Superabsorbent polymers absorption properties

A comprehensive overview of the properties of superabsorbent polymers, specific water absorption and desorption behavior of superabsorbent pol5uners in fresh and hardening concrete, the effects of the superabsorbent pol5uners addition on the rheological properties of fresh concrete, the changes of cement paste microstructure and mechanical properties of concrete have been reviewed (42). 

As already described, superabsorbency criteria depend on the absorbent s properties, the absorption measurement method and use method, and the conditions under which it is used with other materials. Therefore in this section we will not define superabsorbency as the maximum absorption of water with respect to the weight of the absorbent. Rather, it will be defined as optimum water absorption based on the purpose of the application. Employing this definition, we will discuss the synthesis of superabsorbent polymers, measurement of water absorption, absorbency and its water absorption characteristics, change of the required properties for superabsorbency in the main areas of, health applications, other superabsorbency of industrial materials, and moisture absorption of general superabsorbent polymers. 

The most important property of superabsorbent polymers is their ability to absorb water. Traditional water-absorbing materials such as cotton, pulp and sponges absorb water into interstices by capillary phenomenon. By contrast, superabsorbent polymer absorbs water into three-dimensional (3D) networks of a erosslinked polymer by the compatibility of polymer chains and water and by osmotic pressure. Hence, superabsorbent polymers laek absorption speed but have a much better water-absorption eapaeity eompared to cotton or pulp. Products that have a high water-absorption property include sanitary produets, such as disposable diapers, eonstmetion materials, mulch, water sealant for electric cables, freshness maintenance materials in the food industry. Of the sanitary products, of the disposable diaper is the best example of a product that has a high waterabsorbing capacity. The superabsorbent polymer is indispensable for disposable diapers, and it drastically improved the performance of disposable diapers. Here, the development and current status of disposable diapers, the structure of disposable diapers in which a superabsorbent polymer is incorporated, and advances in the development of superabsorbent polymers will be described. 

Because porous superabsorbent polymers possess large surface areas as well as chaimels and capillaries for liquid diffirsion, high blood-absorption rates can be expected. As shown in Fig. 4, the lower the bulk density (the property that relates to porosity) of superabsorbent polymers, the higher the blood-absorption rate. Thus, various porous superabsorbent polymers have been developed and their absorbencies are under investigation. 

A superabsorbent polymer was used as a thickener for sodium sulfate decahydrate [11], There is also a report that a superabsorbent polymer having a water absorptivity of 600 times its volume was added at a 2.9 wt% amount. When sodium sulfate deeahydrate repeated the melting-solidification cycle 100 times, there was no separation of water [12]. Even very small amounts of superabsorbent polymer ean enhanee viscosity and more than 90% of the water held is free water. Henee, use of this type of polymer as a thickener effeetively takes advantage of water retention, water supply, dispersion stabilization, and the viseosity enhancement properties of superabsorbent polymers [13]. 

James HM, Guth E (1943) Theory of the elastic properties of rubber. J Chem Phys 11(10) 455-481 Kabiri K, Omidian H, Hashemi SA, Zohuriaan-Mehr Ml (2003) Synthesis of fast-swelling superabsorbent hydrogels effect of crosslinker type and concentration on porosity and absorption rate. Eur Polym J 39(7) 1341-1348... 

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