PEEK Plastic FAQ — Temperature, Machining, Cost & More

Common technical and purchasing questions about PEEK (polyether ether ketone), answered directly. If your question isn't here, the PEEK material overview covers the complete property and application picture.

At a glance:

• Maximum continuous service temperature: 480°F (250°C)
• PEEK handles thousands of autoclave cycles at 134°C with no degradation
• GF30 and CF30 grades are significantly stronger but less chemically resistant
• PEEK costs 10–15× more than Delrin; 20–40% more than Ultem
• ELS grade is for ESD control, not food or medical applications
• PEEK's Tg of 143°C does not represent a service limit for crystalline stock
• Standard carbide tooling machines PEEK well; PCD for high-volume CF30 work

Q1: What is PEEK's maximum service temperature?

PEEK supports continuous service at 480°F (250°C). Short-term excursions to 570°F (300°C) are tolerated. The crystalline melt temperature (Tm) is 343°C.

A common point of confusion is PEEK's Tg of 143°C (289°F). The Tg is where the amorphous polymer fraction softens — not the load-bearing limit for crystalline PEEK stock. Properly extruded rod and compression-molded sheet run at 30–35% crystallinity and retain useful stiffness well above the Tg, through the 250°C continuous-use rating.

For comparison: Ultem PEI is rated to 340°F (171°C) continuous, and acetal tops out at 185°F (85°C).

Q2: Can PEEK be autoclaved? How many cycles?

Yes. Testing at 134°C/273°F (prion-cycle conditions, 30 min, 30 psi) over 1,000 cycles shows no measurable change in tensile strength, flexural modulus, or dimensional stability for virgin PEEK and 450G.

PEEK is also compatible with 121°C gravity cycles, EtO, H₂O₂ plasma (STERRAD), peracetic acid, and dry heat. Gamma irradiation to 25 kGy causes minor yellowing with mechanical properties intact; 50 kGy should be verified for critical parts.

This autoclave stability is why PEEK is the default for reusable surgical instruments and trial implant bodies. See PEEK medical applications for details.

Q3: What's the difference between glass-filled (GF30) and unfilled virgin PEEK?

The primary differences are stiffness, strength, and ductility — in exchange for each other:

GF30 is stiffer and stronger, but becomes brittle — elongation drops from 30–50% to just 2–3%. For structural brackets and pump housings under sustained compressive load, GF30 is appropriate. For parts subject to shock loads, thin cross-sections, or chemical exposure, virgin PEEK's higher toughness and full chemical resistance usually wins.

GF30's lower CTE (~1.5 × 10⁻⁵ in/in/°F vs 2.6 for virgin) also matters in mixed-material assemblies — mismatch can cause stress at interfaces through thermal cycles. The full grade comparison is in the PEEK grades guide.

Q4: How much does PEEK cost, and why?

PEEK is a premium material. Indicative pricing (subject to market conditions):

• Virgin PEEK rod, 1.0" diameter: ~$180–$240 per foot
• Virgin PEEK sheet, 0.500" × 12" × 12": ~$250–$350 per sheet
• GF30 or CF30 grades: 15–50% premium over virgin in the same form

Cost drivers: PAEK resin production is concentrated among Victrex, Solvay, and Evonik; the polymerization process is energy-intensive; and total PEEK market volume remains small relative to commodity polymers. It competes on performance, not price.

Delrin at 1" rod diameter costs roughly $2–$5/ft; PEEK is 40–100× more expensive per pound. Ultem PEI runs 20–40% less than PEEK. PAI Torlon is comparable or slightly higher at small quantities.

The premium is justified when PEEK replaces a metal part (saving machining and weight), extends service life in aggressive chemistry, or satisfies a medical or food-contact certification requirement that cheaper materials can't meet.

Q5: Is PEEK better than Ultem for medical parts?

Both carry USP Class VI and FDA 21 CFR clearance. The deciding factors:

• Temperature/autoclave: PEEK handles 134°C prion-cycle autoclave; Ultem is preferred only for 121°C gravity-cycle instruments
• Chemical resistance: PEEK is broader — stronger against acids, steam, and repeated H₂O₂ exposure
• Transparency: Ultem natural is amber-transparent, useful for visual inspection of instrument bodies
• Cost: Ultem is 20–40% less. If the application only requires 121°C autoclave and mild chemical exposure, Ultem may be equivalent at lower cost

See the PEEK vs Ultem comparison for application-by-application detail.

Q6: What does PEEK ELS grade mean?

ELS (electrostatic) PEEK is formulated with a conductive additive to achieve surface resistivity in the static-dissipative range: 10⁶–10⁹ Ω/sq. This prevents charge accumulation without causing shorting in electrical applications.

Specify ELS for semiconductor wafer handling rings and end-effectors, cleanroom fixtures where triboelectric charging damages devices, and explosive-atmosphere tooling. ELS does not carry FDA or USP Class VI clearance — do not use it in food or medical applications.

Critical: black virgin PEEK contains carbon black for color only and is not ESD-dissipative. Specify PEEK ELS explicitly if static control is required.

Q7: Can PEEK be used in oil & gas downhole applications?

Yes. PEEK handles the combination of elevated temperature, high pressure, and aggressive chemistry found in downhole environments:

• H₂S (sour gas): resists hydrogen sulfide at downhole temperatures; nylon and acetal swell and degrade rapidly in H₂S-saturated brine
• CO₂-containing reservoirs: resistant at typical downhole pressures
• Steam injection: withstands short-term steam exposure beyond the 250°C continuous limit
• High pressure: compressive strength of 19,500 psi (virgin) to 31,000 psi (CF30) supports seal rings and bearings above 10,000 psi

Limit: high aromatic hydrocarbon concentrations at elevated temperature can cause minor swelling over extended exposure; verify with a fluid compatibility study. CF30 PEEK is preferred for sustained high-load bearing applications.

Q8: What carbide grade should I use to machine PEEK?

• Virgin PEEK: uncoated C-2/C-3 carbide, positive rake, polished chip breaker
• GF30: TiAlN-coated carbide; glass fiber dulls inserts 3–5× faster than virgin regardless of coating
• CF30: PCD inserts for production runs; TiAlN carbide for prototyping; dust collection required for carbon fiber dust

Full speeds, feeds, drilling, and tapping parameters are in the PEEK machining guide.

Q9: Does PEEK absorb moisture, and does it affect dimensions?

PEEK absorbs 0.10% moisture in 24-hour immersion and 0.50% at full saturation. Dimensional change at saturation is less than 0.05% — negligible for most precision applications. Nylon 6, by contrast, absorbs 9% at saturation with 1–2% dimensional change. PEEK parts need no moisture conditioning before machining and no dry storage. This stability is particularly valuable for semiconductor wet-etch fixtures operating in hot aqueous chemistry baths.

Q10: What sizes does PEEK rod come in, and what are the tolerances?

PEEK rod is stocked 0.25"–12.0" diameter in 4-ft and 6-ft lengths. OD tolerances as-extruded: ±0.010" (≤0.750"), ±0.015" (0.750–2.0"), ±0.020" (2.0–4.0"), ±0.030" (4.0–8.0"), ±0.040" (8.0–12.0"). Machine to final dimension for tighter tolerances — PEEK holds ±0.001–0.002" on CNC lathe. Sheet ranges 0.062"–4.0" thick in 12×12", 24×24", and 24×48" sizes. Full dimensional data: PEEK specifications.

More related guides

Cross-cluster suggestions to help shoppers and engineers explore adjacent topics:

Applications

• Bushings Bearings
• Gears
• Manifolds

Industries

• Aerospace
• Medical

Compare to other materials

• Peek Vs. Ultem Pei
• Peek Vs. Pai Torlon
• Peek Vs. Acetal Delrin

Frequently asked questions — Peek FAQ