Rheological behavior of fluorinated highly concentrated reverse emulsions with temperature

Reverse highly concentrated fluorinated emulsions exist in a large temperature domain (between 10 and 50 degrees C), The study of the phase behavior reveals that the continuous medium composition varied with the temperature. Highly concentrated emulsions behave as elastic solids. Monitoring the evolution of their elasticity with time as a function of temperature by rheology is an original way to characterize their aging. This method was used to get more insight into the modification of the behavior of polydisperse emulsions 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 independent of its thickness, This coalescence mechanism is thermally activated with an activation energy of 50 k(B)T. (C) 1999 Academic Press.