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Synthesis and characterization of superabsorbent hydrogels based on hydroxyethylcellulose and acrylic acid
Tamás Fekete1, Judit Borsa2, Erzsébet Takács3
1Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, H-1525 Budapest 114, P.O. Box 49, Hungary; Faculty of Chemical Technology and Biotechnology, Budapest University of Technology and Economics, H-1521 Budapest, P.O. Box 91, Hungary.
Abstract:
Hydroxyethylcellulose (HEC)/acrylic acid (AAc) copolymer gels with superabsorbent properties were synthesized from aqueous solutions by radiation-initiated crosslinking. The effect of the acrylic acid content on gel properties was determined at different synthesis conditions. The partial replacement of the cellulose derivative with acrylic acid improved the gelation, leading to higher gel fraction and lower water uptake even in very low concentrations (1-5%). In the presence of acrylic acid lower dose and solute concentration was required for the gel synthesis. The molecular properties of the hydroxyethylcellulose also had a major effect on the gelation: higher molecular mass resulted in better gel properties. The acrylic acid also affected the electrolyte sensitivity of the hydrogels: while pure HEC gels were unaffected by the ionic strength of the solvent, the water uptake of HEC/AAc gels decreased with the salt concentration. The sensitivity also depended on the acrylic acid ratio.