A thermoset plastic is a nonmeltable plastic that was made by melting down a powder and when that happens, all the little plastic molecules theoretically combine to make one giant molecule. This is why you cant remlt it, all that would happen if you tried to melt the thermoset plastic, is the plastic would burn away. Think of it like this: think of roaps, and that each rope is a molecule, when you tie the ropes together you can pull them apart, think of that al melting normal plastic together, in that it still has a melting point where the molecules come apart. Now if you were to weave each strand together that makes up the rope, you wouldn't be able to pull it apart. Teoretically that's what happens in thermoset plastic, all the molecule come together and form a giant one. So that means we can think of the hood of a big rig to be one giant molecule.