Effect of die surface on the onset of stick-slip transition in the flow of molten linear polymers

We develop a relationship to describe the effect of surface roughness on the stick-slip transition for linear polymers. Using the Brochard-de Gennes slip model and including molecular chain dynamics at the wall, we develop an expression for the critical shear stress for the onset of wall slip as a function of the wettability of the polymer on the die surface or, more precisely, as a function of the apparent contact angle between polymer and die surface. The surface roughness can be also accounted for using additional parameters. (C) 2011 Elsevier B.V. All rights reserved.