Submitted by Athousandlipsticks t3_10bvhgz in askscience
I’m trying to melt those white plastic bags and using a heat gun for this, however strangely enough the plastic just warps and then solidifies into a very hard substance rather than melting first. Can anyone explain to me why?
thenopebig t1_j4cz6sh wrote
Well I don't know what plastic you are working with, but my guesses are that it is a thermosetting polymer. Basically, picture polymers as chains of molecules that are weakly bonded. In some cases, heating the plastic will push the molecules to create hard covalent bonds between themselves called crosslinks, which causes these plastics to irreversibly harden. You will not be able to melt it, or even reshape it.