Water gel beeds

Water crystals

Superabsorbent polymers (SAP) (also called slush powder) are polymers that can absorb and retain extremely large amounts of a liquid relative to their own mass.

Water absorbing polymers, classified as hydrogels,absorb aqueous solutions through hydrogen bonding with the water molecule. So an SAP's ability to absorb water is a factor of the ionic concentration of an aqueous solution. In deionized and distilled water, SAP may absorb 500 times its weight (from 30–60 times its own volume), but when put into a 0.9% saline solution, the absorbency drops to maybe 50 times its weight. The presence of valent cations in the solution will impede the polymers ability to bond with the water molecule.

The total absorbency and swelling capacity are controlled by the type and degree of cross-linking to the polymer. Low density cross-linked SAP generally has a higher absorbent capacity and swell to a larger degree. These types of SAPs also have a softer and more cohesive gel formation. High cross-link density polymers exhibit lower absorbent capacity and swell. The gel strength is firmer and can maintain particle shape even under modest pressure.

The largest use of SAP is found in personal disposable hygiene products, such as baby diapers, adult protective underwear and sanitary napkins,Absorbent Flood Defence Bags,
SAP was discontinued from use in tampons due to 1980s concern over a link with toxic shock syndrome. SAP is also used for blocking water penetration in underground power or communications cable, horticultural water retention agents, control of spill and waste aqueous fluid, artificial snow for motion picture and stage production.