Chapter 2
proposed by Einstein from hydrodynamic considerations on suspensions of hard
spheres [9L [10]:
77 = 77c(l + ^)
[2.2]
Here K = 1-2.5 is a constant and φ is the dispersed phase content.
For emulsions with higher dispersed phase content, one corrected equation
is [11]:
z ∖2.49
1 φ∕‰ I
[2.3]
η = ηr I +--- ---
' lc{ l.!87-φ∕‰J
Here фюо is the dispersed phase content at ηlr∣c = 100 which is measured
experimentally.
Another important factor is the mean drop size. Friction between droplets is
related to the interfacial area and therefore increases viscosity when the
surface-to-volume ratio of the dispersed phase increases [12]. Thus an emulsion
with smaller mean drop size should exhibit higher apparent viscosity than another
with higher mean drop size.
2.3. Emulsion stability
2.3.1. Interaction forces
The most often referred to mechanism in emulsion literature to explain
emulsion interaction is the so-called DLVO theory, developed independently by