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What Is PEEK?
Polyetheretherketone (PEEK) is a high-performance engineering thermoplastic polymer esteemed for its exceptional mechanical, thermal, and chemical properties. Capable of withstanding high temperatures, it excels in harsh environments and demanding applications, making it a popular choice in the aerospace, automotive, medical, and electronics industries.
Key Peek Properties and Their Benefits
High Mechanical Strength and Stiffness
High mechanical strength refers to a material’s stress-bearing capacity before permanent deformation or breaking point. PEEK has a tensile strength of 90-100 MPa (unfilled), much higher than other thermoplastics, crucial for high-pressure or heavy-load applications. The high strength ensures structural integrity. PEEK’s mechanical properties are critical in these situations, with fatigue resistance being an essential factor.
Stiffness, on the other hand, is a measure of a material’s resistance to bending or flexing when subjected to an external force. PEEK exhibits high stiffness, with a tensile modulus of around 3.5-4.1 GPa (unfilled). This means that PEEK components are less likely to deform or change shape under load, maintaining their dimensional stability even in challenging environments. The stiffness of PEEK is another essential aspect of its mechanical properties that contributes to its overall performance.
These properties of high mechanical strength and stiffness contribute to PEEK’s overall durability and reliability, hence the mechanical properties of this material are of paramount importance. As a result, PEEK is often used in applications where the material is expected to endure high stress or forces, such as aerospace components, automotive parts, medical devices, gears, and bushings. Additionally, PEEK’s high strength-to-weight ratio makes it an attractive alternative to metals in weight-sensitive applications, further showcasing the significance of its mechanical properties.
Superior Thermal Resistance
PEEK’s superior thermal resistance makes it an ideal material for high-performance applications under extreme temperatures. Its broad operating temperature range, from cryogenic levels up to 480°F (250°C), allows PEEK to maintain its mechanical and chemical properties even in demanding conditions. This broad temperature range provides PEEK with high-temperature stability, making it a reliable choice for industries such as aerospace, automotive, and electronics, where components must operate in varying and often harsh thermal environments. The operating temperature range of PEEK is a critical aspect of its thermal properties and highlights the material’s exceptional ability to perform reliably in extreme conditions.
Exceptional Chemical Resistance
PEEK’s exceptional chemical resistance properties make it a highly sought-after material in industries where components are exposed to a variety of harsh chemicals, solvents, and corrosive environments. This high-performance engineering thermoplastic maintains its structural integrity and dimensional stability even when subjected to a wide range of aggressive chemicals, including acids, bases, and hydrocarbons. The outstanding chemical resistance properties of PEEK ensure that components made from this material will not deteriorate, swell, or degrade when exposed to such substances, making it an ideal choice for applications in the chemical processing, oil and gas, and medical industries.
Low Moisture Absorption
PEEK’s low moisture absorption is a notable property that makes it suitable for applications in both organic and aqueous environments. The material’s ability to resist absorbing water or other fluids is critical in maintaining its mechanical, thermal, and electrical properties in various conditions. When exposed to moisture, PEEK exhibits minimal swelling, ensuring the dimensional stability of components manufactured from this high-performance engineering thermoplastic. This characteristic is particularly important in industries such as electronics, where maintaining consistent electrical properties is vital, or in applications where components are subjected to fluctuating humidity levels or submerged in liquids. PEEK’s low moisture absorption allows for reliable, long-lasting performance in challenging environments.
Excellent Wear and Friction Properties
PEEK’s sliding properties greatly reduce friction and wear, making it a sought-after material for moving parts in contact with each other. The unique molecular structure of this high-performance thermoplastic offers inherent lubricity, extending the service life of components and reducing wear and tear. These properties make PEEK an ideal material for applications that demand superior sliding properties and durability.
Biocompatibility and FDA Compliance
PEEK’s biocompatibility and FDA compliance make it an ideal choice for medical applications. Its non-toxic nature and compatibility with human tissues allow it to be used safely in implants and other medical devices. PEEK’s resistance to chemicals and sterilization processes further enhances its suitability for medical applications, as it maintains its properties even after repeated sterilizations, meeting FDA regulations and ensuring patient safety.
Electrical Insulation
PEEK’s high dielectric strength and low dielectric constant make it an excellent insulator, while its ability to withstand high temperatures allows it to maintain its electrical properties in harsh environments. These properties, combined with PEEK’s mechanical and chemical resistance, make it a popular choice for electrical components in the aerospace, automotive, and electronics industries.
