Water-absorbent polymers or hydrogels are water-insoluble hydrophilic polymers, able to swell and absorb amounts of water, saline solutions, or physiological fluids as high as 10-1000 times their own weight. They consist of polyelectrolytes or other highly hydrophilic polymeric matrices, usually bearing crosslinking sites along the macromolecular chains in order to avoid dissolution. These polymers generally contain carboxylic groups that are in equilibrium with their dissociated form in the presence of water or carboxylate groups. The polymer coils extend themselves and widen in consequence of the electrostatic repulsion of negative charges. Carboxylate groups are also able to interact through hydrogen bonding with additional quantities of water.
Water absorbent polymer (also referred to as slush powder) is a polymer which will absorb and retain extraordinarily massive amounts of a liquid relative to their own mass. Water gripping polymers that are classified as hydrogels once cross-linked, absorb liquid solutions through chemical element bonding with water molecules. An SAP’s ability to soak up water could be an issue of the ionic concentration of the solution. The largest use of water absorbent is found in personal disposable hygiene merchandise, like baby diapers, adult protecting underclothes and sanitary napkins.