The diversity of technical applications requires materials that provide optimal performance over a wide temperature range. One of these materials that has the advantage of being a lightweight polymer and at the same time having good properties in high and wide temperature ranges is polyetheretherketone (PEEK).
PEEK is used in many areas of engineering to achieve performance and demanding applications similar to metals. Many applications that require high compressive, wear and tensile strength with high performance, such as the oil and gas industry, can take advantage of all the potential benefits that PEEK materials have to offer.
What is PEEK?
Polyetheretherketone (PEEK), commonly called PEEK, is a colorless organic thermoplastic with mechanical and chemical properties suitable for numerous technical applications. It belongs to the family of polyaryl ether ketones (PAEK) polymers.
It is usually prepared by step polymerization. PEEK is more expensive compared to other polymers, but offers superior performance across multiple dimensions. PEEK offers excellent wear and abrasion resistance, which is desirable in many areas of engineering.
PEEK material properties
Peek polymers exhibit chemical resistance as well as physical properties, tensile strength and dimensional stability; therefore, the mechanical properties offer resistance to high temperatures.
1. High temperature resistance
PEEK with high performance technical thermoplastic is a modern thermoplastic material resistant to high temperatures.
In addition to its high performance and thermal conductivity, PEEK can maintain its high operating temperature strength even at very high temperatures, achieving a high glass transition temperature of 143 degrees Celsius and a high melting point (334 °C).
It can withstand short-term working temperatures of up to 300°C and can be permanently exposed to high temperatures of 250°C. This is one reason why PEEK materials can be used where heat resistance is an important issue.
2. Good mechanical properties
PEEK has the best fatigue resistance of all resins. The combination of excellent mechanical strength and fatigue resistance properties is the most outstanding of all plastics. The performance is in no way inferior to that of some alloys, hence the mechanical properties. Because the mechanical strength remains constant under all processing conditions.
3. Wear resistance and lubricity
PEEK or polyetheretherketone-PEEK polymers and their composites exhibit excellent wear resistance, with some types of PEEK exhibiting extremely low friction and wear coefficients.
Polyetheretherketone-Peek has excellent sliding properties, especially in the storage area. Its own sliding properties significantly reduce the coefficient of friction or the so-called low coefficient, allowing certain parts to function without lubricants and also in media such as water, weak acids and bases.
4. Chemical resistance (corrosion resistance)
Polyetheretherketone peek has stable chemical resistance. It is chemically resistant to chemicals, acids, concentrated sulfuric acid, alkalis, organic solvents and other chemicals and various atmospheres.
PEEK is corrosion resistant. Corrosion resistance generally refers to the metal's ability to resist the corrosive and destructive effects of the surrounding environment.
PEEK belongs to the field of PEEK plastics and polymeric materials. Its material composition, chemical properties, organization and morphology determine that it can improve intergranular corrosion, improve corrosion resistance, and compare corrosion resistance with that of nickel steel.
5. Flame Retardation
PEEK is a linear aromatic semi-crystalline polymer with inherent flame retardant properties.
Peek polyetheretherketone has been tested for flame retardancy (UL94 test, vertical burn rate test and self-extinguishing time test) and a 1.45mm sample without additives has a burn rate of V-0, which is the highest level of flame retardancy.
PEEK is used in construction materials, vehicles and equipment that require high flame retardancy and use in aqueous environments.
6. Peeling strength
PEEK has good peel resistance. It can be used to produce very thin coiled wires or electromagnetic wires, as well as cable insulation, which can be used in harsh environments and conditions.
7. Radiation resistance
PEEK materials maintain their original performance when exposed to gamma irradiation. Its resistance to gamma irradiation is very strong, and many polymer materials maintain stable performance even after irradiation.
This is more than polystyrene's better irradiation resistance than general-purpose resin. With a γ radiation dose of 1100 Mrad, the good insulation capacity of the high-performance wire can still be maintained.
8. Hydrolysis resistance
PEEK and its composite materials are not chemically affected by water and water vapor under high pressure, and products made from this material can maintain their excellent properties even when used continuously in water at high temperatures and high pressure.
Three types of PEEK material processing
One of the reasons for the widespread use of PEEK in engineering applications is the availability of numerous processing options and conditions, namely machining, melt deposition, 3D printing and injection molding, to produce the desired geometry in organic and aqueous environments.
PEEK materials are available in rod form, compressor plate valves, filament form and granules for use in machining, 3D printing and injection molding. The following sections provide relevant details about all three manufacturing processes.
PEEK CNC machining
CNC (Computer Numerical Control) machining consists of different variants of multi-axis milling, turning and electrical discharge machining (EDM) to obtain the desired geometric profile. The main advantage of these machines is the ability to control the machine through computer-generated code using advanced controls.
