Polydispersity effects in polymer transport through porous media

7 Polydispersity effects in polymer transport through porous media 

In order to model polymer transport phenomena of this type, where polydispersity effects are important, it is not adequate to consider the polymer as a single component of concentration, c, as has been done so far in this chapter. The polymer itself is made up of many components which are different only in their size (although the Mark-Houwink parameters that apply for the polymer will be esentially the same for each of the polymer subcomponents). Thus it is necessary to use a multicomponent representation of the polymer molecular weight distribution in order to model the polymer behaviour adequately in such experiments. Brown and Sorbie (1989) have adopted this approach in order to model the Chauveteau-Lecourtier results quantitatively. They used a multicomponent representation of the MWD based on a Wesslau distribution function (Rodriguez, 1983, p. 134) with 26 discrete fractions being used to represent the xanthan. For this case, a set of convection-dispersion equations including dispersion and surface exclusion 

depending on the values of Vi (which depend on a single parameter) and the dispersion, Dj, the concentration and intrinsic viscosity profiles of the effluent can be calculated. This is applied to the Lecourtier-Chauveteau results, and it has been found that the data interpretation in such experiments is complicated somewhat by the presence of dispersion and is discussed more fully by Brown and Sorbie (1989). 

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