Effect of surfactant concentration and operating temperature on the drop size distribution of silicon oil water dispersion

The effect of sodium lauryl sulphate (SLES) surfactant and the operating temperature on the drop size distribution of a 350 cSt Dow Corning 200 series oil water dispersion was successfully studied. The dispersion was prepared in a standard 6 litres mixing tank at different impeller speeds. A measurement of the SLES critical micelle concentration (CMC) at 25 degrees C was carried out. The interfacial tension of silicon oil water under various SLES concentration at a temperature range of 25 to 80 degrees C was accomplished. Results showed that the interfacial tension of the silicon oil water decreased as the operating temperature increased and as the surfactant concentration increased. When the operating temperature was increased at the highest SLES concentration tested, a decrease of d(32) was observed. This was attributed to the possibility of hydration of the surfactant at high temperature. Same behavior was observed when measuring the drop size distribution at constant temperature but different SLES concentration. It was found that the mean drop size decreases with mixing time. Different slopes of the change of the median drop size with time were obtained for different SLES concentration. For the same concentration, the slope changes after 1 hour. The degree change of the slope is due to the change of interfacial area of the oil water as mixing time elapsed and the depletion of the surfactant concentration.