Non-Newtonian Flow of Structured Systems. IX. The Elasticity of Polymer Solutions

Abstract
The structural rheological model to describe the elastic properties of polymer solutions under steady state flow is proposed. The new equation is used for the first normal stress differenceN₁. This equation of elasticity similar to generalized flow equation and describes experimental dependence

at high shear rates. The first term is a structural part of the elasticity due to associates of macromolecules. The second part describes the own elasticity of individual macromolecules. Structural rheological model predicts a linear dependence N₁ of the shear rate

at low shear rates. Experimental results demonstrate the dependence

, and the magnitude ΔN₁ can have both positive and negative. Appearance in this equation values ΔN₁ may be due to a systematic error in the measurement of the elastic forces. Popular rheological models predict different behavior of N₁, namely, the quadratic dependence.

Keywords: viscoelastic systems, polymer solutions, structural rheological model, first normal stress difference, equation of elasticity