CPET vs PET
Polymer · grade comparison
CPET and PET are both polymer grades. PET is the stronger of the two: yield strength 80 MPa (11.6 ksi) against 58 MPa (8.41 ksi) for CPET, about 38% more; tensile strength follows at 82 MPa (11.9 ksi) vs 62 MPa (8.99 ksi). In exchange, CPET is the more ductile: elongation 40% versus 20% for PET. PET is stiffer (3.1 GPa vs 2.8 GPa) and CPET runs hotter in service (115°C vs 100°C continuous). On the shop floor, PET machines more easily (very good vs good) and CPET welds better (good vs fair).
CPETChoose it when the part is bent, formed or impact-loaded, or when the part sees heat.
PETChoose it when strength drives the design, or when the part is machined in volume.
CPET 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)
Hardness, Rockwell R
Same in both: Poisson's Ratio 0.4 · Izod Impact, Notched 40 J/m0.75 ft·lbf/in · Hardness, Shore D 85 Shore D · Hardness, Rockwell M 94 HRM
Physical
Density and transition temperatures.
Density
Melting Temperature (Tm)
Glass Transition (Tg)
Water Absorption (24 h)
Light Transmission
Same in both: Water Absorption (Saturation) 0.5% · Refractive Index 1.575
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)
Min Service Temperature
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Vicat Softening Point (B50)
Max Service Temperature (short-term)
Same in both: Limiting Oxygen Index 22%
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Same in both: 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 | CPET | PET |
|---|---|---|
| CNC machining | — | Yes |
| Sheet metal | — | Yes |
| Injection molding | — | Yes |
| Default condition | — | Unfilled |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | — | 0.5 mm |
| Best machined surface | — | Ra 0.8 µm |
| Chrome Plating (Plastic) | — | Yes |
| EMI Shielding Coating | — | Yes |
| Painting | — | Yes |
| Soft Touch Coating | — | Yes |
| Spray Painting | — | Yes |
| UV Coating | — | Yes |
CPET vs PET — frequently asked
Is PET stronger than CPET?
Yes. PET has a typical yield strength of 80 MPa (11.6 ksi) against 58 MPa (8.41 ksi) for CPET — about 38% more. Tensile strength is 82 MPa (11.9 ksi) vs 62 MPa (8.99 ksi).
Which is cheaper, CPET 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, CPET or PET?
PET. Its machinability rates very good (78/100) against good (60/100) for CPET; for welding the order is CPET first (good, 65/100) then PET (fair, 45/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in CPET 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.