The Complete PEEK Grade Selection Guide: Virgin, Filled, and Specialty Grades

The Cost of Getting the Grade Wrong

PEEK has earned its reputation as the “king of engineering polymers” — but PEEK isn’t a single material. Virgin resin, carbon-fiber-reinforced, glass-fiber-reinforced, wear-grade bearing compound… across these grades, tensile strength can vary by over 50%, and friction coefficient can vary by a factor of 10.

A wrong selection won’t just underperform: it can mean shortened service life, unplanned equipment downtime, or structural failure with serious liability implications. For industries like precision machinery, medical devices, and semiconductor equipment, the cost of a material mismatch routinely exceeds the cost difference between grades.

This guide walks through the core characteristics of each mainstream PEEK grade and when to use them.

PEEK Family Overview

Grade	Common Name	Key Trait	Typical Use
Virgin PEEK	Unfilled	Balanced properties; food/medical compatible	Medical devices, food equipment, electrical insulation
PEEK CF30	Carbon-filled 30%	Highest strength-to-weight; low friction	Aerospace structures, precision machinery, high-load parts
PEEK GF30	Glass-filled 30%	High stiffness; cost-effective; electrically insulating	Pumps, valves, structural brackets
PEEK FC30	Bearing grade	Ultra-low friction; self-lubricating	Bearings, gears, sliding guides
PEEK PTFE	PTFE-modified	Lowest friction; chemical inertness	Seals, pistons, corrosive-environment bearings
Medical PEEK	Medical grade	Full biocompatibility certification; radiolucent	Orthopedic implants, dental restorations

Virgin PEEK: The Versatile Baseline

Core Properties

Tensile strength: ~100 MPa
Flexural modulus: ~4.1 GPa
Continuous service temperature: 260°C
Coefficient of friction: 0.35–0.45 (dry)
Density: 1.30 g/cm³

Virgin PEEK is the cleanest form — no fillers, no modifiers. It retains full natural biocompatibility and chemical inertness. It resists virtually all organic solvents and most strong acids and bases, and delivers excellent electrical properties (volume resistivity up to 10¹⁶ Ω·cm).

Best Fit Applications

✅ Medical devices and implants Virgin PEEK meets ISO 10993 biocompatibility requirements and is radiolucent — it doesn’t artifact in CT or MRI imaging. It’s a key alternative to UHMWPE and titanium in spinal cages, bone fixation plates, and similar implants.

✅ Food and pharmaceutical processing equipment Virgin PEEK is FDA-compliant for food contact. It withstands steam autoclave sterilization and CIP (clean-in-place) cleaning cycles without leaching anything into the process stream.

✅ High-frequency electrical insulation With a low dielectric constant (3.2 at 10 GHz) and low dissipation factor (0.003), Virgin PEEK is a natural choice for insulating components in 5G base stations, radar, and microwave communication systems.

⚠️ Not ideal for: High-load sliding/friction applications (friction coefficient is higher than wear grades), or applications where maximum stiffness is required.

PEEK CF30: The Performance Flagship

Core Properties

Tensile strength: ~200 MPa (+100% vs. virgin)
Flexural modulus: ~18 GPa (+340% vs. virgin)
HDT at 1.82 MPa: >315°C
Coefficient of friction: 0.10–0.15 (dry)
Density: 1.41 g/cm³
Thermal conductivity: ~1.0 W/m·K (2× virgin)

Adding 30% carbon fiber fundamentally reshapes the PEEK property profile. CF30 delivers the highest specific stiffness (stiffness-to-weight ratio) in the PEEK family, alongside lower friction and better wear resistance than virgin grade.

Best Fit Applications

✅ Aerospace and lightweight structures In brackets, guides, connectors, and fittings that need both high strength and low weight, PEEK CF30 can directly replace aluminum alloy with weight savings of 30% or more.

✅ Precision machinery and robot joints High flexural modulus means minimal elastic deflection — critical in robotic arm joints, lead screw nuts, and precision drive components where positioning accuracy matters.

✅ High-speed or high-temperature friction pairs Under dry or starved-lubrication conditions, CF30’s low friction significantly reduces heat buildup, extending component life in high-speed bearings and compressor components.

⚠️ Watch out for:

CF30 is electrically conductive (carbon fiber conducts electricity) — don’t use it where electrical isolation is required
Carbon fibers create anisotropy; factor fiber orientation into load path design
Highly abrasive to cutting tools — carbide or PCD tooling required

PEEK GF30: Stiffness with Insulation, at Better Cost

Core Properties

Tensile strength: ~160 MPa
Flexural modulus: ~10 GPa
HDT at 1.82 MPa: >305°C
Coefficient of friction: 0.40–0.50 (dry — slightly higher than virgin)
Density: 1.51 g/cm³
Electrical insulation: retained (glass fibers don’t conduct)

GF30 improves stiffness and dimensional stability over virgin PEEK, while maintaining electrical insulation — the key advantage over CF30. Flexural modulus is roughly half that of CF30, but the price difference is meaningful, and the electrically insulating property opens up applications CF30 can’t serve.

