The highest-performing thermoplastic in routine use. PEEK combines continuous-use temperature of 260°C, chemical resistance approaching fluoropolymers, radiation tolerance for sterilization, and mechanical strength that lets it replace metal in specific applications. The reason it isn't used everywhere: raw stock costs $150–300/kg for virgin grade, and it chips like glass if machining parameters are wrong.
PEEK earns its high cost in applications where several performance attributes are simultaneously required: high continuous service temperature, dimensional stability under load, chemical inertness, biocompatibility, and machinability. No other thermoplastic combines all five. PTFE is more chemically resistant but has poor mechanical properties. PEI (Ultem) is cheaper and has similar chemistry but lower temperature ceiling. Metals handle higher temperatures but carry weight, conductivity, and biocompatibility trade-offs PEEK avoids.
The three killer applications for PEEK: (1) medical implants and surgical components where MRI transparency and bone-like modulus matter; (2) semiconductor processing equipment where chemical inertness and low outgassing in vacuum are required; (3) aerospace brackets and bushings where weight reduction over metal justifies the cost. Outside these, PEEK is often over-specified — ABS, Delrin, or PEI will handle most lower-requirement applications at 1/5 to 1/20 the cost.
PEEK stock prices (2026): virgin unfilled PEEK rod ~$200/kg, 30% glass-filled ~$150/kg, 30% carbon-filled ~$220/kg, medical-grade (Invibio PEEK-OPTIMA) ~$400–600/kg. The machined part cost is dominated by material cost, not labor, for any part over ~50g finished weight. Minimize stock size selection carefully — a 10% oversize in starting diameter can add more to part cost than the entire cutting operation.
| Grade | Filler | Key properties | Typical use |
|---|---|---|---|
| Virgin PEEK (unfilled) | None | Best ductility, transparent to RF, FDA-compliant grades available | Medical, food contact, electrical |
| PEEK GF30 | 30% glass fiber | Higher stiffness (9 GPa flex modulus), lower elongation, abrasive on tooling | Structural brackets, fluid handling |
| PEEK CF30 | 30% carbon fiber | Highest stiffness (15 GPa), electrical conductivity, lowest wear rate | Bushings, aerospace structure, tribological |
| PEEK-OPTIMA | Various (medical) | Invibio — ISO 10993 implant grade, validated biocompatibility | Spinal cages, trauma fixation, cranial implants |
| PEEK HT / PEEK-HT | High-temperature variant | Higher Tg (~165°C), extended continuous temp | Engine components, oil & gas downhole |
| PEEK + PTFE + graphite | Tribological blend | Self-lubricating, low friction coefficient | Seals, bearings, valve seats |
| Property | Value | Test method |
|---|---|---|
| Tensile strength at yield | 100 MPa | ISO 527 |
| Tensile modulus | 3.6 GPa | ISO 527 |
| Elongation at break | 30–50% | ISO 527 |
| Flexural strength | 165 MPa | ISO 178 |
| Flexural modulus | 3.8 GPa | ISO 178 |
| Compressive strength | 118 MPa | ISO 604 |
| Rockwell hardness | M99 / R126 | ISO 2039 |
| Glass transition (Tg) | 143°C | DSC |
| Melting point (Tm) | 343°C | DSC |
| HDT (1.8 MPa) | 152°C | ISO 75 |
| Continuous service temp | 260°C (intermittent to 300°C) | UL 746B |
| Density | 1.32 g/cm³ | ISO 1183 |
| Water absorption (24h) | 0.1% | ISO 62 |
| Dielectric strength | 23 kV/mm | IEC 60243-1 |
| Sterilizability | Autoclave (steam), gamma, E-beam, ETO — all tolerated | |
| Chemical resistance | Excellent to most acids, bases, hydrocarbons. Attacks: conc. H₂SO₄, fuming HNO₃ | |
PEEK machines beautifully if parameters are right, chips and cracks if wrong. The hazards: heat buildup (PEEK is semi-crystalline; local melting ruins parts), thermal stress warpage (residual stresses in extruded stock become visible after machining), and small-feature breakage (the material is stiff and relatively brittle). Sharp tools, positive rake, adequate coolant (water-soluble or compressed air — never oil-based for medical parts).
