Control of the sharkskin instability in the extrusion of polymer melts using induced temperature gradients

The effect of temperature gradients on the sharkskin surface instability in polymer extrusion through a slit die

The sharkskin surface instability is commonly observed in the extrusion of polymer melts. We present a series of experiments in which a specifically designed rectangular slit die with insulated and independently heated sides and is used to induce precise temperature gradients across a flowing polyethylene melt. Our previous experiments demonstrated that the character of the surface distortions ...

Wall Slip and Boundary Effects in Polymer Shear Flows

Polymer – surface interactions strongly influence many important industrial and rheological flows. In particular, polymer melts and solutions slip against the surface; this has long been associated with sharkskin and spurt in extrusion, and recent experimental observations suggest that slip also plays a role in the formation of enhanced concentration fluctuations in entangled polymer solutions....

Analysis and Suppression of Instabilities in Viscoelastic Flows

The viscoelastic character of polymer solutions and melts gives rise to instabilities that are not seen in the flows of Newtonian liquids. In industrial applications such as coating and extrusion, these so-called “elastic” instabilities can impose a limitation on the throughput. Hence, it is important to understand, and if possible, to suppress them. The first instability we study is the phenom...

comparison between to versions of the SAFT EOS in the study of PVT and VLE phase behavior of pure polymer melts and binary polymer solutions

The Occurrence of Periodic Distortions in the Extrusion of Polymeric Melts. Part 1: Modelling and Numerical Results

In the extrusion of polymeric melts at high ow rates, often ow instabilities observed as surface distortions of the extrudate occur. The ow instability 'spurt' in piston-driven ows is accompanied by persistent oscillations in the pressure. In this paper spurt is explained in terms of constitutive instabilities (mechanical failure of the polymeric uid itself), while the no-slip boundary conditio...