Super Absorbent Polymer, What is it ?
Super Absorbent Polymer
Super absorbent polymer(SAP) is a new type of functional water absorbing crystals. It is a synthetic polymer material with hydrophilic groups, which can absorb a large amount of water, swell and keep the water from flowing out. The superabsorbent polymers can generally absorb water equivalent to more than 100 times the volume of the SAP, and the highest water absorption rate can reach more than 1,000 times. Generally, it is used as medical materials, such as diapers and sanitary napkins, which are also used as plugging materials in the industry.
Principle of Water Absorption
This materials that absorb water (SAP) is generally a polymer electrolyte containing a hydrophilic group and a crosslinked structure. Before absorbing water, the polymer chains are entangled with each other and crosslinked with each other to form a network structure, thereby achieving overall fastening. When in contact with water, water molecules penetrate into the resin through capillary action and diffusion, and the ionizing groups on the chain are ionized in water. Due to the electrostatic repulsion between the same ions on the chain, the polymer chain stretches and swells. Due to the requirement of electrical neutrality, the counterions cannot migrate to the outside of the resin(instead of super absorbent polymer), and the difference in ion concentration between the solution inside and outside the resin forms the reverse osmotic pressure. Water further enters the SAP under the action of reverse osmotic pressure to form a hydrogel. At the same time, the cross-linked network structure and hydrogen bonding of the resin itself limit the infinite expansion of the gel.
After neutralizing acrylic acid or sodium acrylate with alkali, adding a pre-crosslinking agent and initiator to carry out the polymerization reaction. Then drying and crushing after obtaining the hydrogel, and crushing gel particles during the crushing process will also produce dispersion fine powder. Secondary granulation of the fine powder, adding fumed silica during the secondary granulation process and then granulating together with the crushed gel particles. The resulting granulated material is mixed with water and post-crosslinking agent surface treatment in the heat treatment liquid, that is, a highly absorbent polymer.
High-molecular water absorbing material is a net-shaped polymer non-toxic polymer with strong water-absorbing properties.
1) Hygiene products: sanitary napkins, diapers, diapers, absorbent paper, etc.
2) Industry: Water-proof swelling rubber, water-absorbing antifouling coating, anti-condensation coating, antistatic coating, oil field water blocking and oil-water separation, optical cable with tape and cable paste, etc.
3) Medical: medical disposable underpads, hemostatic bandages, slow-release drugs, ice packs, etc.
4) Agriculture and gardening: soil water retention, seed coating, seed dressing.
Keywords: superabsorbent, superabsorbent polymer, SAP
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