The use of large transient deformations to elucidate structural phenomena and evaluate network models for molten polymers /

That some kind of network plays a central role in the rheology of high molecular weight, amorphous polymers is inferred from such phenomena as a change in the slope of the curve of viscosity versus molecular weight and the plateau in the stress relaxation curve. However, these data give no explicit information about the rates of network destruction and reformation. A new method which involves the reduction in shear rate in transient shearing flow was used to obtain such network kinetics information for three polyethylene melts at 170(DEGREES)C.Other methods of characterization have also been used. These include steady simple shear, small amplitude oscillatory shear, large amplitude oscillatory shear and transient uniaxial extensional flow. All of the above methods involve different types of deformation in both linear and nonlinear viscoelastic regions. These data were used to test the predictive abilities of two constitutive equations inspired by network theory