2. The effect of temperature on interfacial tension (and hence coalescence).
The interfacial tension is reduced as the temperature
increases [2], and this promotes coalescence. Again, this effect is
more marked in the low-water emulsions due to higher temperatures
in the water phase.
3. Other temperature effects. The probability of coalescence is not
only a function of interfacial tension, but also droplet size distribution,
number of droplets and dispersion density. Since those
parameters were not constant across the different starting
emulsions, the effect of different temperature profiles on each
emulsion is difficult to predict.
4. Effect of droplet size on dielectric properties. The droplet size
has been shown to affect the dielectric properties of emulsions.
Holtze et al. [3] reported a peak in dielectric properties for
water-in-oil emulsions somewhere between 3.6 lm and
>10 lm mean droplet diameter. Although more data would be
required on the specific emulsions used in this study, it is possible
that microwaves heat the lower water content emulsions
more effectively due to their smaller droplet size.