Acrylic acid-starch graft copolymers

Acrylic acid or methacrylic acid-starch graft copolymers were proposed as floc-culants for bauxites,2714,3095 agents for sizing cotton,3096-3098 tanning materials,3099 paper additives,3100 and also for sanitary napkins, diapers, tampons, and sick-bed sheets.3101-3104 Particular attention was devoted to the use of vinyl monomer grafted onto crosslinked starch.3105 Other applications include antiflammatory... 

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. 

The graft copolymers of acrylamide, acrylic acid, and cellulose or starch are used as water absorbents and in enhanced oil recovery systems. 

Superabsorbent polymers were developed in 1974. Initially, they were mostly graft copolymers of polysaccharides such as starch and cellulose. However, the majority of currently used superabsorbent pol3miers are lightly crosslinked acrylic acid polymers. 

The synthetic polyacrylates derived from acrylic acid, and the graft copolymers from starch and acrylic acid have emerged as the absorbent polymers of choice. This is in no small part due to economic factors, as a glance at any chemical marketing periodical will show acrylic acid as one of the least expensive water soluble monomers. In addition, the properties of acrylic acid make it relatively easy to polymerize, and to polymerize to products of high molecular weight. The importance of these latter properties will become clear in the next section. 

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