Diversity in engineering applications calls for materials that can perform optimally over a wide range of temp conditions. One such material bearing the benefit of being a lightweight polymer in addition to bearing good properties at high and broad temperature ranges is Polyetheretherketone (PEEK).
In multiple domains of engineering, PEEK is used to achieve performance and demanding applications similar to that delivered by metals. Multiple applications demanding long-term pressure and wear excellent resistance along tensile strength with high performance such as those in the oil and gas industry can leverage all of the potential benefits that PEEK materials have to offer.
What is PEEK?
Polyetheretherketone PEEK commonly referred to as PEEK is a colorless organic thermoplastic polymer with mechanical and chemical properties that suits wide-ranging engineering applications. It belongs to polyaryletherketone (PAEK) family of polymers.
It is generally manufactured through step-growth polymerization. PEEK is more expensive as compared to other polymers but offers superior performance along multiple dimensions. PEEK offers excellent wear and abrasion resistance that is desirable across multiple domains of engineering.
PEEK Materials Properties
Peek Polymers has chemical resistance properties along with physical properties, tensile strength, dimensional stability, hence the mechanical properties offer high temperature performance.
1. High temperatures resistance
PEEK with high performance engineering thermoplastic is a high temperature resistant advanced thermoplastic material.
As with high performance along with thermal conductivity even at very high temperatures PEEK can maintain high strength with operating temperature and can reach a high glass transition temperature of 143 degrees Celsius and melting point (334°C).
It can withstand short-term working temperatures of up to 300°C and continuously use high temperatures of 250°C. This is one of the reasons why PEEK materials can be used where heat resistance is a concern.
2. Good mechanical properties
PEEK has the best fatigue resistance of any resin, and the combination of excellent mechanical strength properties and fatigue resistance is the most outstanding of all plastics, with performance not inferior to that of some alloys with hence the mechanical properties. As the mechanical strength is continuous in all processing conditions.
3. Wear resistance and lubricity
PEEK polymers or polyetheretherketone peek and their composites all have excellent wear resistance, with some PEEK having extremely low coefficients of friction and wear.
Polyetheretherketone peek has excellent sliding characteristics, especially in the bearing field. Its own sliding properties greatly reduce the coefficient of friction or known as a low coefficient, allowing certain parts to operate without lubricants and also in media such as water, weak acids, and alkalis.
4. Chemical resistance (corrosion resistance)
Polyetheretherketone peek has a stable chemical resistance. It is chemically resistant to chemicals, acids, concentrated sulfuric acid, alkalis, organic solvents and other chemicals, and various atmospheres.
PEEK has corrosion resistance, corrosion resistance usually refers to the ability of the metal to resist the corrosive and destructive effects of surrounding media.
PEEK belongs to the field of Peek plastic and polymer materials, its material composition, chemical properties, organization and morphology determine it can improve intergranular corrosion, improve corrosion resistance, corrosion resistance and nickel steel are similar.
5. Flame resistance
PEEK is a linear aromatic semi-crystalline polymer with its own flame retardant properties.
Polyetheretherketone peek has been tested for flame retardancy (UL94 test, vertical burn rate test and self-extinguishing time test), and a 1.45mm sample without any additives has a burn rate of V-0, which is the highest flame retardancy level.
PEEK is used in building materials, vehicles and appliances that require high flame retardancy and aqueous environments.
6. Peel resistance
PEEK has good peel resistance. It can be used to make a very thinly wrapped wire or electromagnetic wire, cable insulation, which can be applied under harsh environments and conditions.
7. irradiation resistance
PEEK materials in the role of gamma radiation to maintain their original performance, the ability to resist gamma irradiation is very strong, many polymer materials after radiation can still maintain stable performance.
This is more than the general-purpose resin in the best resistance to irradiation of polystyrene. When it be made into γ irradiation dose of 1100Mrad can still maintain good insulation capacity of the high-performance wire.
8. Hydrolysis resistance
PEEK and its composites are not chemically affected by water and high-pressure water vapor, and products made from this material can maintain excellent properties when used continuously in high-temperature and high-pressure water.
Three types of PEEK material machining
One of the reasons behind the widespread use of PEEK in engineering applications is the availability of multiple options and processing conditions, namely machining, fused filament fabrication, 3D printing, and injection molding for manufacturing desired geometry in organic and aqueous environments.
PEEK materials are available in the rod form, compressor plate valves, filament form, and granular form for usage in machining, 3D printing, and injection molding respectively. The following sections provide relevant details for all three of these manufacturing methods.
PEEK CNC machining
CNC (Computer Numeric Control) machining consists of different variants of multi-axis milling, turning, and Electric Discharge machines (EDM) to obtain desired geometric profile. The main advantage of these machines originates from the ability to control the machine through computer-generated code through advanced controllers.
