Patent ID: 8613217

Claim:
A method for determining the dynamic interfacial tension of a surfactant between two liquids, comprising the following steps: flowing a first liquid, the internal liquid (Li), in an internal flow member ( 2 ); flowing a second liquid, the external liquid (Le), in an external flow member ( 4 ); and, adding a surfactant to the one and/or the other of the first and second liquids; wherein the respective internal and external flow members are coaxial and the internal member opens into the internal volume of the external flow member; forming droplets (G) of the internal liquid, in a carrier phase (P) formed by the external liquid, downstream of the outlet ( 2 ′) of the internal flow member in the external flow member, under conditions set for a plurality of values of flow rate (Qe), the flow rate of the external liquid; and determining the value of time (t) of formation of these droplets; subsequently varying the internal flow rate (Qi); and after identifying a transition value of the internal flow rate above which a continuous jet of the internal liquid is then formed in the external liquid, deducing therefrom a value of the interfacial tension (γ) between these two liquids; and producing a curve representing the variation of the interfacial tension value as a function of the droplet formation time; and identifying a characteristic time (t k ) of the surfactant, corresponding to the transition between a first zone (I) in which the value of the interfacial tension is approximately constant as a function of the droplet formation time and a second zone (II) in which this value of the interfacial tension increases as this formation time decreases.