Coalescence of polymer droplets: experiments on collision
نویسندگان
چکیده
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 (tc) and the drop shape stabilizes after a long time. A novel method is proposed to study experimentally under a microscope the collision between two droplets of one polymer in another one, with different viscosity ratios. This allows to determine the characteristic time tc which defines this phenomenon. The experiments actually show that tc varies like the geometric mean of the viscosities of the two polymers, for the case of a polydimethylsiloxane/polyisobutylene system. Coalescence de gouttelettes de polymères : expériences de collision Résumé La coalescence de gouttelettes de polymères est un phénomène fondamental qui intervient par exemple lorsque l’on mélange deux polymères. Lorsque deux gouttelettes de polymères rentrent en collision, un régime transitoire apparaît, qui est régi par la compétition entre les effets de surface et les effets viscoélastiques : les gouttelettes sphériques se déforment pour donner naissance à une nouvelle goutte dans un temps rapide (tc) et la forme de cette goutte se stabilise dans un temps long. Une nouvelle méthode est proposée pour étudier expérimentalement sous microscope la collision de deux gouttelettes d'un polymère dans un autre en faisant varier le rapport des viscosités. Ceci permet d'avoir accès au temps caractéristique tc qui définit le phénomène. Les expériences montrent que tc est en fait proportionnel à la moyenne géométrique des viscosités des deux polymères, dans le cas d'un système polydiméthylsiloxane/polyisobutylène.
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