Effect of die design on die drool phenomenon for metallocene based LLDPE: Theoretical and experimental investigation

Abstract

The effect of die design on the die drool phenomenon was investigated for metallocene based LLDPE. It has been found that die exit opening and the flared die design can significantly reduce the die drool phenomenon. Moreover, theoretical research has revealed that die drool onset can be explained by the negative/nonmonotonic pressure profile generated inside the die and/or at the die exit region.

Investigation of Internal Die Drool Phenomenon for Different HDPEs

“…As shown in [4][5][6][7][8][9], formation of die drool phenomenon is influenced by several factors like low molecular fractions of the polymer and its structure, volatiles, die swell, die design etc. However, serious research about the die drool phenomenon for HDPE polymers has not been performed yet.…”

Historical review of die drool phenomenon during plastics extrusion

“…Chaloupková and Zatloukal [13] in 2009 mathematically modelled polymer melt flow in die outlet zone and they disclosed area of negative pressure near the die exit edge contributing to material separation from the matrix. Further, they concluded that negative pressure is crucial important variable for die drool phenomenon.…”

“…This reduction author attributes to a decrease in the work of adhesion which is related to the surface energies of the die-wall material and the polymer melt. Another contribution contains chamfer of the die exit edge [13]. Surprisingly, if the chamfered die exit edge angle is 45° accumulated drool mass is then dramatically reduced.…”

“…However, it should be noticed that this reduction is possible only for certain polymers drooling externally (e.g. metallocene based LLDPE [13,24] or polypropylene [25] polymer melts). "External die drool" is related only to die exit region not to whole flow channel in the extrusion die.…”

Experimental Investigation of Die Drool and Slip-stick Phenomena during HDPE Polymer Melt Extrusion

“…can be found in open literature [4][5][6][7][8][9][10]. Further, three recently published works are focused on die drool phenomenon during HDPE extrusion.…”