Concise synthesis of fast-swelling superabsorbent hydrogels: Effect of initiator concentration on porosity and absorption rate

Fast-swelling superabsorbent hydrogels were prepared through a highly concise solution polymerization process. The ammonium persulfate/sodium metabisulfite redox pair initiating system was used to polymerize partially neutralized acrylic acid and N,N'-methylenebisacrylamide as crosslinker. The reactions were performed under atmospheric conditions in the presence of blowing agents to obtain highly porous superabsorbent networks in the form of white foams. Effect of the initiator concentration on reaction kinetic parameters, i.e. gelation time and temperature, maximum temperature of the reaction, and the product density were studied. Swelling behavior of the porous superabsorbents, in both distilled water and saline solutions was also investigated in terms of different initiator concentrations. The swelling kinetics was mainly studied by means of a Voigt-based viscoelastic model. Water-swelling capacity and rate parameter of the superabsorbents were measured to be 112-736 g/g and 14-109 seconds, respectively.