Nonlinear viscoelastic characterization of a linear polyethylene (HDPE) melt in rotational and irrotational flows

Abstract

We analyse the rheology of a commercial linear high-density polyethylene (HDPE) melt with a broad molecular mass distribution in uniaxial, equibiaxial, and planar extension as well as in shear on the basis of a single integral constitutive equation with time/deformation separability. In shear, the HDPE melt is in good approximation a Doi–Edwards (I.A.A) fluid, while in extension, it is a molecular stress function (MSF) fluid with considerable strain hardening. In molecular terms this means that in shear flow, molecules are only orientated, but not stretched, while they are orientated and stretched up to a factor of 5.5 by irrotational flows.