E-51 vs EPN
Polymer · grade comparison
E-51 and EPN are both polymer grades. EPN is the stronger of the two: tensile strength 72 MPa (10.4 ksi) against 65 MPa (9.43 ksi) for E-51, about 11% more. In exchange, E-51 is the more ductile: elongation 4% versus 2% for EPN. E-51 is lighter (1.17 g/cm³ vs 1.21 g/cm³ for EPN) and EPN is stiffer (3.3 GPa vs 3 GPa). On the shop floor, E-51 sits in a lower cost tier (standard, $$) than EPN (premium, $$$).
E-51Choose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
EPNChoose it when strength drives the design, or when the part sees heat.
E-51 vs EPN: 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)
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
Physical
Density and transition temperatures.
Density
Glass Transition (Tg)
Refractive Index
Light Transmission
Same in both: Water Absorption (24 h) 0.15% · Water Absorption (Saturation) 1.6%
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
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
Limiting Oxygen Index
Max Service Temperature (short-term)
Same in both: Specific Heat Capacity 1,100 J/kg·K0.26 BTU/lb·°F
Electrical
Conductivity and insulation.
Dielectric Strength
Dielectric Constant (1 MHz)
Surface Resistivity
Same in both: Electrical Resistivity 1×10¹³ Ω·m3.94×10²⁰ µΩ·in · Dissipation Factor (1 MHz) 0.02 · Volume Resistivity 1×10¹⁵ Ω·cm · Comparative Tracking Index (CTI) 250 V
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.
Mold Shrinkage
Mold Temperature (typ.)
Processing Melt Temperature (typ.)
Same in both: Machinability 55 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Same in both: Embodied Water 250 L/kg30 gal/lb · Typical Recycled Content 0%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
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 | E-51 | EPN |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$ Standard | $$$ Premium |
| Min. machined wall | — | — |
| Best machined surface | — | — |
E-51 vs EPN — frequently asked
Is EPN stronger than E-51?
Yes. EPN has a typical tensile strength of 72 MPa (10.4 ksi) against 65 MPa (9.43 ksi) for E-51 — about 11% more.
Which is cheaper, E-51 or EPN?
E-51 is the lower-cost material: it sits in the standard tier ($$) while EPN is premium ($$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
When should I choose E-51 over EPN?
Pick E-51 when the part is bent, formed or impact-loaded, or when weight is the constraint. Pick EPN when strength drives the design, or when the part sees heat.
Ready to make it?
Upload a CAD file and FabDigit prices the part in E-51 and EPN 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.