PREPARATION OF SUPERABSORBENT POLYMERS BY CROSS-LINKING ACRYLIC-ACID AND ACRYLAMIDE COPOLYMERS

High water-absorbent copolymers comprising acrylic acid (AA) and acryl amide (AM) were prepared in the presence of a crosslinking agent, mono functional aldehyde, by a solution polymerization technique using a re dox initiation system. Such copolymers have very high water absorbency and absorbing kinetics to the distilled water. The copolymer formed w hich absorbed about 900 g water/g dry copolymer was used to study the influence of sodium chloride on the absorption capacity at 24 degrees C. The swelling of this copolymer was studied in alcohol/water mixture s of increasing alcohol content at 294, 304, and 314 K. The main trans ition for ethanol/water and methanol/ water mixtures is a rapid decrea se of the retention capacity of the copolymer at 50-60 vol % ethanol a nd 55-65 vol % methanol, respectively. Swelling in distilled water at different temperatures (T) and the effect of solvent composition were also studied. Among the variables examined were initiator concentratio n, polymerization temperature, and amount of AM in the copolymer. (C) 1997 John Wiley & Sons, Inc.