Flocculated network

Sonntag, R.C., and Russel, W.B. (1987). Elastic properties of flocculated networks. Journal of Colloid and Interface Science. 116 485 89. 

The process of the formation of flocculated networks of dispersed particles or phases in heterogeneous polymer systems consists of various elements [72e,37,89,90], which need to be understood before looking at the simulations ... 

We will start with the observations At the critical concentration, conductivity jumps over several orders of magnitude, and the flocculated network structures can be observed under the scanning electron microscope. 

In contrast to expectations of most scientists, dispersion does not lead to a deterioration of the conductivity properties (by, e.g., new barriers from the dispersion matrix), but to an improvement. This implies that during the dispersion process, barriers must have been reduced, and possibly the arrangement of the particles in relation to each other (in the flocculated network) is optimized with regard to the tunneling process. 

Microgels thicken paint by forming flocculated network structures. In solvent-borne systems they are not insensitive to solvent selection, but are much less sensitive and are effective in polar organic solvents. Indeed, swelling of the polymer particles by solvent enhances their effect, by increasing particle diameter and hence increasing the apparent gel volume. 

After passing through a certain critical temperature the specific resistance begins to show a marked reduction. This can be attributed to increased formation of flocculated network structures at increased temperature. Figure 19.36 shows this situation in terms of the... 

Sonntag RC, Russel WB (1987) Elastic properities of flocculated networks. J Colloid Interface Sci 116(2) 485... 

This behaviour may be interpreted as indicating the presence of a flocculated network. Each droplet is presumed to be in contact with two or more neighbouring droplets, and the resultant network creams by a compaction mechanism. The individual droplets do not coalesce if a sample is removed from the emulsion and diluted for sizing, the original droplet size distribution is obtained. 

The reasons for the delay are not yet well established, but a possible explanation invokes a yield stress in the flocculated network. The inter-droplet attraction is presumed to be strong enough to hold the droplets in the structure. However, we speculate that the droplets in the flocculated network are continually rearranging to form more compact structures, and that after a certain time, the delay period, the... 

Figure 4.11 Volume finction profiles during creaming of an emulsion with 0.04% hydroxy-ethylcellulose (HEC), showing a flocculated network...

Figure 4.12 Creaming of emulsion with 0.95% hydroxyethylcellulose. (a) Volume fraction profiles showing a flocculated network, (b) Height of the base of the network with time, showing delay period...

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