Low Outgassing
Low outgassing is an essential property of PEEK, particularly in applications where the release of smoke and toxic gas could be harmful or compromise the integrity of the surrounding environment. Outgassing refers to the release of volatile compounds from materials when they are exposed to heat, vacuum, or other conditions. PEEK’s low outgassing characteristics make it a suitable choice for applications in sensitive environments, such as electronics, aerospace, and semiconductor manufacturing, where contamination control is critical.
PEEK’s low outgassing properties help maintain the cleanliness of the environment in which it is used, ensuring that the performance and longevity of the components made from this material are not compromised by the release of potentially harmful or reactive gases. Additionally, low outgassing contributes to improved safety in applications where the presence of smoke or toxic gas could pose a hazard to people or equipment.
Grades of Peek and Their Properties
| Grades of PEEK | Characteristic | Advantage | Disadvantage |
|---|---|---|---|
| Unfilled PEEK | Pure PEEK, without fillers, for maximum elongation and toughness | Suitable for food contact and medical applications, with good fatigue resistance and chemical stability | Lower strength and stiffness |
| Glass-filled PEEK | PEEK with 30% glass fiber for increased flexural modulus and reduced expansion | Suitable for structural applications where increased strength, stiffness, or stability is required, especially in high temperature environments | Low resistance to abrasion and toughness, light brown color only |
| Carbon-filled PEEK | PEEK with 30% carbon fiber for increased compression strength and stiffness and significantly reduced expansion | Suitable for applications requiring optimum wear resistance and load-carrying capacity, with 3.5 times the thermal conductivity of non-reinforced PEEK | Higher price, color only black |
| Bearing-grade PEEK | PEEK with carbon fiber, graphite, and polytetrafluoroethylene (PTFE) provides the best coefficient of friction and wear resistance | Suitable for applications requiring low friction and high wear resistance such as bearings, sliding parts, seals, etc. | Lower strength and stiffness, higher price |
| PEEK-CA30 | PEEK with 30% carbon fiber, similar to Carbon-filled PEEK, but with better creep resistance and lower moisture absorption | Suitable for applications requiring high strength, high stiffness, high wear resistance, and low expansion, especially in wet environments | Higher price, color only black |
| Medical-grade PEEK | Specially treated PEEK that meets medical grade requirements, is biocompatible and non-toxic | For medical devices, implants, surgical procedures, and other applications requiring high purity and safety | Higher price, color only light brown |
Unfilled PEEK
This is the purest form of PEEK, offering the highest level of mechanical and chemical properties.
Glass-filled PEEK
Glass fibers are added to the base PEEK polymer, resulting in increased rigidity, strength, and dimensional stability. Glass-filled PEEK offers better wear resistance and lower creep compared to unfilled PEEK. This variant is ideal for applications where structural integrity and dimensional stability are essential, such as gears, seals, and bushings.
Carbon-Filled Peek
Carbon fibers are incorporated into the PEEK matrix, enhancing its mechanical strength, stiffness, and wear resistance. Carbon-filled PEEK also has lower thermal expansion and improved electrical conductivity, making it suitable for high-load, high-wear applications in industries such as aerospace, automotive, and electronics.
Bearing-Grade PEEK
Bearing-grade PEEK is a high-performance polymer designed for sliding or rotating parts, such as bearings, bushings, and seals. With improved wear resistance, lower friction, and superior load-carrying capacity, it excels in high temperature applications where metal bearings would fail. As a result, Bearing-grade PEEK is a top choice for demanding applications that require excellent performance and reliability.
PEEK-CA30
PEEK-CA30 is a blend of PEEK and 30% carbon fibers, which offers a combination of high strength, stiffness, and excellent wear resistance. This material is ideal for applications that require a balance between mechanical performance and lightweight characteristics, such as aerospace components and automotive parts.
Medical-Grade Peek
Medical-grade PEEK is specifically designed to meet the stringent requirements of medical applications, such as implants and surgical instruments. It exhibits excellent biocompatibility, sterilization resistance, and radiolucency, making it a preferred choice in the medical field.
Top PEEK Material Processing Methods: Exploring Common Techniques
Injection Molding
Injection molding is a common method for processing PEEK, where the material is heated, melted, and injected into a mold cavity under high pressure. Once cooled, the solidified part is ejected from the mold. This method is suitable for high-volume production of complex parts with tight tolerances, such as gears, connectors, and housings.
