching the known results.

More insight is given on the evaluation of the linear instability justifying the special Super-Resolution method. Singular occurrences of droplets on the fiber prior to the linear instability are discussed. Finally we put emphasis on the examination of the flow conditions within the liquid column from the formation of the cylindrical thread until the onset of the linear instability, falsifying the assumption of a purely elongational plug flow. We present its scope as well as the transition to a flow containing shear and even flow reversal between surface and core especially during the "breathing" instability of the fringe region presented elsewhere.