How do diapers absorb

The secret of the baby diaper

There are materials that absorb liquids really well. They are said to "absorb" the liquid. Others, on the other hand, simply let water roll off. By experimenting with water and various solids, you can see for yourself why that is the case.

Infobox

You need this:

  • 4 wide glasses or glass bowls
  • small stone with a smooth surface
  • Cling film
  • Cotton wool
  • small plastic cup
  • Felt pen
  • A4 sheet (preferably in a dark color, e.g. blue)
  • 1-2 disposable baby diapers
  • scissors

How to do it:

  1. Place a stone, a piece of crumpled-up cling film, and some cotton wool in a glass. Fill the small plastic cup with water about a finger's width, mark the water level and pour exactly as much water into each glass.

  

  

Closely observed:

The stone is not absorbent at all. Cling film does not absorb water, but it retains it drop by drop on the surface. Cotton absorbs water, but when you press it, the water flows out again.

And what's in the baby diaper?

  1. Fold the colored A4 sheet into a bowl by folding up the edges about 2 cm. Put a disposable diaper inside.
  2. Cut up the diaper and use the paper tray to catch the beads that fall out.
  3. Put the beads in a glass and add the same amount of water as before.

Observed closely:

It takes a few minutes, but then the globules soak up water. A kind of gel is created. This gel is firm and retains the water even under pressure. You can also try using an intact diaper to see how much water you can pour on it without it feeling damp. Amazing isn't it?

What's behind it?

The water simply runs down the smooth surface of a pebble, as does the plastic cling film. But since you have crumpled up the foil, individual drops get stuck in the gaps. Cotton wool consists of many fine hairs between which water is held. If you squeeze out the wet cotton wool, the gaps will close. The water drips out again.

The absorbent beads in the baby diaper are made of a special plastic. Such plastics are called "super absorbers" because they are "super-strong" in absorbing water. This plastic has the property of forming a network with water particles. The network of plastic and water feels like a gel. The water no longer loosens from the anchorage even under pressure.

Source: SGCI Chemie Pharma Schweiz
Idea: Prof. Dr. Gisela Lück, Bielefeld University
Cooperation & support: Siegfried Ltd., Max Widmer

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