PIR Foam? Is it xps?

General Discussion
1

Following on from another thread I am on the search for a suitable foam core for a compsand board. Locally all i can get is 0.9lb EPS as it is so rarely used nowadays here. 

Nearly all insulation here in the uk is PIR boards. I had assumed these were extruded polystyrene but it seems they are not? The wikipedia entry from it seems to imply its similar to PU 

Can anyone shed any light on this? Would it make a suitable core? Will epoxy glassing adhere to it?

Here is the blurb from wikipedia

Polyisocyanurate, also referred to as PIR, polyiso, or ISO, is a thermoset plastic[1] typically produced as a foam and used as rigid thermal insulation. Its chemistry is similar to polyurethane (PUR) except that the proportion of methylene diphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol. Catalysts and additives used in PIR formulations also differ from those used in PUR.

 

Thanks

2

What is the density, kg/m3 or lb/ft3?  Is the density uniform, surface to center?

Get a small piece of it and see how well it bonds with epoxy.

3

Its 26 kg/m3 don’t know about the variable density?

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4

http://www.swaylocks.com/groups/yet-another-polyisocyanurate-foam-question

not much info but its something…

5

PIR is neither EPS nor XPS.  It looks to be most like PU.

Did some reading.  Made from similar chemicals used for PU.  The advantage appears to be that PIR is more heat tolerant than PU.  

Rated as putting out more toxic gas than PU when burned.  Makes hotwiring dangerous.

Can you get it without the metal sheathing?

26 kg/m3 would be roughly 1.6 lb/ft3 (pcf).  I will let the compsand builders tell you whether or not this is a good density for veneer builds.

6

​yes thanks I read that old thread. I assume this is not common then on your side of the pond.

7

Pir is more or less pur. Don’t use hotwire, toxic gas.

8

1.6# or 2# closed cell foam would work even better for a compsand than EPS.  I’ve done several veneers over PU foam (also closed cell) and that’s a great strength/weight combo.    

With EPS if you get a ding out in the water the core will soak it in like sponge by the time you paddle the board in.   But with closed cell foam the water intrusion is localized around the leak, and is way easier to completely replace/repair.