What is hard foam called?

Hard foam is commonly called rigid foam, closed cell foam, or hardboard foam depending on type. Most common hard foams are rigid polyurethane foam which is hard and used for insulation and structural support, extruded polystyrene foam known as XPS or Styrofoam which is hard and used for insulation boards, expanded polystyrene EPS which is hard but lighter used in packaging and cups, phenolic foam which is very hard and fire resistant used in insulation, and polyethylene foam in high density form which is hard. In construction, hard foam boards are called rigid foam insulation, foam board, or insulation board. In crafting, hard foam may be called floral foam, styrofoam, or high density EVA foam. Hard foam that hardens like concrete is called foamed concrete or rigid spray foam. So hard foam is generally referred to as rigid foam or closed cell foam, distinct from soft flexible foam like memory foam, and is used where structural support, insulation, and durability are needed rather than cushioning.