PEEK · grade · default condition
PEEK Unfilled
Properties of the Unfilled condition, compared with the other PEEK grades.
Pick for maximum toughness, elongation and electrical insulation, or when machining thin/complex parts from rod and plate.
What is PEEK Unfilled?
PEEK Unfilled is PEEK in the Unfilled grade — pick for maximum toughness, elongation and electrical insulation, or when machining thin/complex parts from rod and plate. PEEK Unfilled has a yield strength of 100 MPa (14.5 ksi) and a tensile strength of 100 MPa (14.5 ksi) — stronger than 95% of polymer grades. Elongation at break is 35% and the elastic modulus is 3.7 GPa (0.537 Msi). PEEK Unfilled has a density of 1.3 g/cm³ (0.047 lb/in³), heavier than 69% of polymer grades. Its glass-transition temperature is 143°C (289 °F).
Advantages
- High strength — 100 MPa (14.5 ksi), better than 95% of polymer grades
- High service temperature — 250°C (482 °F), better than 94% of polymer grades
- Stiff — 3.7 GPa (0.537 Msi), better than 83% of polymer grades
- Good corrosion resistance — 90/100, better than 81% of polymer grades
- Tough — resists crack growth — 3.5 MPa·√m (3.19 ksi·√in), better than 80% of polymer grades
Limitations
- High embodied carbon — 15 kg CO₂/kg, worse than 97% of polymer grades
PEEK Unfilled properties
Typical room-temperature values for PEEK Unfilled — 12 properties are specific to this condition; the rest are grade-level values shared by every PEEK grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical5
PEEK Unfilled has a density of 1.3 g/cm³ (0.047 lb/in³), heavier than 69% of polymer grades. Its glass-transition temperature is 143°C (289 °F).
Mechanical17
PEEK Unfilled has a yield strength of 100 MPa (14.5 ksi) and a tensile strength of 100 MPa (14.5 ksi) — stronger than 95% of polymer grades. Elongation at break is 35% and the elastic modulus is 3.7 GPa (0.537 Msi).
Thermal11
PEEK Unfilled is rated for continuous service to 250°C (482 °F). It conducts heat at 0.25 W/m·K (0.144 BTU/hr·ft·°F), better than 71% of polymer grades. Thermal expansion is 47 µm/m·K (26.1 µin/in·°F).
Electrical7
PEEK Unfilled is an electrical insulator with a dielectric strength of 21 kV/mm (533.4 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 81% of polymer grades. UV resistance is fair.
Sustainability4
Producing a kilogram of PEEK Unfilled takes about 290 MJ of energy and emits 15 kg of CO₂ — more than 95% of polymer grades. Typical recycled content is 0%.
Manufacturability8
PEEK Unfilled's machinability is very good (70/100, better than 73% of polymer grades); weldability fair (45/100); formability poor (30/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other PEEK grades and fills
PEEK is also supplied in 12 other conditions. The full side-by-side table is on the PEEK overview.
- VirginDefaultSpecify when full lot traceability and no reprocessed content are required (semiconductor, aerospace, medical).100 MPa tensile
- UnfilledDefaultPick for maximum toughness, elongation and electrical insulation, or when machining thin/complex parts from rod and plate.100 MPa tensile
- CF30Pick for highest strength/stiffness-to-weight, low CTE, better heat dissipation and static-dissipative behaviour.225 MPa yield · 107 HRM
- GF30Pick for high stiffness and creep resistance at 200–260 °C when electrical insulation must be retained.165 MPa yield · 105 HRM
- CF10Pick when moderate stiffness gain and dimensional stability are wanted while keeping some ductility and machinability.145 MPa tensile
- GF20PEEK compounded with 20% short glass fiber — higher stiffness, strength and creep resistance than unfilled PEEK with HDT near the melting point, at the cost of ductility and impact.140 MPa tensile
- Bearing GradePick for dry-running bushings, wear rings, seals and thrust washers needing low friction and low wear rate at high PV.125 MPa tensile
- ESDPick for semiconductor wafer handling, test sockets and fuel-system parts where charge build-up must be bled off.110 MPa tensile
- PTFE 10%Pick for low-friction sliding parts that must stay electrically insulating and reasonably tough (no fiber reinforcement).90 MPa tensile
- As PrintedUse for prototypes and low-load fixtures; expect anisotropy, partial crystallinity and Z-direction strength far below molded PEEK.85 MPa tensile
Working with PEEK Unfilled
Is PEEK easy to machine?
