mapt 4 hours ago

The R-value performance numbers for asbestos as building insulation are wildly divergent, but most of them aren't especially competitive with modern materials.

I'm not sure how to square that with claims like:

> With phenolic resins, asbestos products are produced which will provide insulation and retain strength when subjected to 5,000°F for periods of minutes (1 to 30 minutes) . See Figure 2.1 in which a rocket motor part is subjected to a temperature of 5,000°F. Figure 2.1. Rocket motor aft (asbestos-phenolic insulator) before and after firing at 5,000°F.

> The temperature approximately 1/8 in. from the surface exposed to 5,000°F will be approximately 200°F after 1/2 to 1 min. of exposure.

> When combined with magnesium carbonate and other similar products, heat insulators can be produced which will be useful for many years in such applications as boilers operating at temperatures from 500° to 1,200°F or 1,800°F.

We seem to use a matted "Ceramic Fiber" roll for its high-heat insulation capabilities these days, up to about 2300F-2600F depending on type. Asbestos fiber insulation seems to be good to somewhere between 1500F to 2700F depending on how you use it. Ceramic fiber is carcinogenic in a similar way to asbestos, but apparently considerably safer due to the fiber length/alignment.