ForMatter/Materials/polymer/Extruded Polystyrene Foam (XPS)
mat_xps_foam

Extruded Polystyrene Foam (XPS)

thermoplastic foam — closed-cell, extruded · XPS, pink foam, blue foam, Styrofoam Brand (Dow), extruded styrofoam
mediumlast updated 2026-04-28
metallic 0.00
hue shift +0°

The pink (or blue) board every architecture school stocks for site models. Extruded as one continuous closed-cell loaf, denser and less crumbly than EPS, sands and cuts cleanly with a knife. Comes in 1/2-inch and 1-inch and 2-inch sheets, slices like cake. Acetone destroys it; water-based glue and spray-mount are safe.

Polystyrene extruded with a blowing agent into a uniform closed-cell foam, ~30–35 kg/m³. Higher compressive strength than EPS at equivalent density (200–700 kPa). Lower thermal conductivity than EPS (k ≈ 0.029–0.033 W/m·K). Color (pink, blue, green) is brand-tracer-only — Owens Corning Foamular pink, Dow Styrofoam blue, Kingspan green; the polymer is identical.

physical

  • density_kg_m332
  • compressive_strength_kpa240
  • thermal_conductivity_w_mk0.031
source: Wikipedia — Extruded polystyrene foam

Sustainability

  • recyclabilitylow — recycle code 6, rarely curbside; HFC blowing agents historically a concern (now phased out for HFOs in most markets)
  • biodegradableFalse
  • certificationsGreenGuard Gold (some Foamular grades)
visual
uniform tinted pastel — pink, blue, green by brand — no visible bead structure
tactile
cool, even, less squeaky than EPS, slightly waxy
weight perception
almost nothing
acoustic
a soft scrape under a knife; cuts almost silently

PBR starter values

Principled BSDF defaults derived from the sphere granular finish. Reasonable seed for Blender, Substance, Keyshot, Rhino — tune per material.

# finish:      granular
albedo        #e890a8
metallic      0.00
roughness     0.85
ior           1.45
transmission  0.00
clearcoat     0.00
sheen         0.00
anisotropic   0.00
copy as JSON 
{
  "albedo": "#e890a8",
  "metallic": 0.0,
  "roughness": 0.85,
  "ior": 1.45,
  "transmission": 0.0,
  "clearcoat": 0.0,
  "sheen": 0.0,
  "anisotropic": 0.0
}
Blender 4.x Python 
# Blender 4.x — Principled BSDF
# Extruded Polystyrene Foam (XPS) · finish: granular
import bpy
mat = bpy.data.materials.new(name="mat_xps_foam")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value         = (0.807, 0.2789, 0.3916, 1.0)
bsdf.inputs["Metallic"].default_value           = 0.000
bsdf.inputs["Roughness"].default_value          = 0.850
bsdf.inputs["IOR"].default_value                = 1.450
bsdf.inputs["Transmission Weight"].default_value = 0.000
bsdf.inputs["Coat Weight"].default_value        = 0.000
bsdf.inputs["Sheen Weight"].default_value       = 0.000
bsdf.inputs["Anisotropic"].default_value        = 0.000
KeyShot Python (lux) 
# KeyShot 11+ — lux Python API, Generic material
# Extruded Polystyrene Foam (XPS) · finish: granular
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_xps_foam", materialType="Generic")
mat.setProperty("diffuse",      (232, 144, 168))   # 8-bit sRGB
mat.setProperty("metallic",     0.000)
mat.setProperty("roughness",    0.850)
mat.setProperty("indexOfRefraction", 1.450)
mat.setProperty("transparency", 0.000)
mat.setProperty("coatingWeight", 0.000)
Substance pbrMetalRough 
{
  "_format": "Substance Designer / Painter \u2014 pbrMetalRough constants",
  "_about": "Extruded Polystyrene Foam (XPS) \u00b7 finish: granular",
  "baseColor": {
    "r": 0.807,
    "g": 0.2789,
    "b": 0.3916
  },
  "metallic": 0.0,
  "roughness": 0.85,
  "ior": 1.45,
  "opacity": 1.0,
  "anisotropyLevel": 0.0,
  "_notes": "Channels listed are the standard Substance pbrMetalRough output. Drop into a Uniform Color node per channel, or as the constant input on a layered stack."
}
glTF 2.0 Metallic-Roughness 
{
  "asset": {
    "version": "2.0",
    "generator": "ForMatter"
  },
  "materials": [
    {
      "name": "mat_xps_foam",
      "pbrMetallicRoughness": {
        "baseColorFactor": [
          0.807,
          0.2789,
          0.3916,
          1.0
        ],
        "metallicFactor": 0.0,
        "roughnessFactor": 0.85
      },
      "extensions": {
        "KHR_materials_ior": {
          "ior": 1.45
        }
      }
    }
  ]
}
USD Preview Surface 
# USD Preview Surface — UsdShade.MaterialLook prim attributes
# Extruded Polystyrene Foam (XPS) · finish: granular
def Material "mat_xps_foam" {
    token outputs:surface.connect = </mat_xps_foam/PreviewSurface.outputs:surface>

    def Shader "PreviewSurface" {
        uniform token info:id = "UsdPreviewSurface"
        color3f inputs:diffuseColor = (0.807, 0.2789, 0.3916)
        float   inputs:metallic     = 0.000
        float   inputs:roughness    = 0.850
        float   inputs:ior          = 1.450
        float   inputs:opacity      = 1.000
        float   inputs:clearcoat    = 0.000
        token   outputs:surface
    }
}
↓ download glTF material
ProcessCNC Milling · Hot-Wire Foam Cutting
Used inPrototype / Concept Model
Substitutes
Expanded Polystyrene Foam (EPS)
Polyurethane Foam (flexible, upholstery)

Citations