CPET BLK vs CPET GF30
Polymer · CPET grade comparison
CPET BLK and CPET GF30 are two grades of the same polymer grade, CPET: BLK (carbon-black / pigmented CPET tray sheet) versus GF30 (30% glass-fiber reinforced crystalline PET). The chemistry is identical, so every difference below comes from the condition. CPET GF30 is the stronger of the two: tensile strength 150 MPa (21.8 ksi) against 60 MPa (8.7 ksi) for CPET BLK, about 150% more. In exchange, CPET BLK is the more ductile: elongation 30% versus 2.5% for CPET GF30. CPET BLK is lighter (1.38 g/cm³ vs 1.56 g/cm³ for CPET GF30) and CPET GF30 is stiffer (9.5 GPa vs 2.8 GPa). On the shop floor, CPET BLK machines more easily (good vs fair) and CPET GF30 welds better (good vs poor).
CPET BLKChoose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
CPET GF30Choose it when strength drives the design, or when the part sees heat.
CPET BLK vs CPET GF30: 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)
Yield Strength (0.2% offset)
Elongation at Break
Compressive Strength
Flexural Strength
Flexural Modulus
Shear Strength
Fracture Toughness (K_IC)
Izod Impact, Notched
Hardness, Rockwell M
Hardness, Rockwell R
Same in both: Shear Modulus 1 GPa0.15 Msi · Bulk Modulus 4 GPa0.64 Msi · Poisson's Ratio 0.4 · Compressive Modulus 2.8 GPa0.41 Msi · Hardness, Shore D 85 Shore D
Physical
Density and transition temperatures.
Density
Same in both: Melting Temperature (Tm) 250°C482 °F · Glass Transition (Tg) 78°C172 °F · Water Absorption (24 h) 0.1% · Water Absorption (Saturation) 0.5% · Refractive Index 1.575
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
Limiting Oxygen Index
Same in both: Specific Heat Capacity 1,200 J/kg·K0.29 BTU/lb·°F · Min Service Temperature -40°C-40 °F · Vicat Softening Point (B50) 190°C374 °F · Max Service Temperature (short-term) 220°C428 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Same in both: Dielectric Strength 20 kV/mm508 V/mil · Dielectric Constant (1 MHz) 3.3 · Dissipation Factor (1 MHz) 0.02 · Volume Resistivity 1×10¹⁵ 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)
Mold Shrinkage
Melt Flow Rate
Same in both: Polishability 45 / 100 · Processing Melt Temperature (typ.) 278°C532 °F · Mold Temperature (typ.) 140°C284 °F
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 84 MJ/kg36,114 BTU/lb · Embodied Carbon (primary production) 3 kg CO₂/kg · Embodied Water 80 L/kg9.6 gal/lb · Typical Recycled Content 40%
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.
CPET BLK vs CPET GF30 — frequently asked
Is CPET GF30 stronger than CPET BLK?
Yes. CPET GF30 has a typical tensile strength of 150 MPa (21.8 ksi) against 60 MPa (8.7 ksi) for CPET BLK — about 150% more.
Which grade does FabDigit quote by default, BLK or GF30?
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, CPET BLK or CPET GF30?
CPET BLK. Its machinability rates good (58/100) against fair (45/100) for CPET GF30; for welding the order is CPET GF30 first (good, 65/100) then CPET BLK (poor, 25/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in CPET BLK and CPET GF30 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.