How do superabsorbent polymers work?

What is super absorbent polymer?

SAP (Super Absorbent Polymer) are classified as hydrogels when cross-linked, absorb aqueous solutions through hydrogen bonding with water molecules. In deionized and distilled water, a SAP may absorb 300-1200 times its weight and can become gel, but when put into a 0.9% saline solution, the absorbency drops to maybe 50 times its weight.

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

How it works?

It consists of a set of polymeric chains that are parallel to each other and regularly linked to each other by cross-linking agents, thus forming a network.

When water comes into contact with one of these chains, it is drawn into the molecule by osmosis. Water rapidly migrates into the interior of the polymer network where it is stored.