Superabsorbent hydrogel composites

new cost-effective approach to enhance gel strength of superabsorbent hydrogels was invented. Superabsorbent hydrogel composites (SHCs) were prepared through an optimized rapid solution polymerization of concentrated Partially neutralized acrylic acid in the presence of a crosslinking agent under normal atmospheric conditions. Kaolin was used as an inorganic component in the polymerization process to strengthen the hydrogel products. FT-IR spectroscopy was used to confirm grafting of acrylic chains on to the surface of kaolin particles. Morphology of the products was studied by scanning electron microscopy (SEM). Compared with the kaolin-free hydrogel (control), kaolin caused a reduced equilibrium swelling and swelling rate as low as 17-31% and 19-29%, respectively. Kaolin, however, resulted in enhanced gel strength as high as 21-35% compared to the control. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study thermal properties of the composites. The SHCs exhibited higher thermal stability than the control. Meanwhile, changes in certain thermal transitions reconfirmed the chemical interaction of the acrylic chain with kaolin. These thermostabilized strengthened superabsorbent hydrogels may be considered as good candidates for agricultural application to retain more water under soil pressure. Copyright (C) 2003 John Wiley Sons, Ltd.