Thermo-hydrolytic stability of swelling capacity of superabsorbing composite hydrogels based on AMPS and acrylamide

N,N'-Methylenebisacrylamide (MBA) is a conventional crosslinker most often used to produce hydrogels. We have previously shown that MBA-crosslinks were thermo-hydrolytically cleaved upon heating during oven-drying, particularly in hydrogels based on 2-acrylamido-2-methylpropane sulfonic acid (AMPS). The present paper deals with the effect of comonomer acrylamide (AM, ranged 0-100%) and an organomodified clay on swelling stability of MBA-crosslinked poly(AMPS-AM) superabsorbing composite hydrogels. It was found that either AM or the organoclay had constructive effects on thermo-hydrolytic stability of the network through delaying or stopping the undesirable swelling changes originated from the crosslink cleavage, de-crosslinking. The incorporated organomodified clay, however, exhibited fewer stabilizing effect rather than AM, when AM content was higher than 15%. The swelling of hydrogels was turned out to be stable during heating even at high temperature (200 A degrees C) when they composed at least 15% AM. Based on rheometrical studies, swollen gel strength of heated composite hydrogel was typically shown to be significantly higher than that of the clay-free counterpart.