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.

中文翻译：

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毛细管模头前的径向流对挤出 PDMS 行为的影响：速度场-扭曲的股线相关性

目前的工作旨在研究流动几何形状对与线性聚二甲基硅氧烷 (PDMS) 相关的体积不稳定性的影响。为此，在模具入口处产生了会聚径向流。在不稳定流动状态下进行的粒子图像测速 (PIV) 记录，在毛细管流变仪中，以新的入口区为特征，显示出模具上方的新流线模式和在储层角落形成的涡流消失。在模头出口处获得的挤出物股线的照片描绘了一种新的缺陷形态，它出现在一个完善的径向流中。这些结果导致总熔体破裂和入口区流动不稳定性之间的相关性一致。