EPDM vs IIR
Polymer · grade comparison
EPDM and IIR are both polymer grades. IIR is the more ductile: elongation 600% versus 400% for EPDM. EPDM is stiffer (0.01 GPa vs 0.01 GPa) and EPDM conducts heat better (0.3 W/m·K vs 0.13 W/m·K). On the shop floor, EPDM welds better (poor vs not recommended).
EPDMChoose it when it will be welded.
IIRChoose it when the part is bent, formed or impact-loaded.
EPDM vs IIR: 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
Bulk Modulus
Poisson's Ratio
Elongation at Break
Hardness, Shore A
Hardness, Shore D
Tear Strength
Compression Set (22 h, 70 °C)
Same in both: Tensile Strength (Ultimate) 12 MPa1.7 ksi
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Same in both: Water Absorption (24 h) 0.5%
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Max Service Temperature (continuous)
Limiting Oxygen Index
Max Service Temperature (short-term)
Same in both: Thermal Expansion (CTE, 20–100 °C) 180 µm/m·K100 µin/in·°F · Min Service Temperature -50°C-58 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Comparative Tracking Index (CTI)
Same in both: Dielectric Strength 25 kV/mm635 V/mil
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.
Weldability
Formability (cold)
Polishability
Processing Melt Temperature (typ.)
Same in both: Machinability 30 / 100 · Mold Shrinkage 2.5% · Mold Temperature (typ.) 175°C347 °F
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Water
Same in both: Embodied Carbon (primary production) 4 kg CO₂/kg · Typical Recycled Content 5%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Thermal Shock Resistance Index
Same in both: 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 | EPDM | IIR |
|---|---|---|
| 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 | — |
EPDM vs IIR — frequently asked
What is the difference between EPDM and IIR?
EPDM and IIR are both polymer grades. IIR is the more ductile: elongation 600% versus 400% for EPDM. EPDM is stiffer (0.01 GPa vs 0.01 GPa) and EPDM conducts heat better (0.3 W/m·K vs 0.13 W/m·K).
Which is cheaper, EPDM or IIR?
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.
Which welds better, EPDM or IIR?
EPDM. Its weldability rates poor (15/100) against not recommended (5/100) for IIR.
Ready to make it?
Upload a CAD file and FabDigit prices the part in EPDM and IIR 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.