HDPE GF20 vs HDPE GF40
Polymer · HDPE grade comparison
HDPE GF20 and HDPE GF40 are two grades of the same polymer grade, HDPE: GF20 (20% Glass Fiber) versus GF40 (40% Glass Fiber). The chemistry is identical, so every difference below comes from the condition. HDPE GF40 is the stronger of the two: yield strength 78 MPa (11.3 ksi) against 50 MPa (7.25 ksi) for HDPE GF20, about 56% more; tensile strength follows at 80 MPa (11.6 ksi) vs 55 MPa (7.98 ksi). In exchange, HDPE GF20 is the more ductile: elongation 3% versus 2% for HDPE GF40. HDPE GF20 is lighter (1.08 g/cm³ vs 1.26 g/cm³ for HDPE GF40) and HDPE GF40 is stiffer (7.8 GPa vs 4.2 GPa). On the shop floor, HDPE GF20 welds better (fair vs poor).
HDPE GF20Choose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
HDPE GF40Choose it when strength drives the design.
HDPE GF20 vs HDPE 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
Poisson's Ratio
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Flexural Strength
Flexural Modulus
Izod Impact, Notched
Hardness, Shore D
Hardness, Rockwell R
Same in both: Shear Modulus 0.4 GPa0.06 Msi · Bulk Modulus 3 GPa0.44 Msi · Compressive Modulus 0.9 GPa0.13 Msi · Shear Strength 20 MPa2.9 ksi · Fracture Toughness (K_IC) 2 MPa·√m1.8 ksi·√in
Physical
Density and transition temperatures.
Density
Water Absorption (24 h)
Water Absorption (Saturation)
Same in both: Melting Temperature (Tm) 132°C270 °F · Glass Transition (Tg) -110°C-166 °F · Refractive Index 1.54
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)
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Limiting Oxygen Index
Max Service Temperature (short-term)
Same in both: Min Service Temperature -50°C-58 °F · Vicat Softening Point (B50) 76°C169 °F
Electrical
Conductivity and insulation.
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Surface Resistivity
Same in both: Electrical Resistivity 1×10¹⁴ Ω·m3.94×10²¹ µΩ·in · Volume Resistivity 1×10¹⁵ Ω·cm · Comparative Tracking Index (CTI) 600 V
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: UV / Weathering Resistance 30 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Mold Shrinkage
Melt Flow Rate
Processing Melt Temperature (typ.)
Mold Temperature (typ.)
Same in both: Polishability 30 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Same in both: Embodied Water 90 L/kg10.8 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.
HDPE GF20 vs HDPE GF40 — frequently asked
Is HDPE GF40 stronger than HDPE GF20?
Yes. HDPE GF40 has a typical yield strength of 78 MPa (11.3 ksi) against 50 MPa (7.25 ksi) for HDPE GF20 — about 56% more. Tensile strength is 80 MPa (11.6 ksi) vs 55 MPa (7.98 ksi).
Which grade does FabDigit quote by default, GF20 or GF40?
Specify the condition in the material field or the drawing note; FabDigit prices the quote for the state you call out.
Which is easier to machine, HDPE GF20 or HDPE GF40?
HDPE GF20. Its machinability rates good (55/100) against fair (48/100) for HDPE GF40; for welding the order is HDPE GF20 first (fair, 40/100) then HDPE GF40 (poor, 30/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in HDPE GF20 and HDPE 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.