Preparation of composites and nanocomposites based on bentonite and poly(sodium acrylate). Effect of amount of bentonite on the swelling behaviour

A series of composite and nanocomposite hydrogels were synthesized by copolymerization reaction of partially neutralized acrylic acid (SA) on bentonite micropowder (BT) using N,N'-methylenebisacrylamide (MBA) as a crosslinker and potassium persulfate (1) as an initiator in aqueous solution. The influences of Na+-BT, organoBT (O-BT), and the content of the BT in the copolymeric gels on the swelling behaviour in deionized water and saline solution (0.2 wt.% NaCl(aq)) were investigated. Results showed that the equilibrium swelling (W.) was decreased by adding a small amount of the BT, however, at higher BT contents, the W. increased with the increase of the amount of clay. It was found that a concentration of 14 wt.% Na+-BT gave the best results absorption (955 g/g). Moreover, the amount of swelling for these absorbents in saline solution was smaller than that in deionized water. These hydrogels were characterized by X-ray diffraction and scanning electron microscopy. Finally, the thermogravimetric analysis indicated that introduction of clay to the polymer network resulted in an increase in thermal stability. (c) 2006 Elsevier Ltd. All rights reserved.