PEI vs RTPU
Polymer · grade comparison
PEI and RTPU are both polymer grades. PEI is the stronger of the two: yield strength 105 MPa (15.2 ksi) against 52 MPa (7.54 ksi) for RTPU, about 102% more; tensile strength follows at 105 MPa (15.2 ksi) vs 58 MPa (8.41 ksi). In exchange, RTPU is the more ductile: elongation 140% versus 60% for PEI, and PEI is harder (87 Shore D vs 78 Shore D). RTPU is lighter (1.2 g/cm³ vs 1.27 g/cm³ for PEI) and PEI is stiffer (3.2 GPa vs 2.1 GPa). On the shop floor, PEI machines more easily (65 vs 55 out of 100), RTPU welds better (very good vs good), and RTPU sits in a lower cost tier (premium, $$$) than PEI (specialty, $$$$$).
PEIChoose it when strength drives the design, or when the part sees heat.
RTPUChoose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
PEI vs RTPU: 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
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)
Polishability
Mold Shrinkage
Melt Flow Rate
Processing Melt Temperature (typ.)
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)
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 | RTPU |
|---|---|---|
| CNC machining | Yes | — |
| Sheet metal | Yes | — |
| Injection molding | Yes | — |
| 3D printing | Yes | — |
| Default condition | Unfilled (1000) | — |
| Relative cost | $$$$$ Specialty | $$$ Premium |
| Min. machined wall | 0.5 mm | — |
| Best machined surface | Ra 0.8 µm | — |
| Chrome Plating (Plastic) | Yes | — |
| Conductive Coating | Yes | — |
| Dyeing (Nylon) | Yes | — |
| EMI Shielding Coating | Yes | — |
| Painting | Yes | — |
| Primer Coating | Yes | — |
| Soft Touch Coating | Yes | — |
| Spray Painting | Yes | — |
| Tinted Coating | Yes | — |
| UV Coating | Yes | — |
| Vacuum Metallization | Yes | — |
| Waterproof Coating | Yes | — |
PEI vs RTPU — frequently asked
Is PEI stronger than RTPU?
Yes. PEI has a typical yield strength of 105 MPa (15.2 ksi) against 52 MPa (7.54 ksi) for RTPU — about 102% more. Tensile strength is 105 MPa (15.2 ksi) vs 58 MPa (8.41 ksi).
Which is cheaper, PEI or RTPU?
RTPU is the lower-cost material: it sits in the premium 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 RTPU?
PEI, by a small margin. Both rate good for machinability — 65/100 against 55/100 for RTPU; for welding the order is RTPU first (very good, 70/100) then PEI (good, 60/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in PEI and RTPU 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.