Polyether ether ketone (PEEK) has established itself as one of the most versatile and high-performance polymers available today. Renowned for its strength, chemical resistance, and dimensional stability at high temperatures, PEEK finds applications in industries ranging from aerospace and medical to oil & gas and semiconductors.
However, the true breadth of PEEK’s capabilities becomes apparent when it is compounded with fillers. By reinforcing the base polymer, engineers can tailor its mechanical and tribological properties to meet highly specific requirements.
This article explores the key filled grades of PEEK, the role of leading global brands, how properties vary across these suppliers, and how new fillers—including graphene—are shaping the future of this remarkable polymer.
Why Fill PEEK?
Unfilled PEEK itself offers excellent mechanical performance, with a tensile strength of ~90–100 MPa, flexural modulus of ~4 GPa, and continuous-use temperature of 250°C. The only other polymer that comes close to PEEK is Polyimide (known by brand names such as Vespel and Kapton). However, at roughly a fourth of the price of Polyimide, PEEK still is the go-to material if the volumes are larger.
Despite its strength and versatility, in demanding applications such as bearings, wear rings, or pump components, certain properties of PEEK need enhancement:
- Wear resistance under high PV (pressure × velocity) conditions
- Stiffness and load-bearing capacity
- Creep resistance at elevated temperatures
- Electrical conductivity or dissipative properties
- Dimensional stability across varying climates
By introducing fillers such as glass fibre, carbon fibre, graphite, PTFE, or newer nanofillers, manufacturers can customise PEEK grades to strike an optimal balance of properties.
The Key Filled Grades of PEEK
1. Glass-Filled PEEK
Glass fibres (typically 30%) enhance tensile strength and flexural modulus, making the material stiffer and more dimensionally stable.
2. Carbon-Fibre Filled PEEK
Carbon fibre reinforcement (typically 30%) significantly boosts strength, stiffness, and thermal conductivity, while reducing creep at high loads.
3. Bearing-Grade (Carbon + Graphite + PTFE)
These blends—often 10% carbon fibre, 10% graphite, and 10% PTFE—are the workhorses of PEEK in dynamic applications.
4. Mineral-Filled PEEK
Some suppliers also offer mineral-filled grades, which provide enhanced dimensional stability and lower CTE without compromising chemical resistance.
Comparison of Filled PEEK Grades Across Brands
Grade Type | Typical Filler Composition | Representative Brands | Key Mechanical Properties | Applications |
|---|
Glass-Filled PEEK | 30% Glass Fibre | Victrex 450GL30, Solvay Ketaspire G30, Ensinger TECAPEEK GF30 | Tensile strength: 130–140 MPa; Flexural modulus: 6–7 GPa; HDT > 315°C | Structural parts, compressor plates, pump housings |
Carbon-Fibre Filled PEEK | 30% Carbon Fibre | Victrex 450CA30, Solvay Ketaspire CA30, Ensinger TECAPEEK CF30 | Tensile strength: 150–170 MPa; Flexural modulus: 11–12 GPa; high thermal conductivity | Aerospace brackets, oil & gas seals, semiconductor components |
Bearing-Grade PEEK | 10% Carbon Fibre, 10% Graphite, 10% PTFE | Victrex 450FC30, Solvay Ketaspire KT-820, Ensinger TECAPEEK PVX | Tensile strength: 90–100 MPa; Coefficient of friction: ~0.1–0.15; outstanding wear resistance | Bearings, bushings, compressor rings, thrust washers, seals |
Mineral-Filled PEEK | 20–30% Mineral Fillers (e.g., silica, talc) | Ensinger TECAPEEK MF series | Enhanced dimensional stability; lower CTE; chemical resistance intact | Precision instruments, thermally cycled environments |
Brand-Level Differences
While most major suppliers—Victrex (UK), Solvay (Belgium/US), Evonik (Germany), and Ensinger (Germany)—offer broadly similar filled grades, there are subtle but significant differences:
- Victrex: Strong in consistency and global certification; often the “go-to” for aerospace and medical due to established approvals.
- Solvay (Ketaspire): Offers broader chemistry options, including higher temperature resistance with specialty grades, and more emphasis on injection mouldable variants.
- Evonik (Vestakeep): Known for toughness and impact resistance, Vestakeep filled grades sometimes exhibit slightly higher elongation compared to peers.
- Ensinger: Being a processor, Ensinger focuses on machinability and availability in stock shapes, making its filled grades ideal for precision machining of prototypes and small batches.
Thus, while datasheet values may appear similar, the differences often show up in secondary properties like machinability, moisture uptake, long-term fatigue, and consistency across batches.
Customisation of PEEK Grades
Beyond standard fillers, many OEMs and compounders now offer custom blends of PEEK tailored to client needs:
- Conductive or dissipative grades (carbon black, CNT-filled) for electronic components and semiconductor applications.
- Radiopaque grades (barium sulfate, tungsten-filled) for medical implants visible under X-ray.
- Low-outgassing grades for space applications.
- Colour-matched grades for medical or consumer-facing devices.
Such customisation allows PEEK to go beyond its conventional role and enter specialised niches that demand both mechanical strength and additional functionality.
New-Age Fillers: Graphene and Beyond
The latest frontier in PEEK compounding is the use of nanofillers such as graphene and carbon nanotubes (CNTs). These materials bring unique enhancements:
- Graphene: Improves electrical conductivity, thermal conductivity, and wear resistance even at very low loadings (<1%). It also enhances stiffness without sacrificing toughness.
- Carbon Nanotubes (CNTs): Deliver ESD (electrostatic dissipative) properties, tensile reinforcement, and improved fatigue resistance.
- Hybrid Fillers: Combinations of graphene, CNTs, and traditional fibres are being explored for aerospace structures, medical implants, and high-end electronics.
While these innovations are still relatively expensive, they demonstrate how PEEK continues to evolve as a polymer platform, adapting to the latest needs in high-performance engineering.
Conclusion
Filled grades of PEEK allow engineers to unlock performance far beyond that of the base resin. From glass- and carbon-fibre reinforcements that boost stiffness and load-bearing capacity, to bearing-grade blends optimised for tribology, each formulation addresses specific application challenges. Variations across brands such as Victrex, Solvay, Evonik, and Ensinger highlight the importance of supplier selection, especially in critical industries like aerospace, medical, and oil & gas.
At the same time, customisation options and the incorporation of advanced fillers like graphene and CNTs point to an exciting future where PEEK not only retains its dominance as a high-performance thermoplastic but also expands into new frontiers of engineering and design.
For manufacturers and end-users alike, understanding these filled grades and their brand-level nuances ensures that PEEK is not just chosen for its name, but for the precise performance it can deliver.
Read More
1. Charting Rulon® Grades and Their Generic Equivalents: A Technical Guide
2. PTFE and the PFAS Debate: Why One Polymer Deserves a Closer Look
3. High-Performance Poppet Valves: The Role of Advanced Polymers in Precision Flow Control
