Superabsorbent polymer, also known as superabsorbent resin, is a new polymer material with three-dimensional network structure function. It contains strong hydrophilic groups such as hydroxyl and carboxyl groups and has certain cross-linking property. It has super absorbent and water retaining capacity, and can absorb hundreds of times or even thousands of times its own weight. Gel can be formed within a few seconds, and its water retention is strong. It is not easy to lose water when heated and pressurized, and has good stability to light, heat, acid and alkali, good biodegradability, and good advantage of polymer materials. SAP is widely used in forest, horticulture, industry, medical treatment, sanitary napkin, sand prevention, waterproof and other fields. As a water absorbent material, SAP constitutes the core of pull-up pants and toddler pants composite core.
The test results of absorption time and drying time can directly represent the speed of pull-up pantsabsorbing liquid, and the drying time can directly represent the drying time of the layer behind 22 absorbing liquid, which is an important index to evaluate the comfort of pull-up pants.
Cr-630 resin used in the experiment is polyvinyl alcohol acrylate block copolymer, which belongs to porous salt resistant super absorbent resin. From the perspective of chemical structure, its main chain or grafted side chain contains strong hydrophilic functional groups such as carboxyl group and hydroxyl group. The affinity between these hydrophilic groups and water is the main internal cause of its water absorption; From the perspective of physical structure, in order to achieve its high water absorption, the resin must have a three-dimensional network with low crosslinking degree, and the network skeleton is synthetic resin (polyacrylic acid); From the perspective of microstructure, porous salt resistant superabsorbent resin forms porous network structure after absorbing water, which is of great significance to improve its water absorption performance.
Expantsion process of super absorbent sap in water sap is a polymer with three-dimensional space network, which is formed through appropriate crosslinking. Its hydrophilic and hydrophobic basis interacts with water molecules. When the polymer is hydrolyzed, the electrostatic charge on the polymer chain increases rapidly. It is this electrostatic repulsion that gradually expands the three-dimensional network and guides water molecules into the resin. At the same time, in order to maintain electrical neutrality, another charge competing with the charge accumulated on the polymer chain will not diffuse to the outside, but bound inside and outside the resin network, forming a large concentration difference, generating a large osmotic pressure, and further absorbing water molecules into the three-dimensional network. With the expansionof the network, the elastic contraction of the three-dimensional network will gradually increase. As a kind of competitiveness, it will slowly offset the electrostatic repulsion, and finally make SAP reach the water absorption balance.
Therefore, the water absorption capacity of super absorbent resin can be regarded as the result of the expansion caused by the ionic charge of polymer electrolyte in water and the interaction of cross-linking structure and hydrogen bond. There is no doubt that the material has an impact on the properties of pull-up pants and toddler pants.
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