Insulating the hull questions.

[ebb]

Seems that all named Armaflex ntrile foams are closed cell. (HT, NH, UT, AR, etc.)
Buna-N, NBR, Nitrile is a copolymer of butadiene and acrylontrile (ACN). These are tweaked for elasticity and crosslinking during sulphur vulanization....as well as for tensile strength, hardness, abrasion resistance and vapor impermeability. "The ACN content of Nitrile rubber material can range from 16% to 45% with a general purpose compound usually containing around 34%...." www.timcorubber.com/rubber-materials/nitrile.htm

Which is simply to pointout that even AP-Armaflex formulations will produce different foams. Small cell, large cell and different foaming gases.... with Armacell - on the green side - using carbon-dioxide as the blowing agent. Nitrile's main attribute is it's broad range resistance to petrochems and solvents (except aromatics.*)

Maybe temperature and moisture cycling of foam in use tends to break down some formulas and not others. There are different types of nitrile yielding highly branched, or linear, or crosslinked (AR-Armaflex) polymers. Which is to say that maybe not all Armaflex products over the years are the same.
While nitrile foam is kown for its resistamce to many chemicals, it has a poor reputation for weather resistance. Ozone & UV. you can't leave it uncoated when used outdoors.
And there could have been bad batches, as you say - that Armacell doesn't admit to.
There could have been an Armacell foam used in your HVAC installaions that is not an AP-Armaflex.
Synthetic plastic rubber is not glass or stainless steel. Imco there always has to be the possibility of water or some vapor migrating thru plastic - given certain specific conditions.


google: Armacell - Shell Deer Park, Houston Texcas
Where two 82' diameter spheres (containing continuously cooled butadiene at near freezing) were covered in 3" of AP-Armaflex.
The whole point is to control the temp of the contents (3" of Armaflex has an R value of 8.4)
The spheres were first coated with a fire proofing epoxy that itself expands into foam at very high temps.
Would think that the glue for the Armaflex has to be something more than mere contact cement.
After the spheres were covered with AP-Armaflex, a blanket of UV rubber coating was sprayed over the foam.
This is a highly engineered installation, these petro guys aren't fooling around.
Has to be guaranteed to last at keast few years in Texas sun and weather...


Imco, the word INTERCONNECTED ususlly refers to OPEN CELL foam.
The gas bubbles in closed cell foam aren't connected.
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* If any of these solvents listed here were used to prep or clean parts of a HVAC install, they could have attacked nitrile AP-Armaflex:
turpentine, rubber solvent C9, benzene, and xylene, naptha, toluene. Xylene is a constituent of gasoline.

Solvent based CONTACT CEMENT is likely to be formulated with some aromatic solvents - chemicals that can brealdown nitrile rubber.
(So, for example, if the cement is encapsulated in closed cell nitrile foam pipe wrap.....and the solvent cannot escape
.....the solvent in that scenario might eat the rubber and open closed cells into a sponge.)