GELATION KINETICS AND RHEOLOGY OF METAL-ION-CROSSLINKED POLYMER SOLUTIONS.

Polyacrylamide and guar polymer solutions can be crosslinked with transition metal ions. The resulting gels are used to alter the permeability of porous media in enhanced oil recovery processes, and as fracturing fluids in oil well stimulation processes. The kinetics of the formation of the gel network can be determined from the time dependence of the storage modulus of the gel during crosslinking. The results are interpreted using polymer network theory to relate the measured storage modulus to the number density of crosslinks. The effect of solution ionic strength on the rate of reaction for polyacrylamide/Cr(III) gels is explained in terms of electrostatic interactions between polymer chain segments.