Best Fit Applications

✅ Pump bodies, valves, and pipe fittings GF30 handles the combination of chemical resistance, dimensional stability under pressure, and elevated temperature that these components demand.

✅ Electrical and electronic insulating structures Connector housings, coil formers, and other parts that need high stiffness without sacrificing electrical isolation — GF30 is the natural upgrade from virgin PEEK.

✅ Injection-molded structural components GF30’s better isotropy (compared to CF30) makes dimensional behavior more predictable in complex injection-molded geometries.

⚠️ Not recommended for: High-speed sliding applications — GF30’s dry friction coefficient is high enough to cause accelerated wear of the mating surface.

PEEK FC30 (Bearing Grade): The Tribology Specialist

Typical Formulation

Bearing-grade PEEK uses compound filler systems. The most common:

CF/PTFE/graphite ternary composite (e.g., CF15 + PTFE10 + graphite 5%)
CF30 + graphite (FC30)

Core Properties (FC30)

Tensile strength: ~140 MPa
Coefficient of friction: 0.05–0.10 (extremely low, approaching PTFE)
PV limit: 10× higher than virgin PEEK
Linear wear rate: extremely low under demanding dynamic contact

The synergy in the ternary composite is deliberate: carbon fiber raises strength and load capacity, PTFE reduces friction, and graphite solid lubricant provides additional boundary lubrication and high-temperature performance.

Best Fit Applications

✅ Dry-running bearings and bushings Where lubricating oil can’t be used — food machinery, medical equipment, high-vacuum environments — bearing-grade PEEK is the most reliable oil-free choice.

✅ Reciprocating seals and piston rings The high PV limit means it tolerates higher contact pressure and sliding velocity, making it a go-to for hydraulic guide rings and seal strips.

✅ Gears, cams, and drive components Self-lubricating behavior makes it ideal for light-to-medium duty drives, with a meaningful noise reduction benefit over metal-on-metal options.

PEEK PTFE: Ultra-Low Friction in Harsh Chemistry

When an application demands both ultra-low friction and extreme chemical resistance — chemical pump seals, dynamic seals in aggressive media — PTFE-modified PEEK offers a unique value proposition:

Friction coefficient as low as 0.05
Good performance in concentrated acids, bases, and organic solvents
Note: mechanical strength is somewhat lower than virgin PEEK; not suitable for high-load structural applications

Medical PEEK: Engineered for the Human Body

Medical-grade PEEK (e.g., Invibio PEEK-OPTIMA) is chemically identical to industrial PEEK, but differentiated by:

Full biocompatibility testing per ISO 10993 and USP Class VI
Full raw material batch traceability
No additives — no antioxidants, stabilizers, or processing aids

For implantable devices, medical-grade certification is non-negotiable. For external medical devices that only contact intact skin, industrial-grade virgin PEEK may qualify after appropriate testing — but confirm with your regulatory team.

Grade Selection Decision Tree

Use these questions to narrow down your options:

1. Medical implant or direct food contact?
   → Yes: Medical PEEK or Virgin PEEK (with appropriate certification)
   → No: Continue

2. Electrical insulation required?
   → Yes: Exclude CF30 (conductive) → Virgin PEEK, GF30, or PEEK PTFE
   → No: CF30 and GF30 both candidates

3. Primary duty: friction/sliding?
   → Yes: FC30 (bearing grade) or CF30 (if strength also critical)
   → No: Continue

4. Highest strength or stiffness the priority?
   → Yes: CF30 (highest specific stiffness)
   → Dimensional stability priority: GF30

5. Aggressive chemical environment with dynamic sealing?
   → Consider PEEK PTFE

Common Selection Mistakes

❌ “More expensive = better”

CF30 costs ~30% more than virgin PEEK, but in static, low-load, or insulation-required applications, virgin PEEK offers better value and easier machining.

❌ “GF30 and CF30 are roughly equivalent”

Their flexural moduli differ by nearly 2× (10 GPa vs. 18 GPa). In high-precision drive components, that gap directly affects system accuracy and vibration behavior.

❌ “Bearing-grade PEEK works everywhere”

FC30’s PTFE content modifies its electrical properties, and PTFE may degrade in certain solvents. In complex chemical environments, verify compatibility before committing.

❌ “PEEK handles any temperature”

PEEK’s continuous use temperature is 260°C — but Heat Deflection Temperature (HDT) under load varies dramatically by grade. Virgin PEEK HDT at 1.82 MPa is roughly 160°C; CF30 exceeds 315°C. For high-temperature structural loads, always check HDT, not just the headline temperature rating.

Summary Table

Primary Need	Recommended Grade
Balanced performance; food/medical use	Virgin PEEK
Maximum strength and stiffness; aerospace structures	CF30
High stiffness + electrical insulation + value	GF30
Low friction; oil-free bearings	FC30 (bearing grade)
Corrosive environment dynamic seals	PEEK PTFE
Implantable medical devices	Medical PEEK (PEEK-OPTIMA, etc.)

About YFT

YFT specializes in PEEK and high-performance engineering plastics — custom machining from raw stock to precision components. Our engineering team provides grade recommendations and material certification support matched to your specific operating conditions.

For samples or selection consultation, contact us anytime.