Extrusion
Extrusion involves heating PEEK and forcing it through a shaped die to create continuous lengths of material with a specific cross-sectional profile. The extruded material can be in the form of rods, tubes, sheets, or custom profiles. Extrusion is commonly used for manufacturing semi-finished PEEK products, which can be further processed into final components.
Compression Molding
Compression molding is a technique where PEEK is heated and compressed between two heated mold halves. The material softens, fills the mold cavity, and solidifies upon cooling. Compression molding is suitable for producing large, complex parts with low to moderate production volumes, such as seals, gaskets, and valve components.
CNC Machining
CNC machining, or Computer Numerical Control machining, is a subtractive manufacturing process that uses computer-controlled machines to precisely remove material from a workpiece, creating a finished part. It is one of the most widely used manufacturing techniques due to its high precision, versatility, and ability to produce complex geometries. CNC machining is particularly well-suited for the production of small to medium-sized batches of parts, prototypes, and one-offs.
CNC machining offers numerous benefits, including:
- High precision and tight tolerances
- Ability to produce complex geometries and intricate details
- Broad range of compatible materials, including metals, plastics, and composites
- Excellent repeatability and consistency across multiple parts
- Relatively low setup costs and shorter lead times compared to other manufacturing processes
3D Printing
3D printing, or additive manufacturing, is a relatively new technique for processing PEEK. It involves building a part layer by layer, using a 3D printer that melts and extrudes PEEK filament or powder. This method enables the production of complex geometries that are difficult or impossible to achieve using traditional manufacturing methods. 3D printing is ideal for creating custom parts, prototypes, and low-volume production.
| Processing Method | Tooling Cost | Production Speed | Material Waste | Design Flexibility | Surface Finish | Tolerances |
|---|---|---|---|---|---|---|
| Injection Molding | High | Fast | Low | Moderate | Good | Tight |
| Extrusion | Moderate | Fast | Low | Limited | Good | Moderate |
| Compression Molding | Moderate | Moderate | Low | Limited | Good | Moderate |
| CNC Machining | Low | Fast | High | High | Excellent | Tight |
| 3D Printing | Low | Slow | Moderate | High | Fair to Good | Moderate |
Comparing Peek Properties to Alternative Materials
| Property | PEEK | PTFE (Teflon) | PAI (Torlon) | PAI (Torlon) | PBI (Celanex) |
|---|---|---|---|---|---|
| Density (g/cm³) | 1.3-1.45 | 2.2 | 1.4 | 1.35 | 1.3 |
| Tensile Strength (MPa) | 90-100 | 20-35 | 103-207 | 75-100 | 150-220 |
| Elongation at Break (%) | 10-50 | 200-350 | 5-6 | 2.5-5 | 3.5-6 |
| Flexural Modulus (GPa) | 3.5-4.5 | 0.5 | 3.5-4.5 | 3-3.5 | 3.5-4.5 |
| Continuous Service Temp. (°C) | -60 to 260 | -240 to 260 | -60 to 270 | -60 to 220 | -60 to 310 |
| Thermal Conductivity (W/mK) | 0.25-0.8 | 0.25 | 0.3 | 0.3 | 0.45 |
| Thermal Conductivity (W/mK) | 20-25 | 60 | 20-25 | 20-25 | 25-30 |
| Chemical Resistance | Excellent | Excellent | Excellent | Excellent | Excellent |
| Moisture Absorption | Low | Low | Low | Low | Low |
| Biocompatibility | Excellent | Good | Good | Good | Good |
PEEK vs. other high-performance polymers: PEEK’s combination of mechanical, thermal, and chemical properties sets it apart from other high-performance polymers, such as PPS, PTFE, and PAI. Its superior properties make it suitable for use in a wider range of applications and environments.
Conclusion: Unlocking the potential of PEEK properties for your project
PEEK’s unique combination of high-performance properties makes it an ideal material for a variety of applications across multiple industries. By understanding the specific properties of PEEK and its variants, you can make informed decisions about which PEEK grade is best suited for your project. In addition, utilizing the most appropriate processing method for PEEK will help ensure that you get the most out of this versatile material. Whether you require high mechanical strength, thermal resistance, chemical resistance, or a combination of these properties, PEEK offers numerous advantages that can help you achieve your project goals.
AT-Machining is a one-stop shop for all your CNC machining needs. Our advanced equipment, skilled workforce, and stringent quality control measures ensure that every part we produce meets the highest standards of precision and durability. We are dedicated to providing our customers with the best possible machining solutions by leveraging our extensive material options and finishing services. Trust AT-Machining with your next project, and experience the difference that our expertise and commitment to quality can make.