CNC machining offers the opportunity to create geometries, which are complex while meeting the required geometric tolerance limits, of different materials ranging from plastics to metals. Mold PEEK materials can be machined to obtain complex geometric profiles. Medical grade, as well as industrial grade PEEK, can be machined. PEEK machining provides high accuracy and repeatability.
Due to the high melting point of PEEK, faster feed rates and speed can be employed during the machining process as compared to other polymers. Before starting the machining process, there are special annealing requirements that must be met to avoid internal stress and heat-related cracks during machining. These requirements differ based on the grade of PEEK materials being used and complete details in this regard are provided by the manufacturer of that certain grade.
PEEK is considerably stronger and stiffer than most polymers, but softer than most metals. This necessitates the usage of fixtures during machining to ensure accurate machining. PEEK, high-heat engineering plastic, does not dissipate the heat produced during the machining process adequately. That calls for employing techniques to avoid problems due to inefficient heat dissipation by the material.
These preventive measures include peck drilling, coolant-fed drill bits, and the usage of enough coolant during all of the machining processes. Both petroleum-based and water-based coolants can be used.
Another important factor to consider is tool abrasion during machining PEEK as compared to machining other few Plastics compatible. PEEK grades that are reinforced using carbon fiber have a more adverse effect on tools. This situation demands for use of carbide-tipped tools for machining of a normal grade of PEEK and diamond-tipped tools for carbon fiber reinforced PEEK grades. Usage of coolant can improve tool life as well.
PEEK 3D printing
3D printing, also known as additive manufacturing, generally refers to the use of the addition of material in form of layers to create a 3-dimensional geometry from a Computer-Aided Design model.
PEEK material lends itself to 3D printing. Fused Deposition Modelling (FDM) is the most widely used 3D printing method for PEEK material. There is also some progress being made to print PEEK in powdered form through Selective Laser Sinter (SLS).
3D printed PEEK products offer excellent abrasion and wear resistance. Filament produced by different manufacturers can offer different properties. 3D printed parts offer a unique opportunity for medical professionals to produce customized implants to meet individual patients’ needs. 3D printed PEEK material parts are in service on different space systems. This feat serves as proof of the capabilities that 3D-printed PEEK has to offer.
However, to print PEEK material a high temp nozzle having a temperature of more than 300 °C is required. In addition to the high-temperature nozzle, a heated bed is required to continuously keep the material in a heated state. Some printers use the heated chambers for this purpose as well. Heated chambers provide better control over the chamber temperature and provide heat consistently.
PEEK injection molding
Injection molding refers to the manufacturing of thermoplastic parts through injecting molten material in pre-existing molds. It is used to manufacture parts in a large number. Material is melted in a heated chamber, the helical screw is used for mixing and then injecting into the mold cavity where the material is cooled to form a solid shape.
PEEK materials bring in granular form is used for injection and compression molding. PEEK in granular form produced by different manufacturers require slightly different drying procedure but in general, 3 to 4 hours of drying at 150 °C to 160 °C will suffice.
Standard injection molding machines can be used for injection molding of PEEK materials or mold peek, as these machines can reach a heating temperature of 350 °C to 400 °C which is sufficient for almost all of the PEEK grades.
Cooling of the mold requires special attention as any inconsistency can lead to a change in the structure of PEEK material. Any deviation from the semi-crystalline structure leads to an undesirable change in signature properties of PEEK.
For example, having a cold mold can lead to the creation of the amorphous structure in PEEK. The optimum mold operating temperature for most grades of PEEK is considered to be between 170 °C to 200 °C to obtain a semi-crystalline structure.
Where Peek material is Used
Due to the biocompatible properties that PEEK has to offer, it is widely used in medical applications that also include implanting parts in the human body for different periods of time. Parts made of PEEK material are also used in different drug delivery systems.
Other medical applications include dental healing caps, spiked washers, trauma fixation devices, and spinal fusion devices.
Due to the compatibility of PEEK with ultra-high vacuum applications, thermal conductivity and radiation and chemical resistance, parts made from PEEK plastic are widely used in aerospace applications due to their high performance tensile strength.
3. Automotive Industry
Bearings and different types of rings are also made from PEEK. Due to the superior weight-to-strength ratio of PEEK, it is used to manufacture parts that are to be used in engine blocks of racing cars.
4. Wire and cable insulation/electronic applications
Electrical cable insulations are made from PEEK to be used in applications like electrical systems of airplanes in Fabricate items.
5. Future applications
PEEK has a high and bright future in the food industry as well after the approval of US food and drug administration in all processing conditions.