EFFECT OF INTERFACIAL-TENSION AND DROPLET SIZE ON COAGULATION, ADHESION AND RHEOLOGY OF CONCENTRATED EMULSIONS

The thermodynamics of microscopic emulsion films, i.e. the thermodynamics of contact interactions between emulsion droplets with radius R and interfacial tension sigma0, have been systematically analyzed to identify the important role which is played by the deformability of liquid droplets (defined as the ratio v the height PI(b) of the coagulation barrier, or the depths PI1 or PI2 of the near or far coagulation minima of the disjoining pressure isotherm PI(H), respectively, to the capillary pressure P(c) = 2sigma0/R) in the stability, adhesion and rheological properties of highly concentrated emulsions. It has been demonstrated that increasing the parameter v at a constant and relatively high coagulation barrier PI(b) < P(c) (i.e. increasing the droplet size and decreasing sigma0), increases the stability of coagulation of emulsions and decreases the plastic strength P(s) of highly concentrated emulsions. But if the height PI(b) of the coagulation barrier disappears (at sufficiently high electrolyte concentration), then the above mentioned dependences are inverted, i.e. the aggregative stability of emulsions decreases and P(s) increases with increasing v i.e. with increasing R and decreasing sigma0.