PBT vs PET
Polymer · grade comparison
PBT and PET are both polymer grades, both engineering plastic. PET is the stronger of the two: yield strength 80 MPa (11.6 ksi) against 55 MPa (7.98 ksi) for PBT, about 45% more; tensile strength follows at 82 MPa (11.9 ksi) vs 55 MPa (7.98 ksi). In exchange, PBT is the more ductile: elongation 100% versus 20% for PET. PBT is lighter (1.31 g/cm³ vs 1.39 g/cm³ for PET) and PET is stiffer (3.1 GPa vs 2.6 GPa). On the shop floor, PET machines more easily (very good vs good) and PBT welds better (very good vs fair).
PBTChoose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
PETChoose it when strength drives the design, or when the part is machined in volume.
PBT vs PET: 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
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
Same in both: Poisson's Ratio 0.4
Physical
Density and transition temperatures.
Density
Melting Temperature (Tm)
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.
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)
Same in both: Thermal Conductivity 0.25 W/m·K0.14 BTU/hr·ft·°F
Electrical
Conductivity and insulation.
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Same in both: Electrical Resistivity 1×10¹⁴ Ω·m3.94×10²¹ µΩ·in · 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).
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
Typical Recycled Content
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 | PBT | PET |
|---|---|---|
| CNC machining | — | Yes |
| Sheet metal | — | Yes |
| Default condition | Unfilled | Unfilled |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | — | 0.5 mm |
| Best machined surface | — | Ra 0.8 µm |
| Painting | — | Yes |
Both are offered for Injection molding. They share 5 finishes: Chrome Plating (Plastic), EMI Shielding Coating, Soft Touch Coating, Spray Painting, UV Coating.
PBT vs PET — frequently asked
Is PET stronger than PBT?
Yes. PET has a typical yield strength of 80 MPa (11.6 ksi) against 55 MPa (7.98 ksi) for PBT — about 45% more. Tensile strength is 82 MPa (11.9 ksi) vs 55 MPa (7.98 ksi).
Which is cheaper, PBT or PET?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, PBT or PET?
PET. Its machinability rates very good (78/100) against good (68/100) for PBT; for welding the order is PBT first (very good, 70/100) then PET (fair, 45/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in PBT and PET 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.