PEI vs POM
Polymer · grade comparison
PEI and POM are both polymer grades. PEI is the stronger of the two: yield strength 105 MPa (15.2 ksi) against 62 MPa (8.99 ksi) for POM, about 69% more; tensile strength follows at 105 MPa (15.2 ksi) vs 63 MPa (9.14 ksi). PEI is the more ductile: elongation 60% versus 30% for POM, and PEI is harder (87 Shore D vs 81 Shore D). PEI is lighter (1.27 g/cm³ vs 1.41 g/cm³ for POM) and PEI is stiffer (3.2 GPa vs 2.8 GPa). On the shop floor, POM machines more easily (excellent vs good) and POM sits in a lower cost tier (standard, $$) than PEI (specialty, $$$$$).
PEIChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
POMChoose it when the part is machined in volume, or when cost is the deciding factor.
PEI vs POM: 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
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Compressive Modulus
Flexural Strength
Flexural Modulus
Shear Strength
Fracture Toughness (K_IC)
Izod Impact, Notched
Hardness, Shore D
Hardness, Rockwell M
Hardness, Rockwell R
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Refractive Index
Light Transmission
Melting Temperature (Tm)
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
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Vicat Softening Point (B50)
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
Processing Melt Temperature (typ.)
Mold Temperature (typ.)
Same in both: Polishability 70 / 100 · Melt Flow Rate 9 g/10 min
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)
Modulus of Resilience
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 | PEI | POM |
|---|---|---|
| CNC machining | Yes | — |
| Sheet metal | Yes | — |
| 3D printing | Yes | — |
| Default condition | Unfilled (1000) | Unfilled |
| Relative cost | $$$$$ Specialty | $$ Standard |
| Min. machined wall | 0.5 mm | — |
| Best machined surface | Ra 0.8 µm | — |
| Conductive Coating | Yes | — |
| Dyeing (Nylon) | Yes | — |
| Painting | Yes | — |
| Primer Coating | Yes | — |
| Tinted Coating | Yes | — |
| Vacuum Metallization | Yes | — |
| Waterproof Coating | Yes | — |
Both are offered for Injection molding. They share 5 finishes: Chrome Plating (Plastic), EMI Shielding Coating, Soft Touch Coating, Spray Painting, UV Coating.
PEI vs POM — frequently asked
Is PEI stronger than POM?
Yes. PEI has a typical yield strength of 105 MPa (15.2 ksi) against 62 MPa (8.99 ksi) for POM — about 69% more. Tensile strength is 105 MPa (15.2 ksi) vs 63 MPa (9.14 ksi).
Which is cheaper, PEI or POM?
POM is the lower-cost material: it sits in the standard tier ($$) while PEI is specialty ($$$$$). 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, PEI or POM?
POM. Its machinability rates excellent (88/100) against good (65/100) for PEI; for welding the order is PEI first (good, 60/100) then POM (good, 55/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in PEI and POM 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.