Rheological behavior of fluorinated highly concentrated reverse emulsions with temperature

Reverse highly concentrated fluorinated emulsions exist in a large temperat ure domain (between 10 and 50 degrees C), The study of the phase behavior r eveals that the continuous medium composition varied with the temperature. Highly concentrated emulsions behave as elastic solids. Monitoring the evol ution of their elasticity with time as a function of temperature by rheolog y is an original way to characterize their aging. This method was used to g et more insight into the modification of the behavior of polydisperse emuls ions with temperature and time. The elastic modulus decreased exponentially with time in the range of temperatures studied. This was interpreted as a result of coalescence due to a single film rupture frequency which was inde pendent of its thickness, This coalescence mechanism is thermally activated with an activation energy of 50 k(B)T. (C) 1999 Academic Press.