Polymers are substances whose molecules have high molar masses and are composed of a large number of repeating units. Polymers are formed by chemical reactions in which a large number of molecules called monomers are joined sequentially, forming a chain. Super absorbent polymers (SAP) and Hydrogels are very unique water-absorbing and water-holding materials. They are solid, granular or powder cross linked polymers that rapidly absorb and retain large volumes of aqueous solutions. It can absorb up to 500 times of its own weight of pure water and even under pressure resist release of the absorbed water(1). The absorptive properties of SAP are ideally suited for the absorption and solidification of various types of liquids like water, sludge and blood.
These are growing in use in the medical industry as coverings for wounds; In the plant industry as a way to deliver water to plants slowly over an extended period of time; With forest fire fighting groups as a protective covering for houses at risk; In the space program as giant diapers for astronauts during takeoff and space walks, and; In the disposable baby and adult diaper industry. In each of the uses, the important characteristic of hydrogels is its ability to serve as a super absorber and to keep the surrounding area damp but not wet. This is done by forming a gel with the polymer as the solid net surrounding the suspended liquid, water.
Gels are formed by one of the class of matter (liquid, gas or solid) enclosing and suspending a different class. Solids in gas, gas in solids, liquid in gases, solids in liquids or in this case liquids suspended in a solid. The hydrogels containing amide, amine, carboxylic acid, and ammonium groups, can bind heavy metal ions and dyes through the polar functional groups, and be used as good absorbents for water purifications(2,3). The absorption rate of the polymers differs according to their mechanism used for preparation.
Nurseries : A major application for super absorbents in the nursery industry is to improve the moisture holding capacity of soil and soil-less mixes. In addition, using super absorbents can increase aeration and drainage. Increased aeration reduces the likelihood of root rot since there is a better opportunity for root gas exchange. The increase in aeration and expansion of the growing media occurs as superabsorbent particles expand. In expanding they push surrounding soil particles apart, loosening the media, increasing pore space.