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Have you ever seen the magic "disappearing water"? The magician poured water into the cup, and then turned the bottom of the cup up, and the water in the cup did not flow down. So what is this magic principle that makes water disappear? Learn about the key to this magic today - SAP powder

1.Super absorbent properties of SAP powder

Where did the water in the cup go in magic? It turned out that there was a powder hidden in the cup, called SAP powder. It is a new type of functional polymer material that can absorb water that is hundreds or even thousands of times its own weight. When it absorbs water and swells, it solidifies with water and becomes a hydrogel with super strong water-locking ability, so the water cannot flow out, and it will not leak even if it is squeezed hard.

Paper towels, towels and sponges are all materials used to absorb water in daily life. They can absorb up to 20 times their own weight in water, and the water retention is not strong, and the water can be squeezed out by pressing hard. In front of SAP powder, they are all insignificant. Similar to materials such as paper, cotton and sponge, its water absorption capacity is also mainly achieved through the strong hydrogen bonding between hydrophilic genes such as carboxyl and hydroxyl groups and water molecules. The difference is the amount of hydrophilic genes available for the latter. It is much higher than the former, and the molecular chain grid structure can be highly swelled, which further binds water molecules in it, thereby obtaining super water absorption performance.

2. Where does SAP powder come from?

What does SAP powder have to do with a potato? In fact, the starch rich in potatoes can be its source. Starch is generally insoluble in water, but when heated in water, the weak hydrogen bonds in the crystalline area are destroyed, the crystalline area disappears, hydration and swelling begin, and the viscosity increases. This phenomenon is called gelatinization.

The starch used to prepare it is mainly corn starch and wheat starch, and starch of potatoes, sweet potatoes and rice can also be used as raw materials. Technology is always developing according to the needs of human life, and the method of preparing SAP powder from starch has been continuously improved, and now it has become a relatively mature and convenient technology. Not only starch, but also natural polymers such as cellulose and chitosan are good sources.

Another important source of it is synthetic polymers such as polyacrylic acid (PAA), polyacrylamide (PAM) and polyvinyl alcohol (PVA). Polyacrylic acid and sodium polyacrylate, which are the most widely used water-retaining agents, have excellent water absorption and water retention capabilities. Polyvinyl alcohol (PVA) has similar water absorption to polyacrylic acid, and can also be degraded with the help of bacterial enzymes, greatly improving its application value.

In general, natural resins such as cellulose, starch, and chitosan have advantages in terms of degradability and biocompatibility, which can avoid environmental pollution. But their extraction and modification process is more complicated, and the production cost is higher than some synthetic polymers. Synthetic resins usually have the advantages of lower cost, longer service life and higher water absorption than natural polymers, but they are difficult to degrade and easily cause environmental pollution. Therefore, scientists continue to explore and try to combine the advantages of natural polymers with synthetic polymers to obtain better application prospects.

Based on the unique characteristics of SAP powder with strong water absorption and high water retention, it has found use in many fields. In daily life and hygiene products, the use of baby diapers, feminine hygiene products, etc. is the most common. Knowing about SAP powder will help people better understand and use this material.