Common line motion .3. Implications in polymer extrusion

This paper is the third in a series of papers in which we examine both theoretically and experimentally the motion of the common line (three-phase line of contact) formed by a deforming viscoelastic fluid and air on a solid surface and its role in polymer extrusion. In this paper, the wetting behavior in the exit region of a die are shown experimentally to be responsible for the onset of the sharkskin instability in the LLDPE extrusion. The results of parts I and II are used to suggest a mechanism for the instability. Die drool is also discussed. (C) 1997 Elsevier Science B.V.