And how are they made?
In: Chemistry
Solid materials have stable forms that they’re resting in. Most materials can be bent or squished or deformed to a certain extent and then they will return to their stable state because you didn’t force them to change too much.
Imagine a material like foam being made up of millions of tiny rubber bands tied to each other. They stretch a little. The same goes for other materials like metal too. The formal name for this is called “elastic deformation”.
However, if you apply too much change to a material, some of those millions of rubber band bonds kind of… snap. And then the material cannot return back to it’s original shape because it went past the stretching point. This is formally called “plastic deformation”.
So the thing about foam like that used in earplugs, is that it has an enormous range of elasticity before it will deform plastically. Just like a rope net that’s been rolled into a ball, the original shape is maintained, just bundled up.
Squishy things that retain their shape (take play-doh as an example) are composed of a bunch of long molecules that can slide past each other. When the pressure is released they do not return to their original arrangement since they have slid into new positions.
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