A kinetic network model for nonlinear flow behavior of molten plastics in both shear and extension

The revised Berkeley kinetic network model is shown to accurately describe experimental data in many types of nonlinear deformation, including large amplitude oscillatory shear (LAOS), exponential shear, planar extension, step biaxial extension, uniaxial extension, and step strain, for the IUPAC X low density polyethylene (LDPE). It is shown that while LAOS is helpful in determining the approximate model parameters, a LAOS test is not sufficient to determine their precise values. Exponential shear, however, is more sensitive to the parameter values, and LAOS and exponential shear together are sufficient for precise parameter determination. Both of these experiments can be performed easily on a sliding plate rheometer incorporating a shear stress transducer. (C) 1997 Elsevier Science B.V.