So you probably know that some polymers' chains are getting broken when exposed to sunlight for a long time. Here I made a sign to prevent you and your friends to expose your filaments on sunlight. Not that they can melt but they can degrade and by degradation I mean getting brittle. You should see it on PLA, once it's exposed to the sun, it's easy to break and the PLA that is stored in darkness should remain flexible and not break upon bending :)