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Trumpet flow geometry to postpone volumic defects

It has been shown that the use of a smooth convergent geometry was very efficient to postpone the volume defects encountered in polystyrene extrusion. Instead of a flat entry, a small angle (30°, 45°) or even best a smooth profile (trumpet-shape profile) permits to increase the flow rate by a factor 8 before the onset of any volume instability. This effect was also observed for the polypropylene. By using numerical simulation, it has been evidenced that the stress field was highly modified by the reduction of the entry angle and that the use of a trumpet-shape profile allowed one to largely reduce the extensional stresses at the entry of the die channel.

Reported by

CEMEF, Ecole des Mines de Paris
Rue Claude DAUNESSE BP 207