PEI GF20 vs PEI GF40
Polymer · PEI grade comparison
PEI GF20 and PEI GF40 are two grades of the same polymer grade, PEI: GF20 (20% glass fiber reinforced) versus GF40 (40% glass fiber reinforced). The chemistry is identical, so every difference below comes from the condition. PEI GF40 is the stronger of the two: tensile strength 190 MPa (27.6 ksi) against 145 MPa (21 ksi) for PEI GF20, about 31% more. In exchange, PEI GF20 is the more ductile: elongation 3.5% versus 2% for PEI GF40. PEI GF20 is lighter (1.42 g/cm³ vs 1.61 g/cm³ for PEI GF40) and PEI GF40 is stiffer (11.7 GPa vs 6.9 GPa). On the shop floor, PEI GF20 machines more easily (52 vs 38 out of 100).
PEI GF20Choose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
PEI GF40Choose it when strength drives the design.
PEI GF20 vs PEI GF40: 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
Tensile Strength (Ultimate)
Elongation at Break
Flexural Strength
Flexural Modulus
Izod Impact, Notched
Same in both: Shear Modulus 1.2 GPa0.17 Msi · Bulk Modulus 4 GPa0.55 Msi · Poisson's Ratio 0.36 · Yield Strength (0.2% offset) 105 MPa15.2 ksi · Compressive Strength 140 MPa20.3 ksi · Compressive Modulus 3 GPa0.44 Msi · Shear Strength 85 MPa12.3 ksi · Fracture Toughness (K_IC) 3 MPa·√m2.7 ksi·√in · Hardness, Shore D 87 Shore D · Hardness, Rockwell M 109 HRM · Hardness, Rockwell R 125 HRR
Physical
Density and transition temperatures.
Density
Same in both: Glass Transition (Tg) 217°C423 °F · Water Absorption (24 h) 0.25% · Water Absorption (Saturation) 1.25% · Refractive Index 1.66 · Light Transmission 78%
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Heat Deflection Temp. @ 1.8 MPa
Same in both: Specific Heat Capacity 1,100 J/kg·K0.26 BTU/lb·°F · Max Service Temperature (continuous) 170°C338 °F · Min Service Temperature -50°C-58 °F · Heat Deflection Temp. @ 0.45 MPa 210°C410 °F · Vicat Softening Point (B50) 219°C426 °F · Limiting Oxygen Index 47% · Max Service Temperature (short-term) 200°C392 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Resistivity 1×10¹⁵ Ω·m3.94×10²² µΩ·in · Dielectric Strength 33 kV/mm838 V/mil · Dielectric Constant (1 MHz) 3.15 · Dissipation Factor (1 MHz) 0.0013 · Volume Resistivity 1×10¹⁷ Ω·cm · Surface Resistivity 1×10¹⁶ Ω · Comparative Tracking Index (CTI) 175 V
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Corrosion Resistance 85 / 100 · UV / Weathering Resistance 40 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Mold Shrinkage
Same in both: Weldability 60 / 100 · Formability (cold) 45 / 100 · Polishability 70 / 100 · Melt Flow Rate 9 g/10 min · Processing Melt Temperature (typ.) 370°C698 °F · Mold Temperature (typ.) 150°C302 °F
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 230 MJ/kg98,882 BTU/lb · Embodied Carbon (primary production) 9 kg CO₂/kg · Embodied Water 400 L/kg47.9 gal/lb · Typical Recycled Content 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.
PEI GF20 vs PEI GF40 — frequently asked
Is PEI GF40 stronger than PEI GF20?
Yes. PEI GF40 has a typical tensile strength of 190 MPa (27.6 ksi) against 145 MPa (21 ksi) for PEI GF20 — about 31% more.
Which grade does FabDigit quote by default, GF20 or GF40?
Unfilled (1000) is the default PEI condition in the FabDigit quote flow (neither GF20 nor GF40). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, PEI GF20 or PEI GF40?
PEI GF20, by a small margin. Both rate fair for machinability — 52/100 against 38/100 for PEI GF40.
Ready to make it?
Upload a CAD file and FabDigit prices the part in PEI GF20 and PEI GF40 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.