Synthesis and swelling behaviour of fast-swelling superabsorbent composites

Abstract

Fast-swelling porous superabsorbent composites with high water absorbency in 0.9 wt% NaCI solution both at atmospheric pressure and under certain load (p ≈2x103 pa) were synthesized by a rapid solution polymerization of concentrated sodium acrylate, acrylamide and 2-hydroxypropyl acrylate. The porosity was induced through foaming conducted in the course of polymerization using acetone as porosity generator. The copolymerizatlon and surface morphology of the porous copolymers were characterized by FTIR and SEM. To improve other properties of swollen hydrogel such as strength, resilience and dispersion, the copolymers were modified with inorganic salts after surfacecrosslinking by trihydroxymethyl propane glycidol ether. The influences of various experimental conditions, such as neutralization degree of acrylic acid, amount of initiator and crosslinker on the water absorbent capacity in 0.9 wt% NaCI solution were investigated. The resulting products under optimum conditions possessed the water absorbency of 65 gg-1 and 10 gg-1 in 0.9 wt% NaCI solution at atmosphere pressure and under load, respectively. The results of swelling kinetics measurement in 0.9 wt% NaCI solution showed that the composites had very fast swelling rate (they can reach swelling equilibrium in minutes). In addition, the effect of amount of acetone on swelling rate of the composites was examined in detail. It was shown that appropriate amount of acetone caused products with high porosity, which led to large swelling rate. Moreover, the swollen hydrogel exhibited excellent strength, better resilience and dispersion.