Coalescence of polymer droplets: experiments on collision

Abstract

The coalescence of polymer droplets is a fundamental phenomenon which appears for example when mixing two polymers. When Two polymeric droplets collide, a transient regime appears, which results from a competition between interfacial and viscoelastic effects: the spherical droplets deform to give birth to a new drop in a short time (t(c)) and the drop shape stabilizes after a long time.A new method is proposed to study experimentally under a microscope the collision between two droplets of polymer, with different viscosity ratios. This allows to determine the characteristic time t(c) which defines this phenomenon. The experiments actually show that t(c) varies like the geometric mean of the viscosities of the two polymers, for the case of a polydimethylsiloxane/polyisobutylene system. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.