CIIR vs EPDM
Polymer · grade comparison
CIIR and EPDM are both polymer grades. CIIR is the more ductile: elongation 500% versus 400% for EPDM, and EPDM is harder (22 Shore D vs 15 Shore D). EPDM is stiffer (0.01 GPa vs 0 GPa) and CIIR runs hotter in service (140°C vs 120°C continuous).
CIIRChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
CIIR vs EPDM: 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
Shear Modulus
Elongation at Break
Shear Strength
Hardness, Shore A
Hardness, Shore D
Tear Strength
Compression Set (22 h, 70 °C)
Same in both: Bulk Modulus 2 GPa0.29 Msi · Poisson's Ratio 0.5 · Tensile Strength (Ultimate) 12 MPa1.7 ksi
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
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.
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Comparative Tracking Index (CTI)
Same in both: Electrical Resistivity 1×10¹² Ω·m3.94×10¹⁹ µΩ·in · Volume Resistivity 1×10¹⁴ Ω·cm
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.
Formability (cold)
Mold Shrinkage
Processing Melt Temperature (typ.)
Weldability
Polishability
Same in both: Machinability 30 / 100 · Mold Temperature (typ.) 175°C347 °F
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 5%
Common Calculations
Ratios derived from the values above.
Thermal Shock Resistance Index
Same in both: Specific Strength (UTS / density) 10 kN·m/kg · Specific Stiffness (E / density) 0 MN·m/kg · Thermal Diffusivity 0.1 mm²/s
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 | CIIR | EPDM |
|---|---|---|
| Injection molding | — | Yes |
| Default condition | — | Solid |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | — | — |
| Best machined surface | — | — |
| Chrome Plating (Plastic) | — | Yes |
| EMI Shielding Coating | — | Yes |
| Soft Touch Coating | — | Yes |
| Spray Painting | — | Yes |
| UV Coating | — | Yes |
CIIR vs EPDM — frequently asked
What is the difference between CIIR and EPDM?
CIIR and EPDM are both polymer grades. CIIR is the more ductile: elongation 500% versus 400% for EPDM, and EPDM is harder (22 Shore D vs 15 Shore D). EPDM is stiffer (0.01 GPa vs 0 GPa) and CIIR runs hotter in service (140°C vs 120°C continuous).
Which is cheaper, CIIR or EPDM?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
When should I choose CIIR over EPDM?
Pick CIIR when the part is bent, formed or impact-loaded, or when the part sees heat.
Ready to make it?
Upload a CAD file and FabDigit prices the part in CIIR and EPDM 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.