Coalescence in emulsions

Content uniformity and long-term stability of a pharmaceutical product are required for a consistent and accurate dosing. Aggregation of dispersed particles and resulting instabilities such as flocculation, sedimentation (in suspensions), or creaming and coalescence (in emulsions) often represent major problems in formulating pharmaceutical disperse systems. 

Partial Coalescence in Emulsions Comprising Partially Crystallized Droplets 167... 

Formation of spray in small drops (i.e. 30 microns, with a narrow size distribution) using a rotary disc or nozzle, to enhance the product-air interface. The preparation of the feed (dry matter content, composition, temperature, mixing) must facilitate pumping and spraying with minimal modification (partition of constituents, droplet coalescence in emulsions). 

Jaeger Ph.T., Janssen J.J.M., Groeneweg F., Agterof W.G.M., Coalescence in emulsions containing inviscid drops with h interfadal mobility. Colloids Surfaces A Physicochem. Eng. Aspects 85 (1994J, p. 255-264... 

Sjoblom J, Foredal H, Skodvin T. Flocculation and coalescence in emulsions as studied by dielectric spectroscopy. In Ref. 1 393-435. 

The method employed to obtain the results of Figure 13.17, i.e., determination of average droplet size as a function of time, is quite suitable to establish the rate of coalescence in emulsions. It may even be better to... 

Coalescence in emulsions, with an emphasis on engineering applications, is in A. K. Chesters. Coalescence Probability. Trans. Inst. Chem. Eng. 69 (1991) 259-270. Useful information is also in the textbook... 

Finally, it is worthwhile noting that the simultaneous flocculation and coalescence in emulsions could be also accompanied with adsorption of amphiphilic molecules on the drop surfaces (195) this possibility should be kept in mind when interpreting experimental data. 

KD Danov, IB Ivanov. Critical film thickness and coalescence in emulsions. Proceedings of the Second World Congress on Emulsions, Paris, 1997, Paper No. 2-3-154. 

Kabalnov, A.S. (1998) Coalescence in emulsions. In B.P. Binks (ed.). Modern Aspects of Emulsion Science. The Royal Society of Chemistry, Cambridge, UK, Chapter 7. 

Hi denotes the number of single particles per unit volume rij is the number of aggregates of k particles (k=2,3,...) per unit volume ay (i, j = 1, 2, 3,. ..) are rate constants of flocculation (coagulation see Figure 4.65) qi denotes the flux of aggregates of size k which are products of other processes, different from the flocculation itself (say, the reverse process of aggregate disassembly or the droplet coalescence in emulsions see Equations 4.346 and 4.350)... 

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