Why does transparent plastic become opaque when it breaks?

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My 7yo snapped the clip off of a transparent pink plastic pen. He noticed that at the place where it broke, the transparent pink plastic became opaque white. Why does that happen (instead of it remaining transparent throughout)?

This is best illustrated by the pic I took of the [broken pen](https://imgur.com/S8rasqb).

In: Physics

13 Answers

Anonymous 0 Comments

Polymers are made of of many “mers”. These are chains of atoms. Normally they are randomly oriented and amorphous. When you bend or stretch plastic you are aligning these polymer chains which causes the optical properties to change.

Fun experiment. Go find a plastic shopping grocery bag. stretch the bag and watch it turn white.

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