Studies on poly(acrylic acid)/attapulgite superabsorbent composites. II. Swelling behaviors of superabsorbent composites in saline solutions and hydrophilic solvent–water mixtures

Abstract

ABSTRACT:The effect of the attapulgite content on the swelling for a series of poly(acrylic acid)/attapulgite superabsorbent composites in water was studied. The effects of the temperature and pH values on the water absorbency of the superabsorbent composites were investigated. The swelling behavior of the superabsorbent composites in various saline solutions was also investigated. The water absorbency in various salt solutions decreased with an increase in the ionic strength of the solutions. At a high ionic strength (Ͼ1 ϫ 10 Ϫ3 M), the water absorbency in monovalent cationic solutions was higher than that in multivalent cation solutions. This dramatic reduction of the water absorbency in multivalent cationic solutions of high ionic strength may have been due to the complexing ability of the carboxylate groups inducing the formation of intramolecular and intermolecular complexes, which resulted in an increased crosslink density of the network. The swelling behavior of the superabsorbent composites in mixtures of water and hydrophilic solvents, including methanol, acetone, ethanol, and dimethyl sulfoxide (DMSO), was also investigated. The water absorbency decreased with an increase in the concentration of any of the four organic solvents, and two transitions were observed in the superabsorbent composite/hydrophilic solvent-water mixture systems. The main transition for the four hydrophilic solvent-water mixtures was a collapse of the swollen gel (at 50 -80% methanol, 30 -80% acetone, 50 -80% ethanol, and 50 -80% DMSO). For the methanol-water system, the magnitudes of the first and second transitions for the poly(acrylic acid)/attapulgite superabsorbent composites containing lower proportions of attapulgite were larger than those for the superabsorbent composites with higher attapulgite contents. The effect of the mixture temperature on the water absorbency of the superabsorbent composites in 10 min was also reported.

Superabsorbent Polymer Properties and Concentration Effects on Water Retention under Drying Conditions

“…Various clay minerals, and especially attapulgite, are incorporated in SAPs to reduce production cost, and also to improve the properties (e.g., swelling ability, gel strength, mechanical and thermal stability) of the SAPs (Li et al, 2004Zhang et al, 2007). Moreover, it has been reported that, compared with other clay minerals, such as kaolinite or vermiculite, attapulgite-based superabsorbent composite is more effective in absorbing high levels of water in systems containing univalent cations (Li et al, 2004Zhang et al, 2007). Prior to using the SAPs, the samples were dried in an oven at 60°C for 3 h to obtain ~ 95% active ingredients and only ~5% water.…”

Swelling behavior of polyacrylamide/laponite clay nanocomposite hydrogels: pH-sensitive property

“…Haraguchi et al considered that a unique organic/inorganic network structure was formed by in situ free-radical polymerization, in which the PNIPA chains were attached to the surface of clay sheets, which acted as effective multifunctional cross-linkers through ionic or polar interactions. Furthermore, Li et al have recently reported the swelling behaviors of clay based super-absorbent composites [16].…”

Swelling Behavior of Guar Gum-g-Poly(Sodium Acrylate -co-Styrene)/Attapulgite Superabsorbent Composites

“…[13] It is well known that the swelling properties of hydrogels are dependent on the structure of its 3D polymeric network and the swelling media. [15,16] Li et al [17] synthesized a type of poly(acrylic acid)/attapulgite (PAA/APT) superabsorbent composite and investigated its swelling behaviors in saline solutions and hydrophilic solvent/water mixtures. It has been reported that the incorporation of the proper amount of APT could enhance the absorbing ability of PAA hydrogel.…”