Insulating Blanket

[Rob58]

My 58 year old aircraft has some type of fiber based insulating blanket as shown in the attached photos. This material is laid all over the lower interior skin of my plane (soaking up various fluids over the years). So suspicious that this stuff might be flammable I did my own testing with a little piece... well, it lit off like the 4th of July. Wow; scary. I'm curious if this material was widely used back in the '50s and '60s and what was its main purpose... sound insulation? Thermal insulation? What modern material would be a good replacement? Any feedback is really appreciated!

 

[bluerooster]

Based upon the pic in your avatar, and those posted. I kinda doubt that was factory installed. It kinda favors the appearance of old carpet pad.
Was probably installed as sound deadening material.
What's it made of?