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 a ir 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 experimen tally 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) 199 7 Elsevier Science B.V.