Extensional flow phenomena in polymer solutions

The objective of the present work was to develop techniques for establishing uniaxial extensional flow and to use these techniques to study the extensional flow response of polymer solutions. To this end, an elongation drop apparatus was built in which either the extension, rate or the imposed stress could be controlled. A Newtonian silicone oil and two viscoelastic polymer solutions (10% polyisobutylene in Decalin(PIB) and 2.8% Separan AP 30 in 50:50 glycerol-water solution(PAA)) were tested in both stress growth (controlled extension rate) and approximate creep (controlled stress) experiments. Viscometric flow measurements were also performed on the polymer solutions using the Weissenberg Rheogoniometer. Extensional flow tests with the Newtonian silicone oil established the capabilities of the drop elongation apparatus. The prescribed responses in both stress growth and approximate creep experiments were reached within a time period of less than one second. The steady extensional viscosities obtained from both experiments were in good agreement with Trouton's law. [...]