Super absorbent polymer, also known as super absorbent, is a water swelling polymer with strong hydrophilic groups such as carboxyl and a certain degree of crosslinking. This paper briefly expounds the improvement methods of SAP powder.

1.Improve the water absorption rate of super absorbent polymer

The main driving force of water absorption of gel is the osmotic pressure difference caused by different ion concentrations inside and outside the gel network. Therefore, generally, the water absorption rate of non-ionic gel is much higher than that of ionic gel. The larger the surface area of gel, the faster the water absorption rate. The smaller the particle size of granular gel is, the faster the water absorption rate is. Making hydrogels into porous and fibrous shapes can not only increase the surface area, but also greatly improve the water absorption rate of super absorbent polymer due to capillary effect.

2.Improve the swelling gel strength of super absorbent polymer

The main methods to improve the strength of super absorbent polymer expanded gel are to improve the degree of crosslinking and introduce hydrophobic components into gel. Increasing the crosslinking degree is not conducive to improving the water absorption capacity. At the same time, it will reduce the elasticity of the expanded gel network and increase the brittleness. Therefore, this method is limited to improve the level of gel. Copolymerization with hydrophobic monomers forms nonpolar hydrophobic micro areas in aqueous solution, which are closely arranged and play the role of physical crosslinking, which is conducive to improving the tensile strength, enhancing toughness and reducing brittleness of the expanded gel. Some scholars also suggest adding inorganic materials to form composite reinforced gel. The commonly used inorganic fillers mainly include montmorillonite, kaolin, mica and bentonite.

3.Improve the electrolyte resistance of super absorbent polymer

Flory's elastic gel theory shows that the greater the ionic strength of the external solvent, the lower the absorption of the resin, which is far lower than that of deionized water. Its mechanism of action has two aspects: on the one hand, when absorbing salt water, the osmotic pressure inside and outside the network decreases; On the other hand, the existence of external ions inhibits the dissociation of ionic groups, and the network structure changes from extended to curled, which is the so-called salt effect and isoionic effect. The main method to improve the electrolyte resistance of super absorbent polymer is to introduce non-ionic monomers. The hydrophobic association of long-chain hydrophobic monomers makes the macromolecular chain cross-linked to produce a space grid structure with certain strength, giving it a large hydrodynamic volume and strong tackifying ability. The reversible space network structure produced by this hydrophobic association effect has strong resistance to inorganic salts and temperature damage; Synthesis of amphoteric polymers enables amphoteric ions to copolymerize comonomers, betaine amphoteric monomers, acrylamide, acrylonitrile, acrylic acid or acrylate, and then hydrolyze or neutralize them to give play to the synergistic effect of high absorption capacity of polyacrylate and good anti electrolyte performance of amphoteric polymers.

In recent years, the industrialization trend of global super absorbent polymer is rapid, and the market demand prospect is broad. Understanding the improvement methods of SAP powder can provide reference for its further development.