Stress relaxation upon cessation of steady flow and the overshoot effect of polymer solutions

Abstract

Abstract The basis for obtaining the steady‐state compliance from stress relaxation upon cessation of steady flow (SRUCSF) data is derived. Measurements on three polymer solutions of differing molecular weight, polydispersity, and degree of entanglement coupling show good agreement between results from SRUCSF and creep‐recovery experiments in both linear and nonlinear viscoelastic regions. The stress overshoot phenomenon is interpreted in terms of a change in entanglement spacing upon imposition of a shearing field. The phenomenon is analyzed in terms of a relaxation time for re‐entanglement, which is found to be much longer than the relaxation time of the shear stress upon cessation of steady flow.