Stick down sound proofing ,Insulation?

I'm going to wait 'till I drive this a car again on a warm day and see how hot rear floor gets -dual mufflers are right there. I stuck some of the mat on a piece of plywood and laid on top of my kerosene heater - as it heated up the butyl rubber got pretty gooey...have to say no odor to it though: If floor get s super hot I might forego the mat there.
Interesting. Did the mat seem to block the heat at all? Did it solidify again after it cooled down?