CPET vs PETG
Polymer · grade comparison
CPET and PETG are both polymer grades. CPET is the stronger of the two: yield strength 58 MPa (8.41 ksi) against 50 MPa (7.25 ksi) for PETG, about 16% more; tensile strength follows at 62 MPa (8.99 ksi) vs 50 MPa (7.25 ksi). In exchange, PETG is the more ductile: elongation 120% versus 40% for CPET, and CPET is harder (85 Shore D vs 78 Shore D). PETG is lighter (1.27 g/cm³ vs 1.38 g/cm³ for CPET) and CPET is stiffer (2.8 GPa vs 2.1 GPa). On the shop floor, PETG welds better (very good vs good) and PETG sits in a lower cost tier (budget, $) than CPET (standard, $$).
CPETChoose it when strength drives the design, or when the part sees heat.
PETGChoose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
CPET vs PETG: 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)
Refractive Index
Light Transmission
Same in both: Water Absorption (Saturation) 0.5%
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
Vicat Softening Point (B50)
Limiting Oxygen Index
Max Service Temperature (short-term)
Same in both: Specific Heat Capacity 1,200 J/kg·K0.29 BTU/lb·°F · Min Service Temperature -40°C-40 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Volume Resistivity
Surface Resistivity
Comparative Tracking Index (CTI)
Same in both: Dissipation Factor (1 MHz) 0.02
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 Carbon (primary production)
Embodied Water
Typical Recycled Content
Same in both: Embodied Energy (primary production) 84 MJ/kg36,114 BTU/lb
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Same in both: Thermal Diffusivity 0.1 mm²/s · 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 | CPET | PETG |
|---|---|---|
| CNC machining | — | Yes |
| Sheet metal | — | Yes |
| Injection molding | — | Yes |
| 3D printing | — | Yes |
| Default condition | — | Unfilled |
| Relative cost | $$ Standard | $ Budget |
| Min. machined wall | — | 0.5 mm |
| Best machined surface | — | Ra 0.8 µm |
| Chrome Plating (Plastic) | — | Yes |
| Conductive Coating | — | Yes |
| Dyeing (Nylon) | — | Yes |
| EMI Shielding Coating | — | Yes |
| Painting | — | Yes |
| Primer Coating | — | Yes |
| Soft Touch Coating | — | Yes |
| Spray Painting | — | Yes |
| Tinted Coating | — | Yes |
| UV Coating | — | Yes |
| Vacuum Metallization | — | Yes |
| Waterproof Coating | — | Yes |
CPET vs PETG — frequently asked
Is CPET stronger than PETG?
Yes. CPET has a typical yield strength of 58 MPa (8.41 ksi) against 50 MPa (7.25 ksi) for PETG — about 16% more. Tensile strength is 62 MPa (8.99 ksi) vs 50 MPa (7.25 ksi).
Which is cheaper, CPET or PETG?
PETG is the lower-cost material: it sits in the budget tier ($) while CPET is standard ($$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, CPET or PETG?
PETG, by a small margin. Both rate good for machinability — 65/100 against 60/100 for CPET; for welding the order is PETG first (very good, 80/100) then CPET (good, 65/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in CPET and PETG 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.