Understanding droplet coalescence and its use to measure interfacial tension

Claude Verdier (1) , Matthieu Brizard (1)

1 LR - Laboratoire de rhéologie

The study of coalescence of polymer droplets is presented, in the viscosity ratio range (p) going from 0.1 to 10. It is shown that the determination of the characteristic time of collision is a good way to have access to the interfacial tension. Polydimethylsiloxane (PDMS) is mixed with Polyisobutylene (PIB) and the temperature change provides a way to modify the interfacial tension of the PDMS/PIB system significantly, as measured using a pendant drop apparatus. We obtain a dependence of the reduced collision time as a function of p^-1/2 which gives access to the interfacial tension. This technique can be an interesting choice for measuring interfacial tension without requiring sophisticated techniques. In a further attempt to correlate these observations with a theoretical model [Verdier C., Polymer, 42, 2001], the flow field inside and outside the droplets is investigated. PIV measurements are carried out where the evidence of elongational regimes is demonstrated. Such experiments are also interesting for future comparisons with numerical results.

Mots clés: collision; polymer; elongation; viscosity ratio; PIV

Domaines: Mécanique des fluides [physics.class-ph]

Claude Verdier, Matthieu Brizard. Understanding droplet coalescence and its use to measure interfacial tension. Rheologica Acta, 2002, 41, pp.514-523. ⟨10.1007/s00397-002-0249-8⟩. ⟨hal-00322106⟩