Flow enhancement in the continuous extrusion of linear low-density polyethylene

Enhanced throughput and the elimination of sharkskin were observed over an extended temperature range when linear low-density polyethylenes having the same molecular weight, polydispersity, and melt index, one with and one wi thout commercial additives, were extruded through alpha -brass dies. The ad ditives appear to play a significant role in the detailed flow behavior, ho wever, most notably in an irreversible transition to a "normal" flow curve at stresses on the order of 0.3 MPa. There are indications of a slip-like p henomenon, including the occurrence of electrostatic charge on the extrudat e. A high-throughput, low-extrusion-pressure processing window like that as sociated by Keller with a transition to a mesophase was observed for the po lymer containing no additives, but not for the polymer containing additives .