NON-NEWTONIAN FLOW OF STRUCTURED SYSTEMS. XXVII. VISCOSITY AND ELASTICITY OF POLYISOBUTYLENE SOLUTION
Rheological properties of Standard Reference Material® (SRM) 2490, which is a non-Newtonian fluid consisting of polyisobutylene dissolved in 2,6,10,14-tetramethylpentadecane, are described by a structural rheological model. The viscosity h and the first normal stress difference N<sub>1</sub>, as well as the viscoelastic storage modulus G' and the loss modulus G" were described by the equations of the structural rheological model. These equations are different in the region of low shear rates (low cyclic frequencies) and in the region of high shear rates (high cyclic frequencies), which is due to the different state of the fluid structure. The temperature dependence of the coefficients of rheological equations and the relationship between the structural part of viscosity and the structural part of elasticity have been established.