Theoretical and experimental investigation of the swelling behavior of sodium polyacrylate superabsorbent particles

Sodium polyacrylate superabsorbent polymers were prepared in particle forms by the inverse suspension technique. The surfactant concentration effect on the polymer particle size was analyzed with molecular sieves and an optical microscope. Water absorption and desorption characteristics were analyzed by the gravimetric method. The equilibrium water uptake in sodium polyacrylate particles was strongly dependent on both the salt concentration of the aqueous media and the crosslinking density of the polymers. The polymer crosslinking density was determined from the measurement of Young's modulus and the polymer-solvent interaction parameter from the equilibrium swelling experiment. The degree of inonization was predicted from experimental measurements, and theoretical analysis was performed on the effects of the salt concentration and polymer crosslinking density on the equilibrium water swelling ratio.