Relationship between water absorbency and reaction conditions in aqueous solution polymerization of polyacrylate superabsorbents

Polyacrylate superabsorbents were prepared by in situ aqueous solution poly merization in a polyethylene bag, which was submerged in a water bath. The influence of the initiator content, bath temperature, isopropanol content, initial monomer concentration, and crosslinker content (Cc) on water absorb ency (Q) were investigated. The temperature change of the monomer mixture d uring polymerization was also analyzed. Increase of the chain ends in netwo rks resulting from decrease of the molecular weight in free-radical polymer ization causes an increase of the water absorbency of superabsorbents and a lso reduces the crosslinking efficiency. The results are in conformity with the classical network theory. An empirical relation of Q = 2.45 Cc(-0.600) was obtained and the validity of Flory's swelling equation was confirmed i ndirectly. (C) 2000 John Wiley & Sons, Inc.