HIGH VISCOUS STRESS OF ORIENTED POLYOLEFINS UNDER UNIAXIAL TENSILE DEFORMATION

Abstract

In this communication, by means of stress relaxation experiments, the viscous stress at various strains during tensile deformation of oriented polyolefin samples including high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and isotactic polypropylene (iPP), has been determined. The viscous stress in the oriented samples takes up to 50%–70% of the total stress, which is unusually high compared with their isotropic counterparts. The unusual high viscous stress was discussed based on mainly the existence of shish structure in oriented polyolefins, which could enhance the inter-lamella coupling significantly.