Recent Experimental Aspects of Non-Linear Viscoelasticity

Abstract

Hereunder is presented a review of recent experimental studies made on the non-linear viscoelasticity of polymer solutions and melts. The subjects covered are:(1) Non-Newtonian viscosity behavior of narrow-distribution polymers, (2) the normal stress effect in steady shear flow, (3) the recoverable strain in steady shear flow, (4) the stress relaxation after the cessation or interruption of steady shear flow, (5) the growth of stress after the onset of the steady shear flow, (6) the recoverable strain during the approach to the steady shear flow, (7) the sinusoidal oscillation superimposed on the steady shear flow, and (8) the stress relaxation under larger shear strain. It is specially noted that the distribution function of relaxation time obtained with a constant rate of deformation is appreciably shifted to be made on short time scale, depending on the deformation rate, while the distribution function obtained with a constant deformation is not. Emphasis is also put on the key role of the recoverable strain measurements in the study of non-linear viscoelasticity.