REVIEW Advances in non-hygienic applications of superabsorbent hydrogel materials M. J. Zohuriaan-Mehr • H. Omidian • S. Doroudiani • K. Kabiri Received: 26 May 2010 / Accepted: 19 July 2010 / Published online: 4 August 2010 Ó Springer Science+Business Media, LLC 2010 Abstract Superabsorbent polymers (SAPs) are organic materials with lightly crosslinked three-dimensional struc- ture possessing high to very high swelling capacity in aqueous media. These are in fact the most commercially successful members of the hydrogel family. The SAP production for personal care products (baby diapers and feminine incontinence products) accounts for about 80% of the overall hydrogel production. Research during the past 30 years, although not affected the commercial status of SAPs, has led to more and more understanding of super- absorbent structures, their properties, and potential uses. Beyond the hygienic use, the SAPs have found very wide applications from the agricultural formulations to phar- maceutical dosage forms. Since hygiene applications of SAPs are very well established and well reviewed, this article reviews and highlights the SAP applications in other sectors, such as in agriculture, pharmaceutics, separation technology, fibers/textiles, water-swelling rubbers, soft actuators/valves, electrical and construction. Introduction Hydrogels are macromolecular networks of hydrophilic polymer chains, with the ability to absorb aqueous fluids. In contact with the aqueous medium, the hydrogels swell to the extent, which is mainly determined by the hydrogel network crosslink density. Hydrogels, in general, are highly crosslinked and are made of less hydrophilic monomers, such that their absorption capacity is very low. Superabsorbent polymer (SAP) hydrogels, on the other hand, are generally based on ionic monomers and are lightly crosslinked; therefore, they display an exceptional capacity of water absorption [1]. While swelling or absorption capacity of general hydrogels in water is less than 100% (1 g/g), the SAPs can imbibe as much water as about 1,000–100,000% (10–1,000 g/g) [2]. With the initial and successful use of hydrogels in contact lenses, the hydrogel applications are now wide- spread [3–6]. Hydrogels are currently used as scaffolds in tissue engineering, where they may contain cells to repair defective tissues. Environmentally sensitive hydrogels can sense the changes in pH, temperature, or the concentration of metabolite, so that they can release their load as a result of such changes. Hydrogels that are responsive to specific molecules (e.g., glucose or antigens) can be used as bio- sensors and as controlled-release delivery systems for bio- active agents and agrochemicals. The SAP hydrogels with the ability to absorb urine and blood are used in hygiene products such as in baby diapers and feminine incontinence products, and they account for most of the commercial SAP use. Since there are several review papers on hygienic use of the SAP hydrogels, this article attempts to cover non-hygienic applications of SAPs. M. J. Zohuriaan-Mehr (&) Á K. Kabiri Iran Polymer and Petrochemical Institute (IPPI), P.O. Box 14965-115, Tehran, Iran e-mail: m.zohuriaan@ippi.ac.ir; mjzohuriaan@yahoo.com H. Omidian Nova Southeastern University, College of Pharmacy, 3200 South University Drive, Ft. Lauderdale, FL 33328, USA S. Doroudiani 2 Keele Street, Toronto, ON M6P 4C1, Canada 123 J Mater Sci (2010) 45:5711–5735 DOI 10.1007/s10853-010-4780-1