Rheological Behavior of Partially Hydrolyzed Polyacrylamide Hydrogel Produced by Chemical Gelation

Hydrogel produced by cross‐linking a dilute or semidilute partially hydrolyzed polyacrylamide solution with water soluble phenolic aldehyde has been characterized by rheology studies. First, the gelation process and the structure of the hydrogel were studied by steady shear flow experiments. Rheological results indicate the gelation process of a dilute HPAM solution includes three stages: a short induction period, an acceleration period and a long termination period. Compared with the polymer solution, cross‐linked hydrogel displays a heterogeneous property owing to the intra and inter‐molecular cross‐links formed during the gelation. Second, the steady state hydrogel properties are discussed as a function of the concentration of both the polymer and the cross‐linker. In contrast, the hydrogel formed in a semidilute regime is more homogeneous than that generated in a dilute regime.