NBR vs Silicone
Polymer · grade comparison
NBR and Silicone are both polymer grades. NBR is the stronger of the two: tensile strength 16 MPa (2.32 ksi) against 8 MPa (1.16 ksi) for Silicone, about 100% more. In exchange, Silicone is the more ductile: elongation 500% versus 400% for NBR. Silicone is lighter (1.15 g/cm³ vs 1.25 g/cm³ for NBR) and NBR is stiffer (0.01 GPa vs 0 GPa). On the shop floor, NBR machines more easily (30 vs 20 out of 100), Silicone welds better (poor vs not recommended), and NBR sits in a lower cost tier (standard, $$) than Silicone (premium, $$$).
NBRChoose it when strength drives the design, or when the part is machined in volume.
SiliconeChoose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
NBR vs Silicone: 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.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Tensile Strength (Ultimate)
Elongation at Break
Shear Strength
Hardness, Shore A
Hardness, Shore D
Compression Set (22 h, 70 °C)
Shear Modulus
Bulk Modulus
Same in both: Poisson's Ratio 0.49 · Tear Strength 25 kN/m143 lbf/in
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Refractive Index
Light Transmission
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 Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Surface Resistivity
Comparative Tracking Index (CTI)
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.)
Polishability
Processing Melt Temperature (typ.)
Sustainability
Primary-production footprint per kilogram.
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Same in both: Embodied Energy (primary production) 110 MJ/kg47,292 BTU/lb
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Same in both: Specific Stiffness (E / density) 0 MN·m/kg · Thermal Diffusivity 0.1 mm²/s · Thermal Shock Resistance Index 3
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 | NBR | Silicone |
|---|---|---|
| Default condition | Solid | Medical Grade |
| Relative cost | $$ Standard | $$$ Premium |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both are offered for Injection molding. Both take the same 5 finishes: Chrome Plating (Plastic), EMI Shielding Coating, Soft Touch Coating, Spray Painting, UV Coating.
NBR vs Silicone — frequently asked
Is NBR stronger than Silicone?
Yes. NBR has a typical tensile strength of 16 MPa (2.32 ksi) against 8 MPa (1.16 ksi) for Silicone — about 100% more.
Which is cheaper, NBR or Silicone?
NBR is the lower-cost material: it sits in the standard tier ($$) while Silicone is premium ($$$). 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, NBR or Silicone?
NBR, by a small margin. Both rate poor for machinability — 30/100 against 20/100 for Silicone; for welding the order is Silicone first (poor, 20/100) then NBR (not recommended, 10/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in NBR and Silicone 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.