Studying the Collapse of Bentonite-Containing Composites Based on Acrylic Copolymers

Abstract

Polymeric polyelectrolyte hydrogel composites based on a copolymer of acrylic acid and acrylamide are synthesized. The composites are filled with bentonite (1 to 5 wt %). The kinetics of the collapse of hydrogel composites in aqueous solutions of salts of alkali and alkaline-earth metals at a constant temperature of 25°C are studied. Gravimetry is used to study the kinetics of the swelling and collapse of a gel of the cross-linked copolymer of acrylic acid and acrylamide, and its composites with bentonite in aqueous solutions of salts of mono- and divalent metals. It is found that the presence of bentonite prevents the collapse of composites based on acrylic hydrogels in aqueous solutions of electrolytes, due to the steric and electrostatic interactions between filler particles. By comparing these two kinetic models, it is shown that Peleg’s kinetic model best describes the experimental data on the collapse of the polymer hydrogel composite in aqueous solutions of metal salts. It is established that the kinetic constant of hydrogel collapse does not depend on the radius of metal ions at equal concentrations of the studied salts in a solution.