Synthesis of superabsorbent polymers

A variety of monomers, mostly acrylics, is used to synthesize SAPs. Acrylic acid, and its sodium or potassium salts, and acrylamide are most often used in the industrial production of SAPs. The AA monomer is inhibited by methoxyhydroquinone to prevent spontaneous polymerization during storage. A number of other monomers such as methacrylic acid, methacrylamide, acrylonitrile, 2-hydroxyethylmethacrylate (HEMA), A-vinyl pyrrolidone, vinyl sulphonic acid, and vinyl acetate, and biopolymers such as cellulose, starch, chitosan, gelatin, and some of their derivatives are also used as raw materials for the production of SAPs. 

Several parameters are important for the production of high-quality SAPs. First, a good balance must be maintained between the molecular weight of the polymer and the yield of the production process. Low-molecular-weight species are extractable, whereas high-molecular-weight species require a longer polymerization time. Commercial SAPs typically contain 5-20% extractables. 

In summary, the following reaction variables affect the properties of acrylic anionic SAPs. 

and amount of inorganic particles incorporated. 

Porosity generating method or the amount and type of the porogen. 

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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. 

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