Effect of die exit geometry on internal die drool phenomenon during linear HDPE melt extrusion

Abstract

In this work, the effect of die exit design on the internal die drool phenomenon occurring during extrusion of HDPE has been experimentally investigated. It has been revealed, that firstly, the effect of flared length and die exit angle on the internal die drool intensity during extrusion of HDPE has non-monotonic character and secondly, flared dies are more stabilizing in comparison with chamfered dies. It has been suggested that suppression mechanism of the internal die drool phenomenon through die exit modification can be understood through the balance between the melt pressure/normal stresses at the die exit, adhesion at metal wall/flowing melt interface and extensional stress induced by the extrudate draw off, which can lead to flow situation at which low molecular weight species are effectively removed from the die exit region by the moving extrudate and only small portion of them remains at the die exit face. © 2012 Elsevier Ltd. All rights reserved.