Re: Why does plastic turn white before it breaks?

Good observation!

When you bend the plastic you are actually stretching it a little at the point of the bend. This causes the plastic to pull apart and tiny voids [holes] are formed. Since the plastic is at room temperature, it cannot flow in to fill the voids.

Although the voids are very small, they are still big enough to refract light and the light, instead of passing through the plastic making it appear clear, gets partially - or mostly - reflected back to our eyes making it appear white and opaque.

The color doesn't 'go' anywhere -- it is just masked by the domination of the white voids.