CNC machining offers the ability to create complex geometries while maintaining required geometric tolerance limits on a variety of materials, from plastics to metals. Molded parts made from PEEK materials can be machined to obtain complex geometric profiles. Medical and industrial grade PEEK can be processed. PEEK machining offers high precision and repeatability.
Due to PEEK's high melting point, faster feed rates and higher speeds can be used during the machining process compared to other polymers. Before starting the machining process, special annealing requirements must be met to avoid internal stresses and heat-induced cracks during machining. These requirements differ depending on the type of PEEK material used. Detailed information on this is provided by the manufacturer of the respective variety.
PEEK is significantly stronger and stiffer than most polymers, but softer than most metals. This requires the use of fixtures during machining to ensure accurate machining. PEEK, a highly heat-resistant technical plastic, does not adequately dissipate the heat generated during the machining process. Therefore, techniques must be used to avoid problems due to inadequate heat dissipation through the material.
These preventive measures include deep drilling, coolant-fed drills, and the use of sufficient coolant during all machining operations. Both mineral oil and water-based coolants can be used.
Another important factor to consider is tool wear when machining PEEK compared to machining other less compatible plastics. Carbon fiber reinforced PEEK grades have a more damaging effect on tools. This situation requires the use of carbide tools to machine a normal PEEK grade and diamond tools for carbon fiber reinforced PEEK grades. Using coolant can also improve tool life.
PEEK 3D Printing
3D printing, also known as additive manufacturing, generally refers to adding material layer by layer to create three-dimensional geometry from a computer-aided design model.
PEEK material is suitable for 3D printing. Fused deposition modeling (FDM) is the most widely used 3D printing process for PEEK material. There is also some progress in printing PEEK powder using Selective Laser Sintering (SLS).
3D printed PEEK products offer excellent abrasion and wear resistance. Filaments from different manufacturers may have different properties. 3D printed parts offer medical professionals a unique opportunity to create customized implants that meet patients' individual needs. 3D printed parts made from PEEK material are used in various space systems. This performance is a testament to the power of 3D printed PEEK.
However, printing PEEK material requires a high temperature nozzle above 300°C. In addition to the high temperature nozzle, a heated bed is required to continuously keep the material heated. Some printers also use heated chambers for this purpose. Heated chambers provide greater control over chamber temperature and ensure even heat release.
PEEK injection molding
Injection molding is the production of thermoplastic parts by injecting molten material into existing molds. It is used to produce parts in large quantities. The material is melted in a heated chamber, the spiral screw is used to mix and then injected into the mold cavity where the material is cooled to form a solid form.
PEEK materials in granular form are used for injection molding and compression molding. PEEK in granular form produced by different manufacturers requires slightly different drying procedures, but generally 3 to 4 hours of drying at 150°C to 160°C is sufficient.
Standard injection molding machines can be used to mold PEEK or Moldpeek materials, as these machines reach a heating temperature of 350°C to 400°C, which is sufficient for almost all types of PEEK.
Mold cooling requires special attention, as any inconsistency can lead to a change in the structure of the PEEK material. Any deviation from the semi-crystalline structure leads to an undesirable change in the characteristic properties of PEEK.
For example, a cold mold can lead to the formation of an amorphous structure in PEEK. The ideal mold operating temperature for most grades of PEEK is between 170°C and 200°C to achieve a semi-crystalline structure.
Where Peek Material Is Used
1. Medicine
Due to PEEK's biocompatible properties, it is widely used in medical applications, including implanting parts into the human body for various periods of time. Parts made from PEEK material are also used in various drug delivery systems.
Other medical applications include dental caps, pointed washers, trauma fixation devices, and spinal fusion devices.
2. Aerospace
Due to PEEK's compatibility with ultra-high vacuum applications, its thermal conductivity, and radiation and chemical resistance, PEEK plastic parts are widely used in aerospace applications due to their high tensile strength.
3. Automotive industry
Bearings and various types of rings are also made from PEEK. Due to PEEK's better strength-to-weight ratio, it is used to manufacture parts used in racing car engine blocks.
4. Insulation of wires and cables/electronic applications
Electrical cable insulation is manufactured from PEEK for use in applications such as aircraft electrical systems in manufactured articles.
5. Future applications
After being approved by the US Food and Drug Administration (FDA) for all processing conditions, PEEK also has a promising future in the food industry.
University Degree
As a semi-crystalline organic polymer from the PAEK family, PEEK offers mechanical, thermal, chemical and electrical properties that make it a material of choice in numerous areas of technical applications. PEEK is available in several forms (rod, filament, granulated) and can be processed by machining, 3D printing and injection molding. WayKen has extensive experience in PEEK machining and is ready to assist you with your PEEK projects. Feel free to request an offer.
