Mechanism of emulsion flocculation

This can occur if the energy barrier is small or absent (for electrostatically stabilised emulsions) or when the stabilising chains reach poor solvency (for sterically stabilised emulsions, i.e. x 0-5). For convenience, I will discuss the flocculation of electrostatically and sterically stabilised emulsions separately. 

As discussed in the section on physical chemistry of emulsion systems, the condition for kinetic stability is Gmax 25kT when G ax 5kT, flocculation occurs. Two types of flocculation kinetics may be distinguished Fast flocculation with no energy barrier and slow flocculation when an energy barrier exists. 

Fast flocculation kinetics have been treated by Smoluchowski [32], who considered the process to be represented by second-order kinetics and the process is simply diffusion controlled. The number of particles n at any time t may be related to the initial number (at t = 0) no by the following expression, 

The half-life ti/2 n = j o) can be calculated at various no or volume fraction as give in Table 6.6. 

Slow flocculation kinetics have been treated by Fuchs [33] who related the rate constant k to the Smoluchowski rate by the stability constant W, 

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