Machines cleanly with sharp carbide (polished flutes, positive rake) and air/flood cooling; glass- and carbon-filled grades are abrasive and want diamond-coated tooling, and thick machined parts should be annealed before finish cuts to avoid stress cracking.
Can PEEK be welded?
Joins by ultrasonic, laser, hot-plate, spin and infrared welding at 380–400 °C interface temperature; no solvent bonding — adhesive joints need plasma or abrasive surface activation.
Can PEEK be formed, bent or molded?
Inject at 360–400 °C melt with 170–200 °C mold for full crystallinity; resin must be dried (150 °C, 3 h), runners/gates generous, and slow crystallising thin sections may need post-mold annealing.
What surface finishes work on PEEK?
Can be machined-to-finish, bead-blasted, laser-marked or plasma treated for printing/metallising; not paintable without primer and not anodizable — parts are usually left natural tan or supplied in black.
PEEK chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| glass fiberGF variants only (chopped E-glass, sized for PAEK) | 10 – 40 | 30 |
| carbon fiberCF variants only (PAN-based chopped fiber) | 10 – 40 | 30 |
| PTFEbearing / lubricated variants | 5 – 15 | 10 |
| graphitebearing variants | 5 – 10 | 10 |
| carbon blackblack / ESD variants | 1 – 15 | 3 |
| poly(oxy-1,4-phenylene-oxy-1,4-phenyleneUnfilled grade; polymerised from 4,4'-difluorobenzophenone + hydroquinone in diphenyl sulfone | balance | — |
PEEK Unfilled — frequently asked
What is PEEK Unfilled used for?
PEEK Unfilled is typically used for spinal fusion implants, aerospace seals and back-up rings, downhole oil and gas seals, semiconductor wafer handling fixtures, bearings, bushings and wear pads and compressor valve plates. In short: ultra-performance plastic.
What is the yield strength of PEEK Unfilled?
PEEK Unfilled has a typical yield strength of 100 MPa (14.5 ksi) and a tensile strength of 100 MPa (14.5 ksi) — stronger than 95% of polymer grades. Strength varies by condition: see the 13 listed tempers.
Is PEEK Unfilled easy to machine?
Yes — machinability is rated very good (70/100, better than 73% of polymer grades). Machines cleanly with sharp carbide (polished flutes, positive rake) and air/flood cooling; glass- and carbon-filled grades are abrasive and want diamond-coated tooling, and thick machined parts should be annealed before finish cuts to avoid stress cracking.
Can PEEK Unfilled be welded?
With care — weldability is rated fair (45/100). Joins by ultrasonic, laser, hot-plate, spin and infrared welding at 380–400 °C interface temperature; no solvent bonding — adhesive joints need plasma or abrasive surface activation.
What surface finishes work on PEEK Unfilled?
Can be machined-to-finish, bead-blasted, laser-marked or plasma treated for printing/metallising; not paintable without primer and not anodizable — parts are usually left natural tan or supplied in black.
Can PEEK Unfilled be formed, bent or molded?
Inject at 360–400 °C melt with 170–200 °C mold for full crystallinity; resin must be dried (150 °C, 3 h), runners/gates generous, and slow crystallising thin sections may need post-mold annealing.
What is the maximum service temperature of PEEK Unfilled?
PEEK Unfilled is rated for continuous use to about 250°C (482 °F), and briefly to 300°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between PEEK Virgin and PEEK-CF30?
Virgin is the default condition — specify when full lot traceability and no reprocessed content are required (semiconductor, aerospace, medical). CF30: pick for highest strength/stiffness-to-weight, low CTE, better heat dissipation and static-dissipative behaviour. Yield strength is 100 MPa in Virgin versus 225 MPa in CF30.
Can FabDigit make parts in PEEK Unfilled?
Yes — PEEK Unfilled is available for CNC machining, sheet metal, injection molding and 3D printing with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- VICTREX PEEK 450G / 450GL30 / 450CA30 / 450FC30 product datasheets — Victrex plc (2023)
- KetaSpire PEEK design & processing guide — Solvay Specialty Polymers (2022)
- TECAPEEK stock shape property tables — Ensinger GmbH (2023)
- CAMPUS plastics multipoint data for PEEK grades — CWFG / CAMPUS (2024)
- ASM Engineered Materials Handbook: Engineering Plastics — ASM International (1988)
- ISO 527 / ISO 178 / ISO 75 / ISO 180 test methods; ASTM D638, D790, D648 — ISO / ASTM (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.