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The flow of viscoelastic fluids in an opposed jets rheometer and a Fano flow rheometer

Wilkes C., Gampert B.

International Journal of Applied Mechanics and Engineering

2003

Vol. 8, no spec.

319-324

The elongational rheometer used for this work is an opposed jet rheometer, which allows elongational flow measurements of highly dilute polymer solutions. The polymer concentrations can be lower than the critical concentration under steady state conditions and lower than the critical concentration in the case of flow conditions. A further experimental set up was used for characterising the viscoelastic fluids. The working method of this apparatus is the tubeless siphon or Fano flow, which can be understood approximately as the reverse fibre spinning process. The beginning of the fibre spinning process can be applied in order to determine the critical concentration . The experimental investigations undertaken here were carried out using a commercial, anionic polyacrylamide with a relatively high molar mass and hydrolysis factor. The polyacrylamide was dissolved in highly pure water. Sodium chloride with different concentrations was added to the solutions to control the partial neutralisation of negative charges at the ends of the polymer chains.

The influence of the ionic strengths of polyacrylamide and xanthan gum

Gampert B., Wilkes C.

Applied Mechanics and Engineering

1999

Vol. 4, no spec.

283-288

Polyelectrolytes are macromolecules which carry a large quantity of ionizable groups along their chains. By dissolving them in suitable solvents, for example water, these groups dissociate in highly charged macroions and an equivalent quantity of low molecular counter ions. Through the bonding of polymer and electrolyte properties this class of materials obtains its peculiar characteristic behaviour. For the characterization of phenomenological effects of polyelectrolyte solutions, viscometric and conductometric methods will be applied for this paper. There, the viscosity measurements will be carried out using highly dilute polymer concentrations where the intermolecular interactions play a role. The experiments undertaken here were carried out using a commercial, anionic polyacrylamide and xanthan gum with different hydrolysis factors and molecular weights. The reduced viscosity increases strongly with the decrease of polymer concentration for low cp values. It reaches a maximum and then decreases again.