Development history and synthesis of super-absorbent polymers: a review

Super-absorbent polymers (SAPs) refer to a three-dimensional network polymer, water-swellable, water-insoluble, organic or inorganic material that can absorb thousands of times its own weight of distilled water. It is widely used in various fields, such as: agricultural, biomedical, daily physiological products, separation technology and wastewater treatment. In the review, the development history of superabsorbent polymers since 1961 is described, and the polymerization methods of superabsorbent polymers and the wide-ranging use of this type of polymers in life are described in detail. The article introduces four basic polymerization methods, bulk polymerization, solution polymerization, suspension polymerization and radiation polymerization from the preparation methods and types. Not only the detailed methods of polymerization but also their respective advantages and disadvantages are introduced. In recent years, new progress has been made in polymerization methods, for example, in-situ polymerization to obtain an onion-like multilayer tube cellulose hydrogel. The hydrogel has super-absorbent properties, and the water swelling mechanism is briefly introduced. Finally, the latest advances in super-absorbent polymers are pointed out.