PEEK (Polyether Ether Ketone)

Physical properties

Laser processing

Thermal decomposition of PEEK generates fumes of benzophenone, diphenyl ether, and other aromatic compounds at low concentration. Although less toxic than PVC or POM, ventilation is mandatory to avoid inhalation of pyrolysis products. Fumes have a faint phenolic odour.

CO₂: CO2 laser cutting possible on thin sheets (1–3mm) with high power. PEEK has a high melting point (~343°C) and requires significantly more energy than other thermoplastics. Engraving produces light marks on natural (beige) material or white marks on black PEEK. Edges can carbonise if power is not precisely calibrated. Use slow speed and high power for clean cuts.

Diode: Engraving possible on dark/natural PEEK at high power. Cutting is not practicable. The diode wavelength is poorly absorbed by unfilled PEEK.

Fiber: Fibre laser marking is optimal for PEEK: produces permanent high-contrast marks on natural or coloured surfaces. Common application in the medical industry for instrument marking and UDI (Unique Device Identification) codes.

CNC / milling processing

PEEK is the engineering thermoplastic with the best CNC milling characteristics: it produces sharp, clean chips without melting or chipping. Micrometric dimensional stability. Use sharp carbide bits, spindle speed 12,000–18,000 RPM, moderate feed. Does not require coolant, but a compressed air blast helps chip evacuation. Moderate tool wear.

3D printing

Post-processing

Sanding: PEEK can be dry-sanded thanks to its high melting point. Produces clean chips. Grits 180 → 400 → 800 → 1200 for semi-gloss finishes. Mirror polishing is possible with diamond compounds.

Primer: Direct painting is difficult due to low surface energy. This is not a common operation: PEEK is almost always used in its functional applications without aesthetic coating.

Gluing: Bondable with two-component structural epoxy adhesives after abrasion and degreasing with acetone. For high-temperature joints, thermal welding or mechanical joining with screws is preferred.

Seasoning: PEEK absorbs minimal moisture (~0.5% at saturation). For 3D printing filament, dry at 150°C for 3–4 hours before use. Store sealed with desiccant for critical applications.

Over time: PEEK is the thermoplastic with the best continuous thermal resistance (260°C continuous, peaks at 300°C). Immune to the vast majority of organic solvents, acids, and bases. Excellent resistance to ionising radiation. Does not degrade under UV. Hydrolysis resistance even in autoclave (repeatedly steam-sterilisable). Stability over time is virtually unlimited under standard service conditions.

Common defects

• Extremely difficult FDM 3D printing — requires hotend up to 400°C, heated bed at 120°C, heated enclosure at 60°C; warping is severe without these prerequisites
• Very high cost compared to other thermoplastics — always verify whether POM or Nylon PA6 can meet requirements before choosing PEEK
• Painting impractical without specific surface treatments

Safety

Recommended PPE: eye_protection

PEEK is one of the safest thermoplastics to process. In solid form it is inert and non-toxic. Mechanical processing (milling, turning) presents no particular risks beyond common plastic dust. Ventilation recommended for laser processing. Keep dry before 3D printing to avoid steam bubbles.

Availability and formats

Commercial formats: sheets 3–50mm, round and square bars, filament 1.75mm and 2.85mm for 3D printing, granules

Related materials

Sources

• ISO 10350 — Plastics acquisition and presentation of comparable single-point data (PEEK grade)
• Victrex PEEK 450G Technical Data Sheet
• ASTM D638 — Standard Test Method for Tensile Properties of Plastics