Preparation and swelling behavior of fast-swelling superabsorbent hydrogels based on starch-g-poly (acrylic acid-co-sodium acrylate)

A novel fast-swelling porous superabsorbent hydrogel was prepared by grafting acrylic acid onto corn starch through free-radical polymerization in aqueous solution using N,N'-methylenebisacrylamide as a crosslinker, ammonium persulfate as an initiator, sodium dodecyl sulfate and p-octyl poly(ethylene glycol)phenyl ether as pore-forming agents. The graft polymerization and surface morphology of the porous superabsorbents were characterized by FTIR and SEM. The results indicate that the porous superabsorbents were endowed with higher equilibrium water absorbency and faster swelling rate (they needed only 10 min to reach 90% of their equilibrium water absorbency) compared with the nonporous superabsorbents. The dewatering method employed had a significant influence on the swelling behavior of the superabsorbents and dewatering agents were useful to preserve the pores formed during the polymerization process.