Pearling Instabilities of a Viscoelastic Thread

Area of Science:

• Fluid dynamics
• Polymer science
• Rheology

Background:

• Pearling instabilities in viscoelastic threads are complex and not fully understood.
• These instabilities are crucial in processes involving polymer solutions under flow.

Purpose of the Study:

• To investigate the mechanisms behind pearling instabilities in polymer solutions during uniaxial elongational flow.
• To differentiate between capillary-driven and stress-coupled instabilities.

Main Methods:

• Subjecting polymer solutions to uniaxial elongational flow.
• Observing and characterizing different instability structures (beads-on-a-string, blistering).
• Varying temperature to alter solution properties and study flow-phase separation interplay.

Main Results:

• Two distinct instabilities were identified: beads-on-a-string and blistering.
• The beads-on-a-string instability is attributed to capillary forces.
• The blistering instability originates from a coupling between stress and polymer concentration.

Conclusions:

• The study elucidates the distinct origins of different pearling instabilities in viscoelastic threads.
• It highlights the role of stress-polymer concentration coupling in blistering instability.
• Temperature-dependent analysis reveals the interplay between flow and phase separation in polymer solutions.