Sodium polyacrylate: My ♥ in pictures.
Dec. 17th, 2007 12:35 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
ldhensonTwo pictures taken on my desk, illustrating why I love this stuff so much.
Two small, clear spheres, both about a half-inch across, sitting in opposite corners of an acrylic dish. One sphere is glass, the other sodium polyacrylate.
Which is which?
With the addition of a little water...
The sphere on the right is glass.
I haven't taken anything out of the dish; I accidentally bumped it very slightly pouring the water in, but nothing was disturbed. Nothing dissolved, nothing reacted with the water in any way. The photo was taken immediately after the water went in. Needless to say I haven't doctored the photo.
What's happening?
Sodium polyacrylate is a super-absorbent polymer. Other people have explained it very well already, but in short it can absorb many many times its own weight in water, expanding greatly in volume as it does so.
The small sphere in the pictures above is already maybe 3/4 fully expanded. I chose the size to match with my small glass marble. In this example, however, it's not the additional absorption of water that does the trick. The absorption/expansion of this particular sphere is slow, so it's virtually negligible in the time it took me to pour the water and take the photo.
Since nearly all of the expanded volume is composed of absorbed water, the sphere now takes on the same optical properties as water, and "vanishes" from sight when submerged.
To sum up: sooo much fun.
Two small, clear spheres, both about a half-inch across, sitting in opposite corners of an acrylic dish. One sphere is glass, the other sodium polyacrylate.
Which is which?
With the addition of a little water...
The sphere on the right is glass.
I haven't taken anything out of the dish; I accidentally bumped it very slightly pouring the water in, but nothing was disturbed. Nothing dissolved, nothing reacted with the water in any way. The photo was taken immediately after the water went in. Needless to say I haven't doctored the photo.
What's happening?
Sodium polyacrylate is a super-absorbent polymer. Other people have explained it very well already, but in short it can absorb many many times its own weight in water, expanding greatly in volume as it does so.
The small sphere in the pictures above is already maybe 3/4 fully expanded. I chose the size to match with my small glass marble. In this example, however, it's not the additional absorption of water that does the trick. The absorption/expansion of this particular sphere is slow, so it's virtually negligible in the time it took me to pour the water and take the photo.
Since nearly all of the expanded volume is composed of absorbed water, the sphere now takes on the same optical properties as water, and "vanishes" from sight when submerged.
To sum up: sooo much fun.
