Capillary thinning of filaments of polymer solutions with surfactants

We present an investigation of the influence of a surfactant content on the rheological behaviour of aqueous solutions of a flexible polyacrylamide in strong uniaxial elongational flow. The flow is produced by the capillary thinning of a liquid filament in an elongational rheometer. Measurement data consist in the temporal evolution of the filament diameter. The data is interpreted in the light of a theoretical analysis, which assumes that the surfactant causes the relaxation time of the solution to become time dependent, which is due to scission and formation of micelles in the solution on a certain time scale. The evaluation of the experimental results allows for determination of this time scale and leads to conclusions about its consequences on the rheological behaviour of these solutions.