material attached underneath the hood

[BootzExplorer]

do you guys know what material it is that is right underneath the hood that is attached to the hood? it is above the engine. when you prop up the hood you look up you can see it. Well i had a lot of mud on it. I wanted to spray it, but i know if i spray it hard enough it will fall apart. if it does fall apart where can i get a new one? and i heard there was a heat resistant one. is there a water proof one?