Methods of measuring rheological properties of interfacial layers (Experimental methods of 2D rheology)

Abstract

-Current methods of studying the rheological properties of interfacial layers at the interfaces of fluids are reviewed. This area of research includes two-dimensional 2D rheology. Regardless of the similarities between the parameters of rheological properties of two-dimensional and bulk (three-dimensional) systems, when measuring surface properties, it is necessary to reformulate the main experimental methods to allow for the different dimensions of surface and bulk characteristics of material. Parameters of shear and dilational (measured upon expansion-compression) properties of interfacial layers are distinguished, and the latter are considered to be independent parameters of a system. The most attention was given to the rotational methods of measuring shear viscosity and the components of the complex 2D elastic modulus, as well as to measuring surface tension upon harmonic changes of the bubble (droplet) surface area, which allows characteristics of the dilational behavior of thin liquid films to be determined. Both groups of methods are widely used in laboratory practice and realized in the form of a number of original and commercial instruments. Dilational measurements of interfacial layers can also be performed with oscillations of a movable barrier on a Langmuir trough. In addition, methods based on the propagation of capillary waves across the surface of a liquid, as well as rarer methods of capillary flow in thin channels forced by either a surface tension gradient or the motion of the interface, are considered.

Food grade duplex emulsions designed and stabilised with different osmotic pressures

“…The changes measured in the interfacial tension during oscillations of a droplet surface area were negligible. This is probably a consequence of the PGPR now being at a concentration so that it can cover the interface during expansion therefore loss and storage moduli remained low [21]. It is generally thought, that there is a positive relationship between interfacial rheology and emulsion/foam stability [22] and any factor that tends to strengthen the interactions between adsorbed molecules leads to an increase in the interfacial (shear) viscosity and elasticity [23].…”

Sorption and Interfacial Rheology Study of Model Asphaltene Compounds

“…This is due to its impact on mass transport: the mass flux will be higher near a highly curved interface compared to the planar case. Additionally, for systems in which extra stresses are significant, these effects are unaccounted for in the classical analysis for pendant drop experiments and dilatational rheology measurements 53 .…”

“…The principle behind the oscillating drop is that the interfacial tension varies when the area (A) of a droplet is changed in an oscillatory manner at a given frequency (ω) from an initial ( ) to a value ( ) following equation (4) 53 .…”

IR Studies of Interfacial Interaction of the Succinic Surfactants with Different Head Groups in Highly Concentrated W/O Emulsions

“…The principles of the operation of this instrument are based on the Young-Laplace equation describing the profile of a droplet created by the more dense phase and suspended in the less dense phase. [15] The Young-Laplace equation is the balance between the interfacial tension against gravity: the interfacial tension tending to reduce the interfacial area and gravity tending to increase it by extending a droplet.…”