Hydrogels are manufactured substances that absorb liquid and hold it in the form of gel. Sometimes, they are called ‘moisture-absorbing-cystals’ or if you want to get super-technical here, ‘super-absorbent-polymers’.
The most common products you will find hydrogels are:
- Disposable Nappies
- Sanitary Towels
- Wound Dressings
Most commonly you will find hydrogels in disposable nappies, sanitary pads and wound dressings. But let’s focus on nappies….There are different types of hydrogels and the most commonly used you’ll find in nappies are called sodium polyacrylate. You’ll probably guess why hydrogels are used in nappies – they’re super-absorbent – meaning that they will soak up all the baby’s wee and keep them (and you) dry.
There’s a cool simple science experiment that you can do to see how much these tiny hydrogels actually absorb and all you need is a disposable nappy (clean!), a pair of scissors, a stirrer and two cups – one empty and one filled with tap water.
- With the scissors, carefully cut the middle section of the nappy in half – aim for the thicker piece that is designed to absorb all the urine. You only need one half.
- You will see the fluffy white material in-between the layers and if you look carefully, very small white beads. Start pulling this material away and place it in the empty cup. Pull away as much as you can for this experiment to be effective.
- Estimate the volume of the material in the cup and pour water to fill ¾ of the cup filled with the nappy contents. Pour enough until no more can be absorbed and stir.
- You will begin to start seeing tiny solid gel-like particles in the cup, which is the process of how the hydrogels have absorbed the liquid.
The Science bit:
If we're going to be super-sciencey then this is the actual scientific formula of how this hydrogel process works:
The hydrogels are polymers that can hold many times it's own weight in water (hence why they are great for nappies). The polymers are made up of carboxylic acids that ionise when submerged in water, which means the polymer will have several negative charges down its lenth. This gives off two effects. The first negative effects repels each other and the polymer is forced o expand. Secondly, the polar water molecules are attracted to the negative charges, which increases the viscosity of the developing mixture further as the polymer chain now takes up more space and repels the flow of the solvent molecules surrounding it.
This is a great little science experiment to teach your children, and really gives them an understanding exactly how they were kept so dry as babies and made your lives easier as their designated nappy changer!
Source: Baby Centre