Description

PEEK Sheet

PEEK (polyether ether ketone) is a high-performance, semi-crystalline engineering thermoplastic known for its exceptional balance of mechanical strength, thermal stability, chemical resistance, and electrical insulation. PEEK Natural refers to unfilled, unpigmented grades—typically beige/cream in color—chosen for purity, consistency, and precision machining. In sheet form, it is widely used for machined parts, insulators, wear plates, and precision spacers in demanding environments.

PEEK Sheet: Form, Processing Routes, and Sizes:

Manufacturing methods: Extruded sheet and compression-molded (pressed) sheet.

• Compression-molded: lower residual stress and better dimensional stability/flatness.
• Extruded: more economical; available in longer lengths.

Typical thickness and sizes: ~0.5 to 60 mm (and beyond); common formats include 500×1000 mm and 1000×2000 mm. Flatness and tolerances vary by producer and process.
Conditioning: Post-crystallization/annealing is often applied to stabilize crystallinity and reduce distortion during machining.

Key Properties of PEEK Natural (Unfilled):

Mechanical

• High tensile strength combined with useful ductility; tougher and more impact-resistant than fiber-reinforced grades.
• Stable modulus across a wide temperature range; very low creep and stress relaxation at service temperatures.
• High hardness and good wear resistance; suitable for loaded parts and moderate sliding duty.

Thermal

• Continuous use up to roughly 240–260°C (grade- and environment-dependent) with excellent dimensional stability.
• Tg ~143°C, Tm ~343°C; robust performance in hot water and saturated steam.
• Low coefficient of thermal expansion for a polymer; low thermal conductivity (good thermal insulator).

Chemical and Environmental

• Excellent resistance to hydrocarbons, oils, many acids and bases, and most industrial solvents.
• Outstanding hydrolysis and steam resistance; withstands repeated autoclave sterilization.
• Sensitivities: concentrated sulfuric acid (and some strong oxidizers) can attack PEEK. Natural grades show moderate UV stability; color darkening and some property change may occur outdoors—UV-stabilized black grades are preferred for long-term exposure.

Friction and Wear

• Inherently low coefficient of friction and good wear rates under lightly lubricated conditions.
• For high PV, high sliding speeds, or prolonged dry contact, tribological grades (e.g., PEEK with graphite/PTFE/carbon) are better suited.

Electrical

• Excellent electrical insulator with low dielectric constant and dissipation factor, stable over temperature and humidity.
• Natural PEEK is non-conductive (non-ESD). For ESD control, use carbon-filled or conductive grades.

Fire Safety and Emissions

• Generally self-extinguishing; many grades achieve UL 94 V-0 at common thicknesses (check specific grade).
• Low smoke and toxicity potential, supporting FST requirements in aerospace when specified.

Typical Properties and Technical Data of Unfilled PEEK (Polyetheretherketone):

• Density: ~1.30–1.32 g/cm³
• Tensile strength: ~90–100 MPa
• Tensile modulus: ~3.6–4.0 GPa
• Elongation at break: ~20–40%
• Compressive strength: ~110–120 MPa
• Hardness: Shore D ≈ 85 (Rockwell M ≈ 99)
• Glass transition (Tg): ≈ 143°C; Melting point (Tm): ≈ 343°C
• Continuous service temperature: up to ~240–260°C
• Linear CTE (23–100°C): ~47–55 ×10⁻⁶/K
• Thermal conductivity: ≈ 0.25 W/m·K
• Water absorption (24 h): ≈ 0.1% (saturation ≈ 0.5%)
• Dielectric constant (1 MHz): ≈ 3.2–3.5; Volume resistivity: >10¹⁵ Ω·cm; Dielectric strength: ≈ 20–25 kV/mm
• Dry coefficient of friction vs. steel: ≈ 0.3–0.4

Note: Actual values depend on resin grade, processing route, and supplier.

Key Applications for PEEK Natural Sheet:

• Aerospace and defense: thermal/electrical insulation plates, retainers, spacers, low-FST components (with approved grades).
• Automotive and transport: slipper/slide plates, wear pads, heat-resistant covers, engine-bay electrical insulation.
• Oil, gas, and chemical processing: valve seats and plates, gaskets, chemically resistant separators and insulators.
• Medical and laboratory: sterilization-resistant fixtures (autoclave, gamma), guides and spacers with chemical inertness.
• Semiconductor and electronics: process jigs/fixtures, wafer carriers and plates, high-voltage insulators with low ionic contamination.
• Food industry: contact components and guide/wear plates using FDA/EU-compliant natural grades.

Machining and Fabrication of PEEK Sheet:

• Tooling: sharp carbide tools with positive rake; light finishing by polishing or fine grinding for tight tolerances.
• Cutting parameters/cooling: moderate-to-high cutting speeds; air blast or light emulsion; avoid excessive heat buildup and warpage.
• Stress relief strategy: rough machine → anneal (e.g., 200–220°C, hold time per thickness, slow cool) → finish machine.
• Drilling/tapping: ensure effective chip evacuation; use larger thread profiles to accommodate CTE and potential creep.
• Bonding/joining: direct adhesive bonding is challenging; surface prep (sanding, plasma, primers) plus high-temperature epoxies improves results. Ultrasonic, laser, and resistance welding are feasible. Mechanical fastening is most robust at elevated temperatures.

PEEK Natural sheet delivers an exceptional combination of mechanical strength, thermal stability, chemical resistance, and electrical insulation in a machinable format. For applications demanding purity, dimensional stability, and durability in harsh thermal or chemical environments, unfilled PEEK is a dependable choice. For very high sliding loads or when maximum stiffness is required, consider tribological or fiber-reinforced grades.