RHEOLOGICAL STUDIES OF THE GELATION OF AQUEOUS-SOLUTIONS OF ACRYLAMIDE ACRYLIC-ACID COPOLYMERS IN THE PRESENCE OF CHROMIUM CHLORIDE

The gelation kinetics of aqueous solutions of acrylamide-acrylic acid copolymers in the presence of chromium ions was studied with different rheometers. The gel time is found to vary with the principle of the a pparatus because of a low shear dependence of the elongation of the ma cromolecules. The variations of the gel time with the experimental con ditions of the gel preparation were investigated and we conclude that the gelation is governed by the oligomerization kinetics of the chromi um ions which are instantaneously complexated by the carboxylate group s of the polymer. The variation laws of the gel time and of the elasti c modulus with chromium and polymer concentrations, temperature and io nic strength are in qualitative agreement with the structure of the te mporary network of the semi-dilute solutions of these copolymers.