LAUSR

The present work aimed to investigate the influence of flow geometry on volume instability associated to a linear polydimethylsiloxane (PDMS). To do so, a convergent radial flow was created at the die entrance. The performed particle image velocimetry (PIV) recordings under unstable flow regime, in capillary rheometer, characterized by the new entrance zone, show a new pattern of streamlines above the die and a disappearance of the vortex developed in the corner of the reservoir. Photographs of the extrudate strands obtained at the die exit depict a new morphology of defect which appears with a well-established radial flow. These results led to the correlation agreement between the gross melt fracture and the flow instability at the entrance zone. It also proved the importance of elongational and shear components linked to the upstream flow in the appearance and development of volume distortion.