Polymers superabsorbent

Superabsorbents. Water-sweUable polymers are used extensively in consumer articles and for industrial appUcations. Most of these polymers are cross-linked acryUc copolymers of metal salts of acryUc acid and acrylamide or other monomers such as 2-acrylamido-2-methylpropanesulfonic acid. These hydrogel forming systems can have high gel strength as measured by the shear modulus (134). Sometimes inorganic water-insoluble powder is blended with the polymer to increase gel strength (135). Patents describe processes for making cross-linked polyurethane foams which contain superabsorbent polymers (136,137). 

B Kabra, SH Gehrke. Rate limiting steps for solvent sorption and desorption by microporous stimuli-sensitive absorbent gels. In FL Buchholz, NA Peppas, eds. Superabsorbent Polymers Science and Technology. ACS Symp Ser 573. Washington, DC American Chemical Society, 1994, pp 76-87. 

Another variation on the luminol CL sensor for N02 was introduced by Collins and Ross-Pehrsson [12] where a solid-phase reagent was positioned below a PMT, across which the air under test is pumped. Of the hydrogel or polymeric sorbents investigated, a Waterlock superabsorbing polymer (hydrogel)... 

Hydrogels, 13 729-759. See also Microgels Superabsorbent polymers (SAPs) AMPS polymer, 23 721 applications for, 13 747-753 biodegradable, 13 739-742 bioerodible, 9 63 conducting, 7 524 cross-linked poly (ethylene oxide),... 

Super abrasive grinding wheels, 1 21 Superabsorbent polymers (SAPs),... 

Note 2 The swelling ratio of a superabsorbent polymer can reach the order of 1000 1. Note 3 Superabsorbent polymers for water are frequently poly electrolytes. 

Acrylic acid and its salts are raw materials for an important range of esters, including methyl, ethyl, butyl, and 2-ethylhexyl acrylates. The acid and its esters are used in polyacrylic acid and salts (32%, including superabsorbent polymers, detergents, water treatment chemicals, and dispersants), surface coatings (18%), adhesives and sealants (15%), textiles and non-wovens (12%), plastic modifiers (5%), and paper coating (3%). 

Superabsorbent polymers were first described in 1938, when polymer chemistry was still a fledgling field. Chemists had discovered that small molecules could be linked together to... 

Masuda F (1987) Superabsorbent Polymers (in Japanese) Kyoritsu, Tokyo... 

The class of hydrophilic and water-absorbent polymers are superabsorbent polymers (SAP). Super absorbent polymers are polymers that can absorb and retain extremely large amounts of a liquid relative to its own mass. 

Superabsorbent polymers are now commonly made from the polymerization of acrylic acid blended with sodium hydroxide in the presence of an initiator to form a polyacrylic acid, sodium salt (sometimes referred to as cross-linked sodium polyacrylate). Some of the polymers include polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxy-methyl-cellulose, polyvinyl alcohol copolymers, cross-linked polyethylene oxide, and starch grafted copolymer of polyacrylonitrile to name a few. The latter is one of the oldest SAP forms created. 

Today, superabsorbent polymers are made using one of two primary methods suspension polymerization or solution polymerizations. Both processes have their advantages over the other and both yield a consistent quality of product. 

Fig. Z22 View of superabsorbent polymer network with cross-linked sites (SAP)...

The polyacrylate (known as a superabsorbent polymer or SAP by the diaper industry) is distributed throughout the fluff pulp. Another name for these crystals is Waterlock . It is also used for plants to help retain water in the soil. The polyacrylate under pressure can hold an amount of liquid that is as much as thirty times its weight. This correlates to the compression (pressure) that occurs when a baby would sit or lie on the diaper. The polyacrylate allowed the manufacturers to reduce both the weight and thickness of the diaper by 50 percent and increase its absorbency. 

Buchholz, Fredric L., and Peppas, Nicholas A., eds. (1994). Superabsorbent Polymers, Science and Technology. Washington, DC American Chemical Society. 

Another important bulk chemical that could be derived from glycerol is acrylic acid (Craciun et al., 2005 Shima and Takahashi, 2006 Dubois et al., 2006). Shima and Takahashi (2006) reported a complete process for acrylic acid production involving the steps of glycerol dehydration in a gas phase followed by the application of a gas phase oxidation reaction to a gaseous reaction product formed by the dehydration reaction. Dehydration of glycerol could lead to commercially viable production of acrolein, which is an important and versatile intermediate for the production of acrylic acid esters, superabsorber polymers or detergents (Ott et al., 2006). Sub- and supercritical water have been applied by Ott et al. (2006) as the reaction media for glycerol dehydration, but the conversion and acrolein selectivities that have been achieved so far are not satisfactory for an economical process. 

Smith [2] prepared a series of superabsorbent polymers with high permeability consisting of the reaction product of NaOH, water, acrylic acid, methoxypo-lyethyleneglycol (750), monomethacrylate of trimethylolpropanetriacrylate, TMP-3EO, and hydroxymonoallyl ether-lOEO. These materials were useful in the transportation of liquids in the swollen state. 

Meth)acrylic acid and esters are large-volume industrial chemical intermediates for the production of co- and homopolymers. Acrylic acid (AA), with a worldwide production of approx. 1.5 X 10 t/a, finds its main use in the manufacture of superabsorbent polymers and various acrylate esters. The most important production process for AA involves the two-stage oxidation of propene (via acrolein) in the presence of a large excess of steam by heterogeneous catalysts. Selectivities to AA for the overall process reach 85-90% based on propene (cf. Chapter 1, Introduction). 

Woven cloth, cotton wadding, cellulose fiber batt, papers, and foamed polyurethane have been used as traditional absorbent materials for water. These materials can absorb 1-20 g of water per gram material and the water absorbed is easily removed from the materials by applying low pressure. In recent years, superabsorbent polymers, which can absorb up to 1000 g of water per gram of polymer and up to about 100 g of dilute salt solution per gram of polymer and the water absorbed can hardly be removed from the polymers even by applying high pressure, have been prepared and commercially used in many applications. 

Superabsorbents are superabsorbent polymers, which are loosely crosslinked hydrophilic polymers and have ionic charges in the polymers. They absorb water, swell, and retain aqueous solution above hundred times their own weight. Because of the excellent characteristics, the superabsorbents have been widely used in many applications such as disposable diapers, feminine napkins, soil additives in agricultural or horticultural applications, gel actuators, water-blocking tapes, materials for drug delivery system, absorbent pads, etc., where water absorbency or water retention is important. 

On the other hand, superabsorbent polymers having anionic groups that were made from low crosslinked starch or synthetic polymers were found to have high... 

Superabsorbent polymers should be essentially hydrophilic polymers. Therefore, natural polymers such as starch and cellulose or synthetic polymers such as poly(acrylate), poly(vinyl alcohol), poly(acrylamide), or poly(oxyethylene) are used as hydrophilic base polymers. 

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