Effect of number of grindings of attapulgite on enhanced swelling properties of the superabsorbent nanocomposites

The incorporation of clay has become a preferred method for superabsorbent composite preparation because of its great influence on the swelling properties. The mechanical chemistry shows that grinding treatment could change the physical and chemical properties of clay. Therefore, in this article, the grinding treated attapulgite were used for preparation of sodium carboxymethyl cellulose- g-poly(acrylic acid)/attapulgite superabsorbent nanocomposites by the solution polymerization using ammonium persulfate as an initiator and N,N′-methylenebisacrylamide as a crosslinker. The effects of number of grindings on the specific surface area and other characteristics of attapulgite, and the swelling ability, swelling kinetics, saline and pH sensitivity of the superabsorbent nanocomposites were systematically investigated. The results indicated that the increase in number of grindings could decrease the length of single crystals and dissociate part of crystal aggregates of attapulgite, which affected the dispersion of attapulgite in the polymeric matrix, thus leading to change in swelling behaviors of the superabsorbent nanocomposites. The swelling tests showed that the superabsorbent nanocomposites with attapulgite grinded for 6 times were the best in the reswelling abilities, initial swelling rate, saline and pH sensitivity.