ForMatter/Materials/polymer/Silicone Rubber (RTV)
mat_silicone

Silicone Rubber (RTV)

elastomer, thermoset · silicone, PDMS, RTV silicone, polydimethylsiloxane
mediumlast updated 2026-04-26

The rubbery, slightly squishy material of phone cases, kitchen spatulas, gaskets, and prototype-shop mold-making. Pours as a liquid, cures into a flexible solid in hours at room temperature. Heat-resistant well beyond what other rubbers can take.

Polymer with a silicon-oxygen backbone (siloxane), distinct from carbon-backbone elastomers. Room-temperature-vulcanizing (RTV) grades cure via tin or platinum catalysis. Excellent thermal stability (-50 to +250 °C), inert, biocompatible (medical-grade platinum-cured), poor adhesion (an asset for mold-release).

Mechanical

  • tensile strength · MPa7
  • elongation · %400
  • hardness Shore a30
source: Smooth-On Mold Star 30 datasheet (representative)

Thermal

  • service range · °C-50 to 250
  • thermal conductivity · W/m·K0.2
source: Smooth-On

Sustainability

  • embodied carbon · kg CO₂e/kg5.5
  • recyclabilitylow — thermoset, cannot be remelted; some grinding-and-reuse as filler
  • biodegradableFalse
  • certificationsUSP Class VI (medical-grade, platinum-cured)
source: Editorial estimate from ICE / Granta CES EduPack class databases — industry mean, with cradle-to-gate boundary unless otherwise noted. Embodied carbon for any specific product depends on supplier mix, recycled content, and energy grid; verify against a primary source before using these numbers in a sustainability claim.
visual
translucent in unpigmented form, accepts bright colors when dyed
tactile
soft, slightly sticky, drags against itself, slips against most other surfaces
weight perception
light
acoustic
silent on impact — the material used to deaden sound in many products

PBR starter values

finish · matte — open for table, JSON, host snippets, downloads

Principled BSDF defaults derived from the sphere matte finish. Reasonable seed for Blender, Substance, Keyshot, Rhino — tune per material. Or grab the whole library at once: ForMaterials library →

# finish:                   matte
albedo                      #e0d8d0
metallic                    0.00
roughness                   0.75
ior                         1.45
transmission                0.00
clearcoat                   0.00
sheen                       0.00
anisotropic                 0.00
copy as JSON 
{
  "albedo": "#e0d8d0",
  "metallic": 0.0,
  "roughness": 0.75,
  "ior": 1.45,
  "transmission": 0.0,
  "clearcoat": 0.0,
  "sheen": 0.0,
  "anisotropic": 0.0
}
Blender 4.x Python 
# Blender 4.x — Principled BSDF
# Silicone Rubber (RTV) · finish: matte
import bpy
mat = bpy.data.materials.new(name="mat_silicone")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value         = (0.7454, 0.6867, 0.6308, 1.0)
bsdf.inputs["Metallic"].default_value           = 0.000
bsdf.inputs["Roughness"].default_value          = 0.750
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
# Silicone Rubber (RTV) · finish: matte
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_silicone", materialType="Generic")
mat.setProperty("diffuse",      (224, 216, 208))   # 8-bit sRGB
mat.setProperty("metallic",     0.000)
mat.setProperty("roughness",    0.750)
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": "Silicone Rubber (RTV) \u00b7 finish: matte",
  "baseColor": {
    "r": 0.7454,
    "g": 0.6867,
    "b": 0.6308
  },
  "metallic": 0.0,
  "roughness": 0.75,
  "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_silicone",
      "pbrMetallicRoughness": {
        "baseColorFactor": [
          0.7454,
          0.6867,
          0.6308,
          1.0
        ],
        "metallicFactor": 0.0,
        "roughnessFactor": 0.75
      },
      "extensions": {
        "KHR_materials_ior": {
          "ior": 1.45
        }
      }
    }
  ]
}
USD Preview Surface 
# USD Preview Surface — UsdShade.MaterialLook prim attributes
# Silicone Rubber (RTV) · finish: matte
def Material "mat_silicone" {
    token outputs:surface.connect = </mat_silicone/PreviewSurface.outputs:surface>

    def Shader "PreviewSurface" {
        uniform token info:id = "UsdPreviewSurface"
        color3f inputs:diffuseColor = (0.7454, 0.6867, 0.6308)
        float   inputs:metallic     = 0.000
        float   inputs:roughness    = 0.750
        float   inputs:ior          = 1.450
        float   inputs:opacity      = 1.000
        float   inputs:clearcoat    = 0.000
        token   outputs:surface
    }
}
↓ download glTF material
ProcessInjection Molding · Adhesive Bonding
Used inEyewear Frame · Prototype / Concept Model

Second life

repairabilitymoderate — silicone bonds to itself with silicone adhesive (Sil-Poxy, Smooth-On); inert and chemically stable.
recyclabilityvery low — silicones are essentially non-recyclable in mainstream streams; ground-silicone filler is a small specialty market.
disposal pathgeneral waste; biodegradation extremely slow.
typical longevity40 years (typical)
failure modes
  • UV degradation (slow; better than most polymers)
  • tear propagation from notches
  • oil / hydrocarbon-fuel attack on some silicone formulations

Dow Corning / Wacker silicone technical literature; ASTM D2000 elastomer classification.

Citations

  • datasheet · Smooth-On Mold Star 30 technical bulletin