consistency (Section 17.2.2) or to provide stability by arresting or slowing
down the diffusion of molecules or the leaking out of liquid (Section 5.2).
Another important function of polymers is tostabilize dispersions.
Polymers in solution can slow down sedimentation and aggregation of
particles, or even prevent these phenomena if they form a gel (Section 13.3).
Many polymers, especially proteins, adsorb onto fluid or solid particles,
thereby greatly affecting colloidal interactions between the particles, hence
their stability. This will be discussed in Sections 10.3.2 and 12.3.1, using
basic aspects given in the present chapter. Polymers in solution can also
cause aggregationof dispersed particles, i.e., instability (Section 12.3.3).
FIGURE6.1 Apparent viscosityðZaÞof polymer solutions of various concentration
(%w/w). Shear rate zero (extrapolated) for xanthan, about 100 s^1 for the other
solutions. (Approximate results after various sources.)