Applications of superabsorbent polymers in medicine and healthcare

Since their introduction into the consumer market in the 1980s, SAPs have found widespread uses in personal disposable hygiene products, such as baby diapers, adult protective underwear, and sanitary napkins. In addition, these materials are used in a number of novel biomedical products such as surgical caps and drapes, as well as niche products like contact lenses and wound dressings, utilizing their ability to hold a large amount of water in the swollen polymeric structure. 

The high absorption capacities of SAPs are particularly suited to absorbent products in personal healthcare and hygiene. These products all contain an absorbent core, which may be made up of natural or synthetic fibers, SAPs, or a mixture of fluff and SAPs. A top layer is used to carry fluid into the absorbent core while maintaining dryness against the skin. This so-called topsheet, which is made of synthetic or natural fibers, and a backsheet, which is usually a polyethylene film or a fllm/nonwoven composite, are combined with the absorbent core to form a final product that may be used in a number of healthcare and hygienic applications. 

A diaper (in American and Canadian English) or nappy (in Conunonwealth English) is a kind of underwear that allows one to defecate or urinate in a discreet manner. Diapers have been worn throughout human history, and are made of cloth or disposable materials. Cloth diapers are composed of layers of fabric made from cotton, hemp, bamboo, or microflbers, and can be washed and reused multiple times. Disposable diapers contain absorbent materials and are thrown away after use. The decision to use cloth or disposable diapers is a controversial one, due to issues ranging from convenience, health, and cost due to their effect on the enviromnent. 

During the production process, SAPs in grannlar or powder forms are added to baby diapers in two ways layered or blended. In the layered method, powdered SAPs are first scattered on a layer of flnff pulp before it is folded, so the SAPs are located in a centralized layer in the absorbent structure, which is further covered with a nonwoven fabric layer. In the blended application, the SAPs are first mixed homogeneously with the fluff pulp before the mixture is laid down to form the absorbent structure, which is subsequently covered with a nonwoven fabric. 

Dnring the development of diapers with improved performance, a separate layer of nonwoven fibers was added to improve urine distribution in the diaper. This distribution layer is placed between the composite absorbent core, consisting of cellulose fiber and SAPs, and the porous cover sheet. The distribution layer has a lower absorbency than either the standard cellulose fluff or SAP, thus allowing fast liquid distribution within the diaper. This layer is often made from nonabsorbent nonwoven materials such as polypropylene fibers, with snfficient porosity to allow liquid to pass through freely. 

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