To absorb means to "take in". So absorbers absorb something - in the case of Klein-Erlenmeyerchen's diaper mainly water. Superabsorbents absorb a lot of water, and the result is: the diaper stays dry. No rocket science, but exciting chemistry 1,2.
Superabsorbents are made up of long-chain molecules, so-called polymers. These polymers are created by linking a large number of small acrylic acid units and similar compounds. They form long threads. We can imagine our superabsorbent in the dry state like a ball of such threads ( A ) 3.
Due to their special shape, the acylic acid balls are now able to absorb a great deal of water, about a thousand times their weight in the case of pure water. Of course, they swell up tremendously ( B ).
Such a superabsorbent is on the market as a white, coarse-grained powder. It is not only used in diapers, but also in other hygiene articles, in extinguishing agents, in potting soil and in many other products. A creative mind has even constructed a self-sealing door with superabsorbents like this - a good idea in times of heavy rain! 4th
Like all polymers, polyacrylic acid is also a plastic that is difficult to break down. So we have to be careful that it does not end up in the wastewater and thus ultimately lead to serious problems in the oceans. The full diaper is therefore best stored in the residual waste. It is properly burned in most countries.
Superabsorbents could also be made from readily degradable polymeric natural substances such as cellulose, gelatine or starch 5,6. That would kill two birds with one stone: Crude oil, the raw material for polyacrylic acid, would be avoided and the product would be easier to break down if it got into the sewage system.
Literature:
[1] Superabsorbents in Wikipedia
[2] Superabsorbents: Crazy chemistry in the diaper, YouTube
[4] K. Günthner: Flood protection - self-sealing doors and windows with the help of super absorbers. At DocPlayer
[5] M. Zeuke: Superabsorbents made from renewable raw materials. The targeted synthesis with renewable raw materials, CHEMKON 2005, 12, 155.
[6] M. Lechner: Superabsorbents based on renewable raw materials.
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last modified: 06.07.2021 20:29 H from MPM
