PEEK vs PEKK
Polymer · grade comparison
PEEK and PEKK are both polymer grades, both high performance plastic. PEEK is the stronger of the two: yield strength 100 MPa (14.5 ksi) against 95 MPa (13.8 ksi) for PEKK, about 5% more; tensile strength follows at 100 MPa (14.5 ksi) vs 95 MPa (13.8 ksi). PEEK is the more ductile: elongation 30% versus 8% for PEKK. PEKK is stiffer (3.9 GPa vs 3.7 GPa). On the shop floor, PEEK machines more easily (very good vs good) and PEKK welds better (good vs fair).
PEEKChoose it when strength drives the design, or when the part is bent, formed or impact-loaded.
PEKKChoose it when it will be welded.
PEEK vs PEKK: 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 Modulus
Flexural Strength
Flexural Modulus
Shear Strength
Izod Impact, Notched
Hardness, Rockwell M
Hardness, Rockwell R
Same in both: Poisson's Ratio 0.4 · Compressive Strength 130 MPa18.9 ksi · Fracture Toughness (K_IC) 3.5 MPa·√m3.2 ksi·√in · Hardness, Shore D 86 Shore D
Physical
Density and transition temperatures.
Melting Temperature (Tm)
Glass Transition (Tg)
Water Absorption (24 h)
Water Absorption (Saturation)
Same in both: Density 1.3 g/cm³0.05 lb/in³
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)
Heat Deflection Temp. @ 0.45 MPa
Heat Deflection Temp. @ 1.8 MPa
Vicat Softening Point (B50)
Limiting Oxygen Index
Same in both: Min Service Temperature -60°C-76 °F · Max Service Temperature (short-term) 300°C572 °F
Electrical
Conductivity and insulation.
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Comparative Tracking Index (CTI)
Same in both: Electrical Resistivity 1×10¹⁴ Ω·m3.94×10²¹ µΩ·in · Volume Resistivity 1×10¹⁶ Ω·cm · Surface Resistivity 1×10¹⁵ Ω
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Same in both: UV / Weathering Resistance 45 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Weldability
Formability (cold)
Polishability
Melt Flow Rate
Mold Temperature (typ.)
Same in both: Mold Shrinkage 1.2% · Processing Melt Temperature (typ.) 380°C716 °F
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 0%
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 | PEEK | PEKK |
|---|---|---|
| CNC machining | Yes | — |
| Sheet metal | Yes | — |
| Injection molding | Yes | — |
| Default condition | Virgin | Unfilled |
| Relative cost | $$$$$ Specialty | $$$$$ Specialty |
| Min. machined wall | 0.8 mm | — |
| Best machined surface | Ra 0.8 µm | — |
| Chrome Plating (Plastic) | Yes | — |
| Spray Painting | Yes | — |
Both are offered for 3D printing. They share 10 finishes: Conductive Coating, Dyeing (Nylon), EMI Shielding Coating, Painting, Primer Coating, Soft Touch Coating, Tinted Coating, UV Coating, Vacuum Metallization, Waterproof Coating.
PEEK vs PEKK — frequently asked
Is PEEK stronger than PEKK?
Yes. PEEK has a typical yield strength of 100 MPa (14.5 ksi) against 95 MPa (13.8 ksi) for PEKK — about 5% more. Tensile strength is 100 MPa (14.5 ksi) vs 95 MPa (13.8 ksi).
Which is cheaper, PEEK or PEKK?
Both sit in the same relative cost tier ($$$$$, specialty); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, PEEK or PEKK?
PEEK. Its machinability rates very good (70/100) against good (60/100) for PEKK; for welding the order is PEKK first (good, 55/100) then PEEK (fair, 45/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in PEEK and PEKK 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.