Study on superabsorbent composite. VI. Preparation, characterization and swelling behaviors of starch phosphate-graft-acrylamide/attapulgite superabsorbent composite

A novel starch phosphate-graft-acrylamide/attapulgite superabsorbent composite was prepared by graft-copolymerization among starch phosphate, acrylamide, and attapulgite in aqueous solution. In this paper, factors influencing water absorbency of the superabsorbent composite such as the molar ratio of NaOH to AM and the amount of starch phosphate and attapulgite were investigated. The superabsorbent composite acquired the highest equilibrium water absorbency of 1268 g g(-1) when the molar ratio of COO-, COOH and CONH2 is 10:3: 11, the weight ratio of AM to starch phosphate is 5: 1, and 10 wt% attapulgite was incorporated. The graft-copolymerization reaction mechanism, morphology, and thermal stability of the composites were also investigated by FTIR, scanning electron microscopy, and thermo-gravimetric analysis, respectively. The introduced starch phosphate and attapulgite endowed the composite a higher thermal stability. In addition, swelling rate, and equilibrium water absorbency in various saline solutions were investigated to study the effect of starch phosphate and attapulgite on swelling behaviors of the composite. The results indicate that the phosphorylation of starch and the introduction of attapulgite could greatly improve equilibrium water absorbency, swelling rate and salt-resistant properties of corresponding superabsorbent composite. (c) 2006 Elsevier Ltd. All rights reserved.