What types of high density foam for display bases/ dioramas?

[BigStick]

Hey All,
Looking for the type of foam used by Cosplay Chris in this video for a similar display base. Its not styrofoam because that stuff melts when you hit it with spray paint. I need stuff that is firm yet workable & spray paint safe. Video....

Thanks!

P.s. I've tried styrofoam primer & it was crap

 

[breen2057]

it might be Polyisocyanurate foam board used to insulate walls.

 

[BigStick]

Wow, thats a mouthfull. I’ll check it out. Thanks!