PEEK · reinforced grade
PEEK-GF20
Properties of the GF20 condition, compared with the other PEEK grades.
PEEK 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.
What is PEEK-GF20?
PEEK-GF20 is PEEK in the GF20 grade — pEEK 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. PEEK-GF20 has a yield strength of 100 MPa (14.5 ksi) and a tensile strength of 140 MPa (20.3 ksi) — stronger than 95% of polymer grades. Elongation at break is 3% and the elastic modulus is 7.5 GPa (1.09 Msi). PEEK-GF20 has a density of 1.44 g/cm³ (0.052 lb/in³), heavier than 84% of polymer grades. Its glass-transition temperature is 143°C (289 °F). Virgin is the default condition FabDigit quotes; GF20 is available on request or by drawing note.
Advantages
- High service temperature — 260°C (500 °F), better than 97% of polymer grades
- High strength — 100 MPa (14.5 ksi), better than 95% of polymer grades
- Stiff — 7.5 GPa (1.09 Msi), better than 90% of polymer grades
- Conducts heat well — 0.34 W/m·K (0.196 BTU/hr·ft·°F), better than 89% of polymer grades
- Good corrosion resistance — 90/100, better than 81% of polymer grades
Limitations
- High embodied carbon — 15 kg CO₂/kg, worse than 97% of polymer grades
- Heavy — 1.44 g/cm³ (0.052 lb/in³), worse than 84% of polymer grades
- Limited ductility — 3%, worse than 83% of polymer grades
- Limited formability — 15/100, worse than 80% of polymer grades
PEEK-GF20 properties
Typical room-temperature values for PEEK-GF20 — 44 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-GF20 has a density of 1.44 g/cm³ (0.052 lb/in³), heavier than 84% of polymer grades. Its glass-transition temperature is 143°C (289 °F).
Mechanical17
PEEK-GF20 has a yield strength of 100 MPa (14.5 ksi) and a tensile strength of 140 MPa (20.3 ksi) — stronger than 95% of polymer grades. Elongation at break is 3% and the elastic modulus is 7.5 GPa (1.09 Msi).
Thermal11
PEEK-GF20 is rated for continuous service to 260°C (500 °F). It conducts heat at 0.34 W/m·K (0.196 BTU/hr·ft·°F), better than 89% of polymer grades. Thermal expansion is 25 µm/m·K (13.9 µin/in·°F).
Electrical7
PEEK-GF20 is an electrical insulator with a dielectric strength of 20 kV/mm (508 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 good.
Sustainability4
Producing a kilogram of PEEK-GF20 takes about 270 MJ of energy and emits 15 kg of CO₂ — more than 94% of polymer grades. Typical recycled content is 0%.
Manufacturability8
PEEK-GF20's machinability is good (55/100, worse than 63% of polymer grades); weldability poor (30/100); formability poor (15/100).
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-GF20
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-GF20 — frequently asked
What is PEEK-GF20 used for?
PEEK-GF20 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-GF20?
PEEK-GF20 has a typical yield strength of 100 MPa (14.5 ksi) and a tensile strength of 140 MPa (20.3 ksi) — stronger than 95% of polymer grades. Strength varies by condition: see the 13 listed tempers.
Is PEEK-GF20 easy to machine?
Reasonably — machinability is rated good (55/100, worse than 63% 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-GF20 be welded?
Not readily — weldability is rated poor (30/100). 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-GF20?
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-GF20 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-GF20?
PEEK-GF20 is rated for continuous use to about 260°C (500 °F), and briefly to 310°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-GF20?
Yes — PEEK-GF20 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.