Yet another (polyisocyanurate) foam question

You can find at Home Depot an insulating foam called Polyisocyanurate. I cut off a little piece, took it home and laminated it with polyester resin. There was no melting or bubbling. Anybody have any thoughts on using this particular type of foam? Just playing around and wondering until the weather gets warm enough.


I’ve used it with polyester resin for stuff like fish boxes and coolers in commercial applications - works well for that, doesn’t react/turn to marshmallow fluff like styrene foams in the same circumstances. Oil and other petrochemicals either - used some to partly soundproof an engine box once.

I’d be kinda nervous about cutting it with a hot wire, 'cos there are cyanide compounds in there. Cuts and works well with standard tools, doesn’t melt or gum up particularly.

Not real flexy, takes adhesives well, yellows and crumbles somewhat in sunlight and weathering: my two year ‘put a coupla sheets over the lumber pile’ test. Didn’t have any other foams for comparison, just had a sheet left over from a job one time and needed to cover the wood. .

Uniform density throughout, dunno how they make it in sheets, cut from bigger billets or what.

As an insulation foam it has a slightly higher R value [ 7 per inch vs 6 ] than polystyrene insulation foams. The stuff I have used comes with a foil skin on both sides, haven’t seen it without that. Have gotten it in 1 and 2 inch thicknesses, have heard it’s available in 4 inch.

That’s pretty much all I know about it. Hope that’s of use


Thanks Doc, it helps.

thats basically the same as polyurethane in standard board foam except its a yellowy colour ,sometimes green …

toulene di isocyanate or tdi as its refered to is standard surfboard foam …its toxic coz its white and clean ,the poly isocyanate is similar but not as toxic but looks ugly ,im sure some of you old time board builders used to use it years back??

did it pass the test for durability???i have seen some real old boards built from it dating back to late sixties…ive never had any experience using it myself so i dont know of any drawbacks /advantages???