PBT GF15 vs PBT GF40
Polymer · PBT grade comparison
PBT GF15 and PBT GF40 are two grades of the same polymer grade, PBT: GF15 (15% short glass fiber reinforced) versus GF40 (40% short glass fiber reinforced). The chemistry is identical, so every difference below comes from the condition. PBT GF40 is the stronger of the two: tensile strength 155 MPa (22.5 ksi) against 95 MPa (13.8 ksi) for PBT GF15, about 63% more. In exchange, PBT GF15 is the more ductile: elongation 3.5% versus 2.3% for PBT GF40. PBT GF15 is lighter (1.42 g/cm³ vs 1.63 g/cm³ for PBT GF40) and PBT GF40 is stiffer (13 GPa vs 5.6 GPa). On the shop floor, PBT GF15 machines more easily (good vs poor).
PBT GF15Choose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
PBT GF40Choose it when strength drives the design, or when the part sees heat.
PBT GF15 vs PBT 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
Hardness, Rockwell M
Same in both: Shear Modulus 0.93 GPa0.13 Msi · Bulk Modulus 4 GPa0.61 Msi · Poisson's Ratio 0.4 · Yield Strength (0.2% offset) 55 MPa8 ksi · Compressive Strength 85 MPa12.3 ksi · Compressive Modulus 2.4 GPa0.35 Msi · Shear Strength 45 MPa6.5 ksi · Fracture Toughness (K_IC) 2.5 MPa·√m2.3 ksi·√in · Hardness, Shore D 82 Shore D · Hardness, Rockwell R 118 HRR
Physical
Density and transition temperatures.
Density
Same in both: Melting Temperature (Tm) 225°C437 °F · Glass Transition (Tg) 55°C131 °F · Water Absorption (24 h) 0.09% · Water Absorption (Saturation) 0.45%
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Same in both: Specific Heat Capacity 1,500 J/kg·K0.36 BTU/lb·°F · Min Service Temperature -40°C-40 °F · Vicat Softening Point (B50) 178°C352 °F · Limiting Oxygen Index 21% · Max Service Temperature (short-term) 160°C320 °F
Electrical
Conductivity and insulation.
Same in both: Electrical Resistivity 1×10¹⁴ Ω·m3.94×10²¹ µΩ·in · Dielectric Strength 23 kV/mm584 V/mil · Dielectric Constant (1 MHz) 3.1 · Dissipation Factor (1 MHz) 0.02 · Volume Resistivity 1×10¹⁶ Ω·cm · Surface Resistivity 1×10¹⁵ Ω · Comparative Tracking Index (CTI) 600 V
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Corrosion Resistance 82 / 100 · UV / Weathering Resistance 35 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Mold Shrinkage
Same in both: Weldability 70 / 100 · Formability (cold) 20 / 100 · Polishability 55 / 100 · Melt Flow Rate 25 g/10 min · Processing Melt Temperature (typ.) 250°C482 °F · Mold Temperature (typ.) 70°C158 °F
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 105 MJ/kg45,142 BTU/lb · Embodied Carbon (primary production) 5 kg CO₂/kg · Embodied Water 250 L/kg30 gal/lb · Typical Recycled Content 5%
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.
PBT GF15 vs PBT GF40 — frequently asked
Is PBT GF40 stronger than PBT GF15?
Yes. PBT GF40 has a typical tensile strength of 155 MPa (22.5 ksi) against 95 MPa (13.8 ksi) for PBT GF15 — about 63% more.
Which grade does FabDigit quote by default, GF15 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, PBT GF15 or PBT GF40?
PBT GF15. Its machinability rates good (55/100) against poor (33/100) for PBT GF40.
Ready to make it?
Upload a CAD file and FabDigit prices the part in PBT GF15 and PBT 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.