Preparation and Swelling Kinetic Analysis of Poly (HPMC-co-AA-co-AM) Super Absorbent Resin

Super absorbent resin (SAR) is prepared by aqueous high temperature polymerization using hydroxypropyl methylcellulose (HPMC) as monomer backbone material, acrylic acid (AA) and acrylamide (AM) as the graft copolymer monomer, potassium persulfate (KPS) as the initiator to generate free radicals, and N, N '-methylenebisacrylamide (MBA) as cross-linking agent for cross-linking reaction. Simutaneously, the influence of individual factors on the water absorption is investigated, and these factors are mainly AA, AM, KPS, MBA, HPMC, and reaction temperature. The optimized conditions are obtained by the experiment repeating for several times. The water absorption multiplicity and salt absorption multiplicity under the conditions are 782.4 and 132.5 g/g, respectivity. Furthermore, the effects of different temperatures and salt concentrations on its water absorption, as well as the swelling kinetics of SAR are studied. It is indicated the water-absorbing swelling process is mainly caused by the difference in water osmotic pressure and Na+ concentration inside and outside the cross-linked molecular structure of the resin, which is not only consistent with the quasi-secondary kinetic model, but also with the Fick diffusion model.