Effects of Structural Variables on AUL and Rheological Behavior of SAP Gels

The swelling properties of superabsorbent polymers (SAPs) under real conditions are extremely important for selecting the material suitable for a given application, e.g. feminine napkin or agriculture. This new practical research represents deeper synthetic and physicochemical studies on the structure-property relation in acrylic SAP hydrogels and composites. Thus, the values of saline-absorbency under load (AUL; a measurable simulation of the real circumstances of SAP applications, at pressures 0.3-0.9 psi) were measured for the SAP or SAP composite samples prepared under different conditions, i.e. type and content of crosslinker, type and concentration of initiator, percentage of inorganic filler (kaolin), and type and percentage of porosity generators. The samples were subsequently used to determine the rheological and morphological characteristics. Dynamic storage modulus (G') measurements were carried out at constant strain in a wide range of frequency. Linear correlations were frequently found to be active between AUL and G' data over the rubber-elastic plateau. Thus, for a given SAP: AUL=k(total)G' + C. The coefficient k total is a function of (nature and content of crosslinker, initiator, inorganic component, particle morphology, etc.). Therefore, the easily measured AUL values could be simply correlated to the main synthesis variables and molecular structure of SAP gels through a rheological material function (G'). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 3676-3686, 2009