Melt Flow Instabilities in Polyethylene Resins¹

Yang Chen, Wei Luo, Yi Li, Huawei Zou*, Mei Liang**, and Ya Cao

The State Key Lab of Polymer Materials Engineering, Polymer Research Institute of Sichuan University,
Chengdu, 610065 China

*e-mail: hwzou@163.com

**e-mail: liangmeiww@163.com

Received November 19, 2013;
Revised Manuscript Received February 10, 2014

Abstract—The melt flow instabilities of four polyethylene (PE) pipe resins were investigated and critically
compared. By comparing the flow curve obtained by capillary rheology measurements with the linear viscoelas-
tic (LVE) data, the apparent slip was seen in the four polyethylenes. It was proposed that the high content of
small chains could cause the significant wall slip, but the slip was not the origin mechanism of shark-skin melt
fracture. The bimodal resins that had higher content of low molecular weight component first showed a matte
surface at lower stresses. The matte surface remained until the extrudate converted to a wavy appearance as
shear rates were increased. It was observed that the onset stress of sharkskin melt fracture was almost propor-
tional to the plateau modulus. Furthermore, the chain relaxation time of the resins also influences the surface
melt fracture behavior of the resin.

DOI: 10.1134/S0965545X1405006X

Pleiades Publishing home page | journal home page | top

If you have any problems with this server, contact webmaster.