Why do transparent phone cases turn yellow after a while?

Question

Note that this happens even if the phone rarely exposed to the sun light

In: Chemistry

Answer 1

The transparent phone cases are often made of polyurethane. When exposed to UV light, polyurethane can degrade and become oxidized, turning into yellow-ish compounds called quinones.

Answer 2

Just like the sun’s UV rays damage our skin and turn it red, they make plastic polymers yellow through cell damage

Answer 3

You’re washing your hands after you pee, right? Right?!