Phenolic Foam vs Silicone Foam (Sponge Rubber)
Polymer · grade comparison
Phenolic Foam and Silicone Foam (Sponge Rubber) are both polymer grades. Silicone Foam (Sponge Rubber) is the stronger of the two: tensile strength 1 MPa (0.174 ksi) against 0.15 MPa (0.0218 ksi) for Phenolic Foam, about 8.0 times as much. Silicone Foam (Sponge Rubber) is the more ductile: elongation 160% versus 2% for Phenolic Foam. Phenolic Foam is lighter (0.05 g/cm³ vs 0.32 g/cm³ for Silicone Foam (Sponge Rubber)) and Phenolic Foam is stiffer (0.01 GPa vs 0 GPa). On the shop floor, Phenolic Foam machines more easily (excellent vs very good) and Phenolic Foam sits in a lower cost tier (standard, $$) than Silicone Foam (Sponge Rubber) (high, $$$$).
Phenolic FoamChoose it when weight is the constraint, or when the part is machined in volume.
Silicone Foam (Sponge Rubber)Choose it when strength drives the design, or when the part is bent, formed or impact-loaded.
Phenolic Foam vs Silicone Foam (Sponge Rubber): propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all polymer grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all polymer grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Phenolic FoamSilicone Foam (Sponge Rubber)
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Compressive Modulus
Flexural Strength
Flexural Modulus
Shear Strength
Hardness, Shore A
Tear Strength
Compression Set (22 h, 70 °C)
Physical
Density and transition temperatures.
Density
Water Absorption (24 h)
Water Absorption (Saturation)
Glass Transition (Tg)
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Limiting Oxygen Index
Max Service Temperature (short-term)
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Constant (1 MHz)
Dielectric Strength
Dissipation Factor (1 MHz)
Volume Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
UV / Weathering Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Mold Shrinkage
Mold Temperature (typ.)
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 0%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Same in both: Thermal Shock Resistance Index 0
Strength versus weight
Yield strength against density for every polymer grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Phenolic Foam | Silicone Foam (Sponge Rubber) |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$ Standard | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Phenolic Foam vs Silicone Foam (Sponge Rubber) — frequently asked
Is Silicone Foam (Sponge Rubber) stronger than Phenolic Foam?
Yes. Silicone Foam (Sponge Rubber) has a typical tensile strength of 1 MPa (0.174 ksi) against 0.15 MPa (0.0218 ksi) for Phenolic Foam — about 8.0 times as much.
Which is cheaper, Phenolic Foam or Silicone Foam (Sponge Rubber)?
Phenolic Foam is the lower-cost material: it sits in the standard tier ($$) while Silicone Foam (Sponge Rubber) is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, Phenolic Foam or Silicone Foam (Sponge Rubber)?
Phenolic Foam. Its machinability rates excellent (90/100) against very good (80/100) for Silicone Foam (Sponge Rubber).
Ready to make it?
Upload a CAD file and FabDigit prices the part in Phenolic Foam and Silicone Foam (Sponge Rubber) side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.