| Operation | Surface speed (m/min) | Feed per tooth (mm) | Notes |
|---|---|---|---|
| Face milling | 200–500 | 0.10–0.25 | Sharp carbide, positive rake, 2-flute |
| End milling (pocketing) | 150–300 | 0.05–0.15 | Down-milling, light chip loads |
| End milling (finish) | 200–400 | 0.03–0.08 | Single-flute, polished |
| Drilling | 50–100 | 0.10–0.25/rev | Peck cycle, relieve heat, parabolic flute |
| Tapping | 3–8 | — | Spiral-flute, form taps work well |
| Turning | 200–400 | 0.10–0.30/rev | Sharp insert, positive rake, chip breakers |
Glass-filled PEEK reduces tool life by ~70% vs. virgin. Use PCD inserts for production runs. Carbon-filled PEEK is similarly abrasive but also electrically conductive — impacts sensor-based part probing.
PEEK-OPTIMA per ISO 10993-1. Modulus similar to cortical bone, radiolucent for X-ray / CT imaging through implant.
Chucks, end-effectors, fluid manifolds. Chemical resistance to HF, NH₄OH, low outgassing in vacuum process.
Cabin interior structure, clamp blocks, fuel-system bushings. Replaces machined aluminum where weight matters.
Seals, backup rings, wear sleeves for 200°C+ well environments. Sour gas (H₂S) chemical resistance.
Connector bodies, coil formers, high-frequency applications where PTFE's ductility is inadequate.
Metering valves, piston seals, auger components. FDA 21 CFR 177.2415 compliant grades. Withstands CIP/SIP.
| Material | Max temp | Tensile str. | Cost ratio | When to prefer |
|---|---|---|---|---|
| PEEK (virgin) | 260°C | 100 MPa | 1.0× (baseline) | Reference |
| PEI (Ultem 1000) | 170°C | 85 MPa | 0.3× | Below 170°C + low budget |
| PPS (Ryton) | 220°C | 80 MPa | 0.25× | Chemical resistance, lower strength ok |
| PAI (Torlon) | 260°C | 185 MPa | 1.3× | Highest strength thermoplastic; harder to machine |
| PTFE | 260°C | 25 MPa | 0.3× | Chemical inertness, no mechanical load |
| Delrin (POM-H) | 90°C | 70 MPa | 0.08× | Ambient temp precision parts |
| Nylon 6/6 | 85°C | 85 MPa | 0.05× | General-purpose mechanical parts |
Injection-molded PEEK stock has different mechanical properties than machining-grade extruded or compression-molded rod/plate. Specify your supplier's grade and form. We source from Victrex, Solvay, or Ensinger — all with documented machining-grade forms.
Extruded PEEK stock retains internal stresses that release during machining, causing warpage on thin sections. Request pre-annealed stock (typically $30–50/kg premium) for precision parts. We can also anneal semi-finished parts between roughing and finishing operations.
PEEK is brittle enough at room temperature that small features can chip during handling, especially glass-filled grades. For medical parts, 1.5 mm minimum wall and 1.0 mm feature size are safer.
Don't prototype in standard PEEK and expect to transition to implant grade for production — the stock forms and supply chains are different. Invibio's PEEK-OPTIMA (the only FDA-cleared implant-grade PEEK) requires ~4-week lead time and full traceability chain. Build that into your project schedule.
We typically configure PEEK jobs to minimize material loss: nesting parts in plate stock, calculating starting-rod diameter carefully, and returning qualified scrap to the customer if requested. For parts over $500 material cost, this can save 15–25%.
Full mill certs, stress-relief annealing, cleanroom packaging on request. Specify Victrex / Solvay / Ensinger if you have a grade preference — we'll match it.