Synthesis and modification of salt-resistant superabsorbent polymers

A salt-resistant superabsorbent, poly(acrylamide-co-acrylic acid) was synthesized from solution polymerization. To improve the properties of swollen hydrogel such as strength, resilience and dispersion, the copolymer was surface-crosslinked with ethylene glycol diglycidyl ether, and then the surface-cross I inked copolymer was blended with aluminum sulphate (Al-2(SO4)(3)) together with sodium carbonate (Na2CO3) to obtain the aim sample. The factors that influenced the aim sample's properties were investigated, and the optimum conditions were obtained as follows: the molar ratios of sodium hydroxide (NaOH) to acrylic acid, acrylamide to acrylic acid, initiator [denoted with hydrogen peroxide (H2O2)] to acrylic acid, and ethylene glycol diglycidyl ether to acrylic acid were 65-70%, 30%, (7-11) x 10(-5), and (2.5-3.5) x 10(-4), respectively, the mass ratio of Al-2(SO4)3 to crosslinked copolymer was 4.25% and the reaction time was 0.5-2 h. The water absorbency of the sample prepared at the above conditions in 0.9 wt% NaCl aqueous solution under certain load (P approximate to 2 x 10(3) Pa) and at atmosphere pressure were 17 and 60 g g(-1), respectively. Moreover, excellent strength, resilience and dispersion could be shown by this sample. (C) 2004 Elsevier B.V. All rights reserved.