The present invention relates to a process for producing postcrosslinked water-absorbing polymeric formations, comprising the steps of contacting water-absorbing polymeric formations P1 obtained by polymerization of ethylenically unsaturated acid-functional monomers or salts thereof in the presence of a crosslinker with a fluid F1 comprising a postcrosslinker, heating the water-absorbing polymeric formations in contact with the fluid F1 to a temperature in a range from 40 to 300° C. to obtain postcrosslinked water-absorbing polymeric formations P2, the water-absorbing polymeric formations P1 having a thermal stability, as determined in accordance with the test method described herein, of less than 3.0%. The invention also relates to water-absorbing polymeric formations, to the water-absorbing polymeric formations obtainable by this process, to water-absorbing polymeric formations based on crosslinked carboxyl-bearing monomers, to a composite comprising water-absorbing polymeric formations and a substrate, to a process for producing a composite, to a composite obtainable by this process, to chemical products comprising water-absorbing polymeric formations or a composite, to the use of water-absorbing polymeric formations or of a composite in chemical products and also to the use of triallyl isocyanurate as an internal crosslinker in the production of water-absorbing polymeric formations based on crosslinked carboxyl-bearing monomers.