Effect of synthesis parameters and of temperature of swelling on water absorption by a superabsorbent polymer

Superabsorbent polymers are environmentally useful as water retention agents, for purposes such as agricultural applications and combating desertification. In this work, these polymers were synthesized to study the effects of synthesis parameters and of temperature of the swelling medium on water absorption. The polymers were synthesized by two polymerization techniques, free radical solution and free radical inverse emulsion ("S" and "E", respectively), and some pH values, 4 and 10 for S. and 7 for E. The monomers used were: acrylamide; 2-actylamido-2-methyl-propano-sulfonic acid; and N,N-methylene-bisacrylamide as a crosslinker. The temperature of the swelling medium was varied in the range 10 to 49 degrees C. The following effects were studied: effect of the polymerization technique and pH on the swelling capacity; and effect of temperature on the time to reach the equilibrium (final) swelling and its extent. The study confirmed expected results: polymers obtained by E at pH 7 reached a swelling almost as large as the polymers obtained by S at a higher pH of 10; and, regarding the swelling conditions, a higher temperature (above 38 degrees C), although significantly decreasing the equilibrium (final) swelling, led to a faster reaching of the equilibrium. (C) 2011 Elsevier B.V. All rights reserved.