Elongational Behaviour of Dilute Polymer Solutions

Abstract

Experimental results concerned with the elongational behaviour of dilute polymer solutions were presented. The elongational viscosity was measured as a function of the strain rate for an aqueous solution of the neutral polymer PAA-T19 and for an aqueous 0.2 mol/1 XaCl solution of the ionic polymer Sedipur AF 701. Flow induced birefringence was monitored simultaneously in order to assess the orientation of the polymer molecules. A critical strain rate i* depending on the type of polymer solution separates two flow regions: a Newtonian region of strain independent elongational viscosity and a region with markedly and continuously increasing elongational viscosity. Calculations applying the FENE dumbbell model were shown to be in good accordance with the experimental results of the non-ionic solution. Experimental data for the pipe friction factor λ as a function of the Re number are presented for both solutions and are discussed in connection with the elongational viscosity results.