I believe its a structural foam as opposed to a lighter open cell which is only intended as a layup
support. The use of light urethane foams in composite aircraft revealed it crumbling to dust when exposed to vibration and UV after only a few years, and it wasnt just a health
concern with the micro beads being airbourne but also for avionics.Ive used DOW floor insulation
structural foam as a laminate layup
support but only with epoxy
resins as its disolved by styrene.