A series of biodegradable superabsorbent polymers (SAP) based on starch grafted with
acrylic acid (AA) and crosslinked with N,N’-methylenebisacrylamide (MBIS) were obtained. The
parameters that define SAPs properties, such as starch type, amount of initiator, acrylic acid and
crosslinker concentrations, and degree of neutralization were varied according to an experimental
design. The swelling rate, the degree of swelling, the water sorption isotherms and the texture
profile of the new materials were determined. A new method was used to measure the swelling rate.
The water sorption results were correlated using various isothermal models as the BET (Brunauer-
Emmett-Teller) and GAB (Guggenheim-Andersson-DeBoer) models.
Hydrogels obtained from regular cornstarch presented better absorption capacities than those
from waxy cornstarch. Maximum swelling was observed for 70% neutralization of carboxylic acid
groups. More rigid SAPs presented lower swelling rates, but not necessarily lower swelling